Adding upstream version 1:2.39.2.upstream/1%2.39.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 5131 insertions, 0 deletions

diff --git a/merge-ort.c b/merge-ort.c
new file mode 100644
index 0000000..d1611ca
--- /dev/null
+++ b/merge-ort.c
@@ -0,0 +1,5131 @@
+/*
+ * "Ostensibly Recursive's Twin" merge strategy, or "ort" for short.  Meant
+ * as a drop-in replacement for the "recursive" merge strategy, allowing one
+ * to replace
+ *
+ *   git merge [-s recursive]
+ *
+ * with
+ *
+ *   git merge -s ort
+ *
+ * Note: git's parser allows the space between '-s' and its argument to be
+ * missing.  (Should I have backronymed "ham", "alsa", "kip", "nap, "alvo",
+ * "cale", "peedy", or "ins" instead of "ort"?)
+ */
+
+#include "cache.h"
+#include "merge-ort.h"
+
+#include "alloc.h"
+#include "attr.h"
+#include "blob.h"
+#include "cache-tree.h"
+#include "commit.h"
+#include "commit-reach.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "dir.h"
+#include "entry.h"
+#include "ll-merge.h"
+#include "object-store.h"
+#include "promisor-remote.h"
+#include "revision.h"
+#include "strmap.h"
+#include "submodule-config.h"
+#include "submodule.h"
+#include "tree.h"
+#include "unpack-trees.h"
+#include "xdiff-interface.h"
+
+/*
+ * We have many arrays of size 3.  Whenever we have such an array, the
+ * indices refer to one of the sides of the three-way merge.  This is so
+ * pervasive that the constants 0, 1, and 2 are used in many places in the
+ * code (especially in arithmetic operations to find the other side's index
+ * or to compute a relevant mask), but sometimes these enum names are used
+ * to aid code clarity.
+ *
+ * See also 'filemask' and 'dirmask' in struct conflict_info; the "ith side"
+ * referred to there is one of these three sides.
+ */
+enum merge_side {
+	MERGE_BASE = 0,
+	MERGE_SIDE1 = 1,
+	MERGE_SIDE2 = 2
+};
+
+static unsigned RESULT_INITIALIZED = 0x1abe11ed; /* unlikely accidental value */
+
+struct traversal_callback_data {
+	unsigned long mask;
+	unsigned long dirmask;
+	struct name_entry names[3];
+};
+
+struct deferred_traversal_data {
+	/*
+	 * possible_trivial_merges: directories to be explored only when needed
+	 *
+	 * possible_trivial_merges is a map of directory names to
+	 * dir_rename_mask.  When we detect that a directory is unchanged on
+	 * one side, we can sometimes resolve the directory without recursing
+	 * into it.  Renames are the only things that can prevent such an
+	 * optimization.  However, for rename sources:
+	 *   - If no parent directory needed directory rename detection, then
+	 *     no path under such a directory can be a relevant_source.
+	 * and for rename destinations:
+	 *   - If no cached rename has a target path under the directory AND
+	 *   - If there are no unpaired relevant_sources elsewhere in the
+	 *     repository
+	 * then we don't need any path under this directory for a rename
+	 * destination.  The only way to know the last item above is to defer
+	 * handling such directories until the end of collect_merge_info(),
+	 * in handle_deferred_entries().
+	 *
+	 * For each we store dir_rename_mask, since that's the only bit of
+	 * information we need, other than the path, to resume the recursive
+	 * traversal.
+	 */
+	struct strintmap possible_trivial_merges;
+
+	/*
+	 * trivial_merges_okay: if trivial directory merges are okay
+	 *
+	 * See possible_trivial_merges above.  The "no unpaired
+	 * relevant_sources elsewhere in the repository" is a single boolean
+	 * per merge side, which we store here.  Note that while 0 means no,
+	 * 1 only means "maybe" rather than "yes"; we optimistically set it
+	 * to 1 initially and only clear when we determine it is unsafe to
+	 * do trivial directory merges.
+	 */
+	unsigned trivial_merges_okay;
+
+	/*
+	 * target_dirs: ancestor directories of rename targets
+	 *
+	 * target_dirs contains all directory names that are an ancestor of
+	 * any rename destination.
+	 */
+	struct strset target_dirs;
+};
+
+struct rename_info {
+	/*
+	 * All variables that are arrays of size 3 correspond to data tracked
+	 * for the sides in enum merge_side.  Index 0 is almost always unused
+	 * because we often only need to track information for MERGE_SIDE1 and
+	 * MERGE_SIDE2 (MERGE_BASE can't have rename information since renames
+	 * are determined relative to what changed since the MERGE_BASE).
+	 */
+
+	/*
+	 * pairs: pairing of filenames from diffcore_rename()
+	 */
+	struct diff_queue_struct pairs[3];
+
+	/*
+	 * dirs_removed: directories removed on a given side of history.
+	 *
+	 * The keys of dirs_removed[side] are the directories that were removed
+	 * on the given side of history.  The value of the strintmap for each
+	 * directory is a value from enum dir_rename_relevance.
+	 */
+	struct strintmap dirs_removed[3];
+
+	/*
+	 * dir_rename_count: tracking where parts of a directory were renamed to
+	 *
+	 * When files in a directory are renamed, they may not all go to the
+	 * same location.  Each strmap here tracks:
+	 *      old_dir => {new_dir => int}
+	 * That is, dir_rename_count[side] is a strmap to a strintmap.
+	 */
+	struct strmap dir_rename_count[3];
+
+	/*
+	 * dir_renames: computed directory renames
+	 *
+	 * This is a map of old_dir => new_dir and is derived in part from
+	 * dir_rename_count.
+	 */
+	struct strmap dir_renames[3];
+
+	/*
+	 * relevant_sources: deleted paths wanted in rename detection, and why
+	 *
+	 * relevant_sources is a set of deleted paths on each side of
+	 * history for which we need rename detection.  If a path is deleted
+	 * on one side of history, we need to detect if it is part of a
+	 * rename if either
+	 *    * the file is modified/deleted on the other side of history
+	 *    * we need to detect renames for an ancestor directory
+	 * If neither of those are true, we can skip rename detection for
+	 * that path.  The reason is stored as a value from enum
+	 * file_rename_relevance, as the reason can inform the algorithm in
+	 * diffcore_rename_extended().
+	 */
+	struct strintmap relevant_sources[3];
+
+	struct deferred_traversal_data deferred[3];
+
+	/*
+	 * dir_rename_mask:
+	 *   0: optimization removing unmodified potential rename source okay
+	 *   2 or 4: optimization okay, but must check for files added to dir
+	 *   7: optimization forbidden; need rename source in case of dir rename
+	 */
+	unsigned dir_rename_mask:3;
+
+	/*
+	 * callback_data_*: supporting data structures for alternate traversal
+	 *
+	 * We sometimes need to be able to traverse through all the files
+	 * in a given tree before all immediate subdirectories within that
+	 * tree.  Since traverse_trees() doesn't do that naturally, we have
+	 * a traverse_trees_wrapper() that stores any immediate
+	 * subdirectories while traversing files, then traverses the
+	 * immediate subdirectories later.  These callback_data* variables
+	 * store the information for the subdirectories so that we can do
+	 * that traversal order.
+	 */
+	struct traversal_callback_data *callback_data;
+	int callback_data_nr, callback_data_alloc;
+	char *callback_data_traverse_path;
+
+	/*
+	 * merge_trees: trees passed to the merge algorithm for the merge
+	 *
+	 * merge_trees records the trees passed to the merge algorithm.  But,
+	 * this data also is stored in merge_result->priv.  If a sequence of
+	 * merges are being done (such as when cherry-picking or rebasing),
+	 * the next merge can look at this and re-use information from
+	 * previous merges under certain circumstances.
+	 *
+	 * See also all the cached_* variables.
+	 */
+	struct tree *merge_trees[3];
+
+	/*
+	 * cached_pairs_valid_side: which side's cached info can be reused
+	 *
+	 * See the description for merge_trees.  For repeated merges, at most
+	 * only one side's cached information can be used.  Valid values:
+	 *   MERGE_SIDE2: cached data from side2 can be reused
+	 *   MERGE_SIDE1: cached data from side1 can be reused
+	 *   0:           no cached data can be reused
+	 *   -1:          See redo_after_renames; both sides can be reused.
+	 */
+	int cached_pairs_valid_side;
+
+	/*
+	 * cached_pairs: Caching of renames and deletions.
+	 *
+	 * These are mappings recording renames and deletions of individual
+	 * files (not directories).  They are thus a map from an old
+	 * filename to either NULL (for deletions) or a new filename (for
+	 * renames).
+	 */
+	struct strmap cached_pairs[3];
+
+	/*
+	 * cached_target_names: just the destinations from cached_pairs
+	 *
+	 * We sometimes want a fast lookup to determine if a given filename
+	 * is one of the destinations in cached_pairs.  cached_target_names
+	 * is thus duplicative information, but it provides a fast lookup.
+	 */
+	struct strset cached_target_names[3];
+
+	/*
+	 * cached_irrelevant: Caching of rename_sources that aren't relevant.
+	 *
+	 * If we try to detect a rename for a source path and succeed, it's
+	 * part of a rename.  If we try to detect a rename for a source path
+	 * and fail, then it's a delete.  If we do not try to detect a rename
+	 * for a path, then we don't know if it's a rename or a delete.  If
+	 * merge-ort doesn't think the path is relevant, then we just won't
+	 * cache anything for that path.  But there's a slight problem in
+	 * that merge-ort can think a path is RELEVANT_LOCATION, but due to
+	 * commit 9bd342137e ("diffcore-rename: determine which
+	 * relevant_sources are no longer relevant", 2021-03-13),
+	 * diffcore-rename can downgrade the path to RELEVANT_NO_MORE.  To
+	 * avoid excessive calls to diffcore_rename_extended() we still need
+	 * to cache such paths, though we cannot record them as either
+	 * renames or deletes.  So we cache them here as a "turned out to be
+	 * irrelevant *for this commit*" as they are often also irrelevant
+	 * for subsequent commits, though we will have to do some extra
+	 * checking to see whether such paths become relevant for rename
+	 * detection when cherry-picking/rebasing subsequent commits.
+	 */
+	struct strset cached_irrelevant[3];
+
+	/*
+	 * redo_after_renames: optimization flag for "restarting" the merge
+	 *
+	 * Sometimes it pays to detect renames, cache them, and then
+	 * restart the merge operation from the beginning.  The reason for
+	 * this is that when we know where all the renames are, we know
+	 * whether a certain directory has any paths under it affected --
+	 * and if a directory is not affected then it permits us to do
+	 * trivial tree merging in more cases.  Doing trivial tree merging
+	 * prevents the need to run process_entry() on every path
+	 * underneath trees that can be trivially merged, and
+	 * process_entry() is more expensive than collect_merge_info() --
+	 * plus, the second collect_merge_info() will be much faster since
+	 * it doesn't have to recurse into the relevant trees.
+	 *
+	 * Values for this flag:
+	 *   0 = don't bother, not worth it (or conditions not yet checked)
+	 *   1 = conditions for optimization met, optimization worthwhile
+	 *   2 = we already did it (don't restart merge yet again)
+	 */
+	unsigned redo_after_renames;
+
+	/*
+	 * needed_limit: value needed for inexact rename detection to run
+	 *
+	 * If the current rename limit wasn't high enough for inexact
+	 * rename detection to run, this records the limit needed.  Otherwise,
+	 * this value remains 0.
+	 */
+	int needed_limit;
+};
+
+struct merge_options_internal {
+	/*
+	 * paths: primary data structure in all of merge ort.
+	 *
+	 * The keys of paths:
+	 *   * are full relative paths from the toplevel of the repository
+	 *     (e.g. "drivers/firmware/raspberrypi.c").
+	 *   * store all relevant paths in the repo, both directories and
+	 *     files (e.g. drivers, drivers/firmware would also be included)
+	 *   * these keys serve to intern all the path strings, which allows
+	 *     us to do pointer comparison on directory names instead of
+	 *     strcmp; we just have to be careful to use the interned strings.
+	 *
+	 * The values of paths:
+	 *   * either a pointer to a merged_info, or a conflict_info struct
+	 *   * merged_info contains all relevant information for a
+	 *     non-conflicted entry.
+	 *   * conflict_info contains a merged_info, plus any additional
+	 *     information about a conflict such as the higher orders stages
+	 *     involved and the names of the paths those came from (handy
+	 *     once renames get involved).
+	 *   * a path may start "conflicted" (i.e. point to a conflict_info)
+	 *     and then a later step (e.g. three-way content merge) determines
+	 *     it can be cleanly merged, at which point it'll be marked clean
+	 *     and the algorithm will ignore any data outside the contained
+	 *     merged_info for that entry
+	 *   * If an entry remains conflicted, the merged_info portion of a
+	 *     conflict_info will later be filled with whatever version of
+	 *     the file should be placed in the working directory (e.g. an
+	 *     as-merged-as-possible variation that contains conflict markers).
+	 */
+	struct strmap paths;
+
+	/*
+	 * conflicted: a subset of keys->values from "paths"
+	 *
+	 * conflicted is basically an optimization between process_entries()
+	 * and record_conflicted_index_entries(); the latter could loop over
+	 * ALL the entries in paths AGAIN and look for the ones that are
+	 * still conflicted, but since process_entries() has to loop over
+	 * all of them, it saves the ones it couldn't resolve in this strmap
+	 * so that record_conflicted_index_entries() can iterate just the
+	 * relevant entries.
+	 */
+	struct strmap conflicted;
+
+	/*
+	 * pool: memory pool for fast allocation/deallocation
+	 *
+	 * We allocate room for lots of filenames and auxiliary data
+	 * structures in merge_options_internal, and it tends to all be
+	 * freed together too.  Using a memory pool for these provides a
+	 * nice speedup.
+	 */
+	struct mem_pool pool;
+
+	/*
+	 * conflicts: logical conflicts and messages stored by _primary_ path
+	 *
+	 * This is a map of pathnames (a subset of the keys in "paths" above)
+	 * to struct string_list, with each item's `util` containing a
+	 * `struct logical_conflict_info`. Note, though, that for each path,
+	 * it only stores the logical conflicts for which that path is the
+	 * primary path; the path might be part of additional conflicts.
+	 */
+	struct strmap conflicts;
+
+	/*
+	 * renames: various data relating to rename detection
+	 */
+	struct rename_info renames;
+
+	/*
+	 * attr_index: hacky minimal index used for renormalization
+	 *
+	 * renormalization code _requires_ an index, though it only needs to
+	 * find a .gitattributes file within the index.  So, when
+	 * renormalization is important, we create a special index with just
+	 * that one file.
+	 */
+	struct index_state attr_index;
+
+	/*
+	 * current_dir_name, toplevel_dir: temporary vars
+	 *
+	 * These are used in collect_merge_info_callback(), and will set the
+	 * various merged_info.directory_name for the various paths we get;
+	 * see documentation for that variable and the requirements placed on
+	 * that field.
+	 */
+	const char *current_dir_name;
+	const char *toplevel_dir;
+
+	/* call_depth: recursion level counter for merging merge bases */
+	int call_depth;
+
+	/* field that holds submodule conflict information */
+	struct string_list conflicted_submodules;
+};
+
+struct conflicted_submodule_item {
+	char *abbrev;
+	int flag;
+};
+
+static void conflicted_submodule_item_free(void *util, const char *str UNUSED)
+{
+	struct conflicted_submodule_item *item = util;
+
+	free(item->abbrev);
+	free(item);
+}
+
+struct version_info {
+	struct object_id oid;
+	unsigned short mode;
+};
+
+struct merged_info {
+	/* if is_null, ignore result.  otherwise result has oid & mode */
+	struct version_info result;
+	unsigned is_null:1;
+
+	/*
+	 * clean: whether the path in question is cleanly merged.
+	 *
+	 * see conflict_info.merged for more details.
+	 */
+	unsigned clean:1;
+
+	/*
+	 * basename_offset: offset of basename of path.
+	 *
+	 * perf optimization to avoid recomputing offset of final '/'
+	 * character in pathname (0 if no '/' in pathname).
+	 */
+	size_t basename_offset;
+
+	 /*
+	  * directory_name: containing directory name.
+	  *
+	  * Note that we assume directory_name is constructed such that
+	  *    strcmp(dir1_name, dir2_name) == 0 iff dir1_name == dir2_name,
+	  * i.e. string equality is equivalent to pointer equality.  For this
+	  * to hold, we have to be careful setting directory_name.
+	  */
+	const char *directory_name;
+};
+
+struct conflict_info {
+	/*
+	 * merged: the version of the path that will be written to working tree
+	 *
+	 * WARNING: It is critical to check merged.clean and ensure it is 0
+	 * before reading any conflict_info fields outside of merged.
+	 * Allocated merge_info structs will always have clean set to 1.
+	 * Allocated conflict_info structs will have merged.clean set to 0
+	 * initially.  The merged.clean field is how we know if it is safe
+	 * to access other parts of conflict_info besides merged; if a
+	 * conflict_info's merged.clean is changed to 1, the rest of the
+	 * algorithm is not allowed to look at anything outside of the
+	 * merged member anymore.
+	 */
+	struct merged_info merged;
+
+	/* oids & modes from each of the three trees for this path */
+	struct version_info stages[3];
+
+	/* pathnames for each stage; may differ due to rename detection */
+	const char *pathnames[3];
+
+	/* Whether this path is/was involved in a directory/file conflict */
+	unsigned df_conflict:1;
+
+	/*
+	 * Whether this path is/was involved in a non-content conflict other
+	 * than a directory/file conflict (e.g. rename/rename, rename/delete,
+	 * file location based on possible directory rename).
+	 */
+	unsigned path_conflict:1;
+
+	/*
+	 * For filemask and dirmask, the ith bit corresponds to whether the
+	 * ith entry is a file (filemask) or a directory (dirmask).  Thus,
+	 * filemask & dirmask is always zero, and filemask | dirmask is at
+	 * most 7 but can be less when a path does not appear as either a
+	 * file or a directory on at least one side of history.
+	 *
+	 * Note that these masks are related to enum merge_side, as the ith
+	 * entry corresponds to side i.
+	 *
+	 * These values come from a traverse_trees() call; more info may be
+	 * found looking at tree-walk.h's struct traverse_info,
+	 * particularly the documentation above the "fn" member (note that
+	 * filemask = mask & ~dirmask from that documentation).
+	 */
+	unsigned filemask:3;
+	unsigned dirmask:3;
+
+	/*
+	 * Optimization to track which stages match, to avoid the need to
+	 * recompute it in multiple steps. Either 0 or at least 2 bits are
+	 * set; if at least 2 bits are set, their corresponding stages match.
+	 */
+	unsigned match_mask:3;
+};
+
+enum conflict_and_info_types {
+	/* "Simple" conflicts and informational messages */
+	INFO_AUTO_MERGING = 0,
+	CONFLICT_CONTENTS,       /* text file that failed to merge */
+	CONFLICT_BINARY,
+	CONFLICT_FILE_DIRECTORY,
+	CONFLICT_DISTINCT_MODES,
+	CONFLICT_MODIFY_DELETE,
+
+	/* Regular rename */
+	CONFLICT_RENAME_RENAME,   /* same file renamed differently */
+	CONFLICT_RENAME_COLLIDES, /* rename/add or two files renamed to 1 */
+	CONFLICT_RENAME_DELETE,
+
+	/* Basic directory rename */
+	CONFLICT_DIR_RENAME_SUGGESTED,
+	INFO_DIR_RENAME_APPLIED,
+
+	/* Special directory rename cases */
+	INFO_DIR_RENAME_SKIPPED_DUE_TO_RERENAME,
+	CONFLICT_DIR_RENAME_FILE_IN_WAY,
+	CONFLICT_DIR_RENAME_COLLISION,
+	CONFLICT_DIR_RENAME_SPLIT,
+
+	/* Basic submodule */
+	INFO_SUBMODULE_FAST_FORWARDING,
+	CONFLICT_SUBMODULE_FAILED_TO_MERGE,
+
+	/* Special submodule cases broken out from FAILED_TO_MERGE */
+	CONFLICT_SUBMODULE_FAILED_TO_MERGE_BUT_POSSIBLE_RESOLUTION,
+	CONFLICT_SUBMODULE_NOT_INITIALIZED,
+	CONFLICT_SUBMODULE_HISTORY_NOT_AVAILABLE,
+	CONFLICT_SUBMODULE_MAY_HAVE_REWINDS,
+	CONFLICT_SUBMODULE_NULL_MERGE_BASE,
+
+	/* Keep this entry _last_ in the list */
+	NB_CONFLICT_TYPES,
+};
+
+/*
+ * Short description of conflict type, relied upon by external tools.
+ *
+ * We can add more entries, but DO NOT change any of these strings.  Also,
+ * Order MUST match conflict_info_and_types.
+ */
+static const char *type_short_descriptions[] = {
+	/*** "Simple" conflicts and informational messages ***/
+	[INFO_AUTO_MERGING] = "Auto-merging",
+	[CONFLICT_CONTENTS] = "CONFLICT (contents)",
+	[CONFLICT_BINARY] = "CONFLICT (binary)",
+	[CONFLICT_FILE_DIRECTORY] = "CONFLICT (file/directory)",
+	[CONFLICT_DISTINCT_MODES] = "CONFLICT (distinct modes)",
+	[CONFLICT_MODIFY_DELETE] = "CONFLICT (modify/delete)",
+
+	/*** Regular rename ***/
+	[CONFLICT_RENAME_RENAME] = "CONFLICT (rename/rename)",
+	[CONFLICT_RENAME_COLLIDES] = "CONFLICT (rename involved in collision)",
+	[CONFLICT_RENAME_DELETE] = "CONFLICT (rename/delete)",
+
+	/*** Basic directory rename ***/
+	[CONFLICT_DIR_RENAME_SUGGESTED] =
+		"CONFLICT (directory rename suggested)",
+	[INFO_DIR_RENAME_APPLIED] = "Path updated due to directory rename",
+
+	/*** Special directory rename cases ***/
+	[INFO_DIR_RENAME_SKIPPED_DUE_TO_RERENAME] =
+		"Directory rename skipped since directory was renamed on both sides",
+	[CONFLICT_DIR_RENAME_FILE_IN_WAY] =
+		"CONFLICT (file in way of directory rename)",
+	[CONFLICT_DIR_RENAME_COLLISION] = "CONFLICT(directory rename collision)",
+	[CONFLICT_DIR_RENAME_SPLIT] = "CONFLICT(directory rename unclear split)",
+
+	/*** Basic submodule ***/
+	[INFO_SUBMODULE_FAST_FORWARDING] = "Fast forwarding submodule",
+	[CONFLICT_SUBMODULE_FAILED_TO_MERGE] = "CONFLICT (submodule)",
+
+	/*** Special submodule cases broken out from FAILED_TO_MERGE ***/
+	[CONFLICT_SUBMODULE_FAILED_TO_MERGE_BUT_POSSIBLE_RESOLUTION] =
+		"CONFLICT (submodule with possible resolution)",
+	[CONFLICT_SUBMODULE_NOT_INITIALIZED] =
+		"CONFLICT (submodule not initialized)",
+	[CONFLICT_SUBMODULE_HISTORY_NOT_AVAILABLE] =
+		"CONFLICT (submodule history not available)",
+	[CONFLICT_SUBMODULE_MAY_HAVE_REWINDS] =
+		"CONFLICT (submodule may have rewinds)",
+	[CONFLICT_SUBMODULE_NULL_MERGE_BASE] =
+		"CONFLICT (submodule lacks merge base)"
+};
+
+struct logical_conflict_info {
+	enum conflict_and_info_types type;
+	struct strvec paths;
+};
+
+/*** Function Grouping: various utility functions ***/
+
+/*
+ * For the next three macros, see warning for conflict_info.merged.
+ *
+ * In each of the below, mi is a struct merged_info*, and ci was defined
+ * as a struct conflict_info* (but we need to verify ci isn't actually
+ * pointed at a struct merged_info*).
+ *
+ * INITIALIZE_CI: Assign ci to mi but only if it's safe; set to NULL otherwise.
+ * VERIFY_CI: Ensure that something we assigned to a conflict_info* is one.
+ * ASSIGN_AND_VERIFY_CI: Similar to VERIFY_CI but do assignment first.
+ */
+#define INITIALIZE_CI(ci, mi) do {                                           \
+	(ci) = (!(mi) || (mi)->clean) ? NULL : (struct conflict_info *)(mi); \
+} while (0)
+#define VERIFY_CI(ci) assert(ci && !ci->merged.clean);
+#define ASSIGN_AND_VERIFY_CI(ci, mi) do {    \
+	(ci) = (struct conflict_info *)(mi);  \
+	assert((ci) && !(mi)->clean);        \
+} while (0)
+
+static void free_strmap_strings(struct strmap *map)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+
+	strmap_for_each_entry(map, &iter, entry) {
+		free((char*)entry->key);
+	}
+}
+
+static void clear_or_reinit_internal_opts(struct merge_options_internal *opti,
+					  int reinitialize)
+{
+	struct rename_info *renames = &opti->renames;
+	int i;
+	void (*strmap_clear_func)(struct strmap *, int) =
+		reinitialize ? strmap_partial_clear : strmap_clear;
+	void (*strintmap_clear_func)(struct strintmap *) =
+		reinitialize ? strintmap_partial_clear : strintmap_clear;
+	void (*strset_clear_func)(struct strset *) =
+		reinitialize ? strset_partial_clear : strset_clear;
+
+	strmap_clear_func(&opti->paths, 0);
+
+	/*
+	 * All keys and values in opti->conflicted are a subset of those in
+	 * opti->paths.  We don't want to deallocate anything twice, so we
+	 * don't free the keys and we pass 0 for free_values.
+	 */
+	strmap_clear_func(&opti->conflicted, 0);
+
+	if (opti->attr_index.cache_nr) /* true iff opt->renormalize */
+		discard_index(&opti->attr_index);
+
+	/* Free memory used by various renames maps */
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; ++i) {
+		strintmap_clear_func(&renames->dirs_removed[i]);
+		strmap_clear_func(&renames->dir_renames[i], 0);
+		strintmap_clear_func(&renames->relevant_sources[i]);
+		if (!reinitialize)
+			assert(renames->cached_pairs_valid_side == 0);
+		if (i != renames->cached_pairs_valid_side &&
+		    -1 != renames->cached_pairs_valid_side) {
+			strset_clear_func(&renames->cached_target_names[i]);
+			strmap_clear_func(&renames->cached_pairs[i], 1);
+			strset_clear_func(&renames->cached_irrelevant[i]);
+			partial_clear_dir_rename_count(&renames->dir_rename_count[i]);
+			if (!reinitialize)
+				strmap_clear(&renames->dir_rename_count[i], 1);
+		}
+	}
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; ++i) {
+		strintmap_clear_func(&renames->deferred[i].possible_trivial_merges);
+		strset_clear_func(&renames->deferred[i].target_dirs);
+		renames->deferred[i].trivial_merges_okay = 1; /* 1 == maybe */
+	}
+	renames->cached_pairs_valid_side = 0;
+	renames->dir_rename_mask = 0;
+
+	if (!reinitialize) {
+		struct hashmap_iter iter;
+		struct strmap_entry *e;
+
+		/* Release and free each strbuf found in output */
+		strmap_for_each_entry(&opti->conflicts, &iter, e) {
+			struct string_list *list = e->value;
+			for (int i = 0; i < list->nr; i++) {
+				struct logical_conflict_info *info =
+					list->items[i].util;
+				strvec_clear(&info->paths);
+			}
+			/*
+			 * While strictly speaking we don't need to
+			 * free(conflicts) here because we could pass
+			 * free_values=1 when calling strmap_clear() on
+			 * opti->conflicts, that would require strmap_clear
+			 * to do another strmap_for_each_entry() loop, so we
+			 * just free it while we're iterating anyway.
+			 */
+			string_list_clear(list, 1);
+			free(list);
+		}
+		strmap_clear(&opti->conflicts, 0);
+	}
+
+	mem_pool_discard(&opti->pool, 0);
+
+	string_list_clear_func(&opti->conflicted_submodules,
+					conflicted_submodule_item_free);
+
+	/* Clean out callback_data as well. */
+	FREE_AND_NULL(renames->callback_data);
+	renames->callback_data_nr = renames->callback_data_alloc = 0;
+}
+
+__attribute__((format (printf, 2, 3)))
+static int err(struct merge_options *opt, const char *err, ...)
+{
+	va_list params;
+	struct strbuf sb = STRBUF_INIT;
+
+	strbuf_addstr(&sb, "error: ");
+	va_start(params, err);
+	strbuf_vaddf(&sb, err, params);
+	va_end(params);
+
+	error("%s", sb.buf);
+	strbuf_release(&sb);
+
+	return -1;
+}
+
+static void format_commit(struct strbuf *sb,
+			  int indent,
+			  struct repository *repo,
+			  struct commit *commit)
+{
+	struct merge_remote_desc *desc;
+	struct pretty_print_context ctx = {0};
+	ctx.abbrev = DEFAULT_ABBREV;
+
+	strbuf_addchars(sb, ' ', indent);
+	desc = merge_remote_util(commit);
+	if (desc) {
+		strbuf_addf(sb, "virtual %s\n", desc->name);
+		return;
+	}
+
+	repo_format_commit_message(repo, commit, "%h %s", sb, &ctx);
+	strbuf_addch(sb, '\n');
+}
+
+__attribute__((format (printf, 8, 9)))
+static void path_msg(struct merge_options *opt,
+		     enum conflict_and_info_types type,
+		     int omittable_hint, /* skippable under --remerge-diff */
+		     const char *primary_path,
+		     const char *other_path_1, /* may be NULL */
+		     const char *other_path_2, /* may be NULL */
+		     struct string_list *other_paths, /* may be NULL */
+		     const char *fmt, ...)
+{
+	va_list ap;
+	struct string_list *path_conflicts;
+	struct logical_conflict_info *info;
+	struct strbuf buf = STRBUF_INIT;
+	struct strbuf *dest;
+	struct strbuf tmp = STRBUF_INIT;
+
+	/* Sanity checks */
+	assert(omittable_hint ==
+	       !starts_with(type_short_descriptions[type], "CONFLICT") ||
+	       type == CONFLICT_DIR_RENAME_SUGGESTED);
+	if (opt->record_conflict_msgs_as_headers && omittable_hint)
+		return; /* Do not record mere hints in headers */
+	if (opt->priv->call_depth && opt->verbosity < 5)
+		return; /* Ignore messages from inner merges */
+
+	/* Ensure path_conflicts (ptr to array of logical_conflict) allocated */
+	path_conflicts = strmap_get(&opt->priv->conflicts, primary_path);
+	if (!path_conflicts) {
+		path_conflicts = xmalloc(sizeof(*path_conflicts));
+		string_list_init_dup(path_conflicts);
+		strmap_put(&opt->priv->conflicts, primary_path, path_conflicts);
+	}
+
+	/* Add a logical_conflict at the end to store info from this call */
+	info = xcalloc(1, sizeof(*info));
+	info->type = type;
+	strvec_init(&info->paths);
+
+	/* Handle the list of paths */
+	strvec_push(&info->paths, primary_path);
+	if (other_path_1)
+		strvec_push(&info->paths, other_path_1);
+	if (other_path_2)
+		strvec_push(&info->paths, other_path_2);
+	if (other_paths)
+		for (int i = 0; i < other_paths->nr; i++)
+		strvec_push(&info->paths, other_paths->items[i].string);
+
+	/* Handle message and its format, in normal case */
+	dest = (opt->record_conflict_msgs_as_headers ? &tmp : &buf);
+
+	va_start(ap, fmt);
+	if (opt->priv->call_depth) {
+		strbuf_addchars(dest, ' ', 2);
+		strbuf_addstr(dest, "From inner merge:");
+		strbuf_addchars(dest, ' ', opt->priv->call_depth * 2);
+	}
+	strbuf_vaddf(dest, fmt, ap);
+	va_end(ap);
+
+	/* Handle specialized formatting of message under --remerge-diff */
+	if (opt->record_conflict_msgs_as_headers) {
+		int i_sb = 0, i_tmp = 0;
+
+		/* Start with the specified prefix */
+		if (opt->msg_header_prefix)
+			strbuf_addf(&buf, "%s ", opt->msg_header_prefix);
+
+		/* Copy tmp to sb, adding spaces after newlines */
+		strbuf_grow(&buf, buf.len + 2*tmp.len); /* more than sufficient */
+		for (; i_tmp < tmp.len; i_tmp++, i_sb++) {
+			/* Copy next character from tmp to sb */
+			buf.buf[buf.len + i_sb] = tmp.buf[i_tmp];
+
+			/* If we copied a newline, add a space */
+			if (tmp.buf[i_tmp] == '\n')
+				buf.buf[++i_sb] = ' ';
+		}
+		/* Update length and ensure it's NUL-terminated */
+		buf.len += i_sb;
+		buf.buf[buf.len] = '\0';
+
+		strbuf_release(&tmp);
+	}
+	string_list_append_nodup(path_conflicts, strbuf_detach(&buf, NULL))
+		->util = info;
+}
+
+static struct diff_filespec *pool_alloc_filespec(struct mem_pool *pool,
+						 const char *path)
+{
+	/* Similar to alloc_filespec(), but allocate from pool and reuse path */
+	struct diff_filespec *spec;
+
+	spec = mem_pool_calloc(pool, 1, sizeof(*spec));
+	spec->path = (char*)path; /* spec won't modify it */
+
+	spec->count = 1;
+	spec->is_binary = -1;
+	return spec;
+}
+
+static struct diff_filepair *pool_diff_queue(struct mem_pool *pool,
+					     struct diff_queue_struct *queue,
+					     struct diff_filespec *one,
+					     struct diff_filespec *two)
+{
+	/* Same code as diff_queue(), except allocate from pool */
+	struct diff_filepair *dp;
+
+	dp = mem_pool_calloc(pool, 1, sizeof(*dp));
+	dp->one = one;
+	dp->two = two;
+	if (queue)
+		diff_q(queue, dp);
+	return dp;
+}
+
+/* add a string to a strbuf, but converting "/" to "_" */
+static void add_flattened_path(struct strbuf *out, const char *s)
+{
+	size_t i = out->len;
+	strbuf_addstr(out, s);
+	for (; i < out->len; i++)
+		if (out->buf[i] == '/')
+			out->buf[i] = '_';
+}
+
+static char *unique_path(struct merge_options *opt,
+			 const char *path,
+			 const char *branch)
+{
+	char *ret = NULL;
+	struct strbuf newpath = STRBUF_INIT;
+	int suffix = 0;
+	size_t base_len;
+	struct strmap *existing_paths = &opt->priv->paths;
+
+	strbuf_addf(&newpath, "%s~", path);
+	add_flattened_path(&newpath, branch);
+
+	base_len = newpath.len;
+	while (strmap_contains(existing_paths, newpath.buf)) {
+		strbuf_setlen(&newpath, base_len);
+		strbuf_addf(&newpath, "_%d", suffix++);
+	}
+
+	/* Track the new path in our memory pool */
+	ret = mem_pool_alloc(&opt->priv->pool, newpath.len + 1);
+	memcpy(ret, newpath.buf, newpath.len + 1);
+	strbuf_release(&newpath);
+	return ret;
+}
+
+/*** Function Grouping: functions related to collect_merge_info() ***/
+
+static int traverse_trees_wrapper_callback(int n,
+					   unsigned long mask,
+					   unsigned long dirmask,
+					   struct name_entry *names,
+					   struct traverse_info *info)
+{
+	struct merge_options *opt = info->data;
+	struct rename_info *renames = &opt->priv->renames;
+	unsigned filemask = mask & ~dirmask;
+
+	assert(n==3);
+
+	if (!renames->callback_data_traverse_path)
+		renames->callback_data_traverse_path = xstrdup(info->traverse_path);
+
+	if (filemask && filemask == renames->dir_rename_mask)
+		renames->dir_rename_mask = 0x07;
+
+	ALLOC_GROW(renames->callback_data, renames->callback_data_nr + 1,
+		   renames->callback_data_alloc);
+	renames->callback_data[renames->callback_data_nr].mask = mask;
+	renames->callback_data[renames->callback_data_nr].dirmask = dirmask;
+	COPY_ARRAY(renames->callback_data[renames->callback_data_nr].names,
+		   names, 3);
+	renames->callback_data_nr++;
+
+	return mask;
+}
+
+/*
+ * Much like traverse_trees(), BUT:
+ *   - read all the tree entries FIRST, saving them
+ *   - note that the above step provides an opportunity to compute necessary
+ *     additional details before the "real" traversal
+ *   - loop through the saved entries and call the original callback on them
+ */
+static int traverse_trees_wrapper(struct index_state *istate,
+				  int n,
+				  struct tree_desc *t,
+				  struct traverse_info *info)
+{
+	int ret, i, old_offset;
+	traverse_callback_t old_fn;
+	char *old_callback_data_traverse_path;
+	struct merge_options *opt = info->data;
+	struct rename_info *renames = &opt->priv->renames;
+
+	assert(renames->dir_rename_mask == 2 || renames->dir_rename_mask == 4);
+
+	old_callback_data_traverse_path = renames->callback_data_traverse_path;
+	old_fn = info->fn;
+	old_offset = renames->callback_data_nr;
+
+	renames->callback_data_traverse_path = NULL;
+	info->fn = traverse_trees_wrapper_callback;
+	ret = traverse_trees(istate, n, t, info);
+	if (ret < 0)
+		return ret;
+
+	info->traverse_path = renames->callback_data_traverse_path;
+	info->fn = old_fn;
+	for (i = old_offset; i < renames->callback_data_nr; ++i) {
+		info->fn(n,
+			 renames->callback_data[i].mask,
+			 renames->callback_data[i].dirmask,
+			 renames->callback_data[i].names,
+			 info);
+	}
+
+	renames->callback_data_nr = old_offset;
+	free(renames->callback_data_traverse_path);
+	renames->callback_data_traverse_path = old_callback_data_traverse_path;
+	info->traverse_path = NULL;
+	return 0;
+}
+
+static void setup_path_info(struct merge_options *opt,
+			    struct string_list_item *result,
+			    const char *current_dir_name,
+			    int current_dir_name_len,
+			    char *fullpath, /* we'll take over ownership */
+			    struct name_entry *names,
+			    struct name_entry *merged_version,
+			    unsigned is_null,     /* boolean */
+			    unsigned df_conflict, /* boolean */
+			    unsigned filemask,
+			    unsigned dirmask,
+			    int resolved          /* boolean */)
+{
+	/* result->util is void*, so mi is a convenience typed variable */
+	struct merged_info *mi;
+
+	assert(!is_null || resolved);
+	assert(!df_conflict || !resolved); /* df_conflict implies !resolved */
+	assert(resolved == (merged_version != NULL));
+
+	mi = mem_pool_calloc(&opt->priv->pool, 1,
+			     resolved ? sizeof(struct merged_info) :
+					sizeof(struct conflict_info));
+	mi->directory_name = current_dir_name;
+	mi->basename_offset = current_dir_name_len;
+	mi->clean = !!resolved;
+	if (resolved) {
+		mi->result.mode = merged_version->mode;
+		oidcpy(&mi->result.oid, &merged_version->oid);
+		mi->is_null = !!is_null;
+	} else {
+		int i;
+		struct conflict_info *ci;
+
+		ASSIGN_AND_VERIFY_CI(ci, mi);
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			ci->pathnames[i] = fullpath;
+			ci->stages[i].mode = names[i].mode;
+			oidcpy(&ci->stages[i].oid, &names[i].oid);
+		}
+		ci->filemask = filemask;
+		ci->dirmask = dirmask;
+		ci->df_conflict = !!df_conflict;
+		if (dirmask)
+			/*
+			 * Assume is_null for now, but if we have entries
+			 * under the directory then when it is complete in
+			 * write_completed_directory() it'll update this.
+			 * Also, for D/F conflicts, we have to handle the
+			 * directory first, then clear this bit and process
+			 * the file to see how it is handled -- that occurs
+			 * near the top of process_entry().
+			 */
+			mi->is_null = 1;
+	}
+	strmap_put(&opt->priv->paths, fullpath, mi);
+	result->string = fullpath;
+	result->util = mi;
+}
+
+static void add_pair(struct merge_options *opt,
+		     struct name_entry *names,
+		     const char *pathname,
+		     unsigned side,
+		     unsigned is_add /* if false, is_delete */,
+		     unsigned match_mask,
+		     unsigned dir_rename_mask)
+{
+	struct diff_filespec *one, *two;
+	struct rename_info *renames = &opt->priv->renames;
+	int names_idx = is_add ? side : 0;
+
+	if (is_add) {
+		assert(match_mask == 0 || match_mask == 6);
+		if (strset_contains(&renames->cached_target_names[side],
+				    pathname))
+			return;
+	} else {
+		unsigned content_relevant = (match_mask == 0);
+		unsigned location_relevant = (dir_rename_mask == 0x07);
+
+		assert(match_mask == 0 || match_mask == 3 || match_mask == 5);
+
+		/*
+		 * If pathname is found in cached_irrelevant[side] due to
+		 * previous pick but for this commit content is relevant,
+		 * then we need to remove it from cached_irrelevant.
+		 */
+		if (content_relevant)
+			/* strset_remove is no-op if strset doesn't have key */
+			strset_remove(&renames->cached_irrelevant[side],
+				      pathname);
+
+		/*
+		 * We do not need to re-detect renames for paths that we already
+		 * know the pairing, i.e. for cached_pairs (or
+		 * cached_irrelevant).  However, handle_deferred_entries() needs
+		 * to loop over the union of keys from relevant_sources[side] and
+		 * cached_pairs[side], so for simplicity we set relevant_sources
+		 * for all the cached_pairs too and then strip them back out in
+		 * prune_cached_from_relevant() at the beginning of
+		 * detect_regular_renames().
+		 */
+		if (content_relevant || location_relevant) {
+			/* content_relevant trumps location_relevant */
+			strintmap_set(&renames->relevant_sources[side], pathname,
+				      content_relevant ? RELEVANT_CONTENT : RELEVANT_LOCATION);
+		}
+
+		/*
+		 * Avoid creating pair if we've already cached rename results.
+		 * Note that we do this after setting relevant_sources[side]
+		 * as noted in the comment above.
+		 */
+		if (strmap_contains(&renames->cached_pairs[side], pathname) ||
+		    strset_contains(&renames->cached_irrelevant[side], pathname))
+			return;
+	}
+
+	one = pool_alloc_filespec(&opt->priv->pool, pathname);
+	two = pool_alloc_filespec(&opt->priv->pool, pathname);
+	fill_filespec(is_add ? two : one,
+		      &names[names_idx].oid, 1, names[names_idx].mode);
+	pool_diff_queue(&opt->priv->pool, &renames->pairs[side], one, two);
+}
+
+static void collect_rename_info(struct merge_options *opt,
+				struct name_entry *names,
+				const char *dirname,
+				const char *fullname,
+				unsigned filemask,
+				unsigned dirmask,
+				unsigned match_mask)
+{
+	struct rename_info *renames = &opt->priv->renames;
+	unsigned side;
+
+	/*
+	 * Update dir_rename_mask (determines ignore-rename-source validity)
+	 *
+	 * dir_rename_mask helps us keep track of when directory rename
+	 * detection may be relevant.  Basically, whenver a directory is
+	 * removed on one side of history, and a file is added to that
+	 * directory on the other side of history, directory rename
+	 * detection is relevant (meaning we have to detect renames for all
+	 * files within that directory to deduce where the directory
+	 * moved).  Also, whenever a directory needs directory rename
+	 * detection, due to the "majority rules" choice for where to move
+	 * it (see t6423 testcase 1f), we also need to detect renames for
+	 * all files within subdirectories of that directory as well.
+	 *
+	 * Here we haven't looked at files within the directory yet, we are
+	 * just looking at the directory itself.  So, if we aren't yet in
+	 * a case where a parent directory needed directory rename detection
+	 * (i.e. dir_rename_mask != 0x07), and if the directory was removed
+	 * on one side of history, record the mask of the other side of
+	 * history in dir_rename_mask.
+	 */
+	if (renames->dir_rename_mask != 0x07 &&
+	    (dirmask == 3 || dirmask == 5)) {
+		/* simple sanity check */
+		assert(renames->dir_rename_mask == 0 ||
+		       renames->dir_rename_mask == (dirmask & ~1));
+		/* update dir_rename_mask; have it record mask of new side */
+		renames->dir_rename_mask = (dirmask & ~1);
+	}
+
+	/* Update dirs_removed, as needed */
+	if (dirmask == 1 || dirmask == 3 || dirmask == 5) {
+		/* absent_mask = 0x07 - dirmask; sides = absent_mask/2 */
+		unsigned sides = (0x07 - dirmask)/2;
+		unsigned relevance = (renames->dir_rename_mask == 0x07) ?
+					RELEVANT_FOR_ANCESTOR : NOT_RELEVANT;
+		/*
+		 * Record relevance of this directory.  However, note that
+		 * when collect_merge_info_callback() recurses into this
+		 * directory and calls collect_rename_info() on paths
+		 * within that directory, if we find a path that was added
+		 * to this directory on the other side of history, we will
+		 * upgrade this value to RELEVANT_FOR_SELF; see below.
+		 */
+		if (sides & 1)
+			strintmap_set(&renames->dirs_removed[1], fullname,
+				      relevance);
+		if (sides & 2)
+			strintmap_set(&renames->dirs_removed[2], fullname,
+				      relevance);
+	}
+
+	/*
+	 * Here's the block that potentially upgrades to RELEVANT_FOR_SELF.
+	 * When we run across a file added to a directory.  In such a case,
+	 * find the directory of the file and upgrade its relevance.
+	 */
+	if (renames->dir_rename_mask == 0x07 &&
+	    (filemask == 2 || filemask == 4)) {
+		/*
+		 * Need directory rename for parent directory on other side
+		 * of history from added file.  Thus
+		 *    side = (~filemask & 0x06) >> 1
+		 * or
+		 *    side = 3 - (filemask/2).
+		 */
+		unsigned side = 3 - (filemask >> 1);
+		strintmap_set(&renames->dirs_removed[side], dirname,
+			      RELEVANT_FOR_SELF);
+	}
+
+	if (filemask == 0 || filemask == 7)
+		return;
+
+	for (side = MERGE_SIDE1; side <= MERGE_SIDE2; ++side) {
+		unsigned side_mask = (1 << side);
+
+		/* Check for deletion on side */
+		if ((filemask & 1) && !(filemask & side_mask))
+			add_pair(opt, names, fullname, side, 0 /* delete */,
+				 match_mask & filemask,
+				 renames->dir_rename_mask);
+
+		/* Check for addition on side */
+		if (!(filemask & 1) && (filemask & side_mask))
+			add_pair(opt, names, fullname, side, 1 /* add */,
+				 match_mask & filemask,
+				 renames->dir_rename_mask);
+	}
+}
+
+static int collect_merge_info_callback(int n,
+				       unsigned long mask,
+				       unsigned long dirmask,
+				       struct name_entry *names,
+				       struct traverse_info *info)
+{
+	/*
+	 * n is 3.  Always.
+	 * common ancestor (mbase) has mask 1, and stored in index 0 of names
+	 * head of side 1  (side1) has mask 2, and stored in index 1 of names
+	 * head of side 2  (side2) has mask 4, and stored in index 2 of names
+	 */
+	struct merge_options *opt = info->data;
+	struct merge_options_internal *opti = opt->priv;
+	struct rename_info *renames = &opt->priv->renames;
+	struct string_list_item pi;  /* Path Info */
+	struct conflict_info *ci; /* typed alias to pi.util (which is void*) */
+	struct name_entry *p;
+	size_t len;
+	char *fullpath;
+	const char *dirname = opti->current_dir_name;
+	unsigned prev_dir_rename_mask = renames->dir_rename_mask;
+	unsigned filemask = mask & ~dirmask;
+	unsigned match_mask = 0; /* will be updated below */
+	unsigned mbase_null = !(mask & 1);
+	unsigned side1_null = !(mask & 2);
+	unsigned side2_null = !(mask & 4);
+	unsigned side1_matches_mbase = (!side1_null && !mbase_null &&
+					names[0].mode == names[1].mode &&
+					oideq(&names[0].oid, &names[1].oid));
+	unsigned side2_matches_mbase = (!side2_null && !mbase_null &&
+					names[0].mode == names[2].mode &&
+					oideq(&names[0].oid, &names[2].oid));
+	unsigned sides_match = (!side1_null && !side2_null &&
+				names[1].mode == names[2].mode &&
+				oideq(&names[1].oid, &names[2].oid));
+
+	/*
+	 * Note: When a path is a file on one side of history and a directory
+	 * in another, we have a directory/file conflict.  In such cases, if
+	 * the conflict doesn't resolve from renames and deletions, then we
+	 * always leave directories where they are and move files out of the
+	 * way.  Thus, while struct conflict_info has a df_conflict field to
+	 * track such conflicts, we ignore that field for any directories at
+	 * a path and only pay attention to it for files at the given path.
+	 * The fact that we leave directories were they are also means that
+	 * we do not need to worry about getting additional df_conflict
+	 * information propagated from parent directories down to children
+	 * (unlike, say traverse_trees_recursive() in unpack-trees.c, which
+	 * sets a newinfo.df_conflicts field specifically to propagate it).
+	 */
+	unsigned df_conflict = (filemask != 0) && (dirmask != 0);
+
+	/* n = 3 is a fundamental assumption. */
+	if (n != 3)
+		BUG("Called collect_merge_info_callback wrong");
+
+	/*
+	 * A bunch of sanity checks verifying that traverse_trees() calls
+	 * us the way I expect.  Could just remove these at some point,
+	 * though maybe they are helpful to future code readers.
+	 */
+	assert(mbase_null == is_null_oid(&names[0].oid));
+	assert(side1_null == is_null_oid(&names[1].oid));
+	assert(side2_null == is_null_oid(&names[2].oid));
+	assert(!mbase_null || !side1_null || !side2_null);
+	assert(mask > 0 && mask < 8);
+
+	/* Determine match_mask */
+	if (side1_matches_mbase)
+		match_mask = (side2_matches_mbase ? 7 : 3);
+	else if (side2_matches_mbase)
+		match_mask = 5;
+	else if (sides_match)
+		match_mask = 6;
+
+	/*
+	 * Get the name of the relevant filepath, which we'll pass to
+	 * setup_path_info() for tracking.
+	 */
+	p = names;
+	while (!p->mode)
+		p++;
+	len = traverse_path_len(info, p->pathlen);
+
+	/* +1 in both of the following lines to include the NUL byte */
+	fullpath = mem_pool_alloc(&opt->priv->pool, len + 1);
+	make_traverse_path(fullpath, len + 1, info, p->path, p->pathlen);
+
+	/*
+	 * If mbase, side1, and side2 all match, we can resolve early.  Even
+	 * if these are trees, there will be no renames or anything
+	 * underneath.
+	 */
+	if (side1_matches_mbase && side2_matches_mbase) {
+		/* mbase, side1, & side2 all match; use mbase as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+0, mbase_null, 0 /* df_conflict */,
+				filemask, dirmask, 1 /* resolved */);
+		return mask;
+	}
+
+	/*
+	 * If the sides match, and all three paths are present and are
+	 * files, then we can take either as the resolution.  We can't do
+	 * this with trees, because there may be rename sources from the
+	 * merge_base.
+	 */
+	if (sides_match && filemask == 0x07) {
+		/* use side1 (== side2) version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+1, side1_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
+	/*
+	 * If side1 matches mbase and all three paths are present and are
+	 * files, then we can use side2 as the resolution.  We cannot
+	 * necessarily do so this for trees, because there may be rename
+	 * destinations within side2.
+	 */
+	if (side1_matches_mbase && filemask == 0x07) {
+		/* use side2 version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+2, side2_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
+	/* Similar to above but swapping sides 1 and 2 */
+	if (side2_matches_mbase && filemask == 0x07) {
+		/* use side1 version as resolution */
+		setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+				names, names+1, side1_null, 0,
+				filemask, dirmask, 1);
+		return mask;
+	}
+
+	/*
+	 * Sometimes we can tell that a source path need not be included in
+	 * rename detection -- namely, whenever either
+	 *    side1_matches_mbase && side2_null
+	 * or
+	 *    side2_matches_mbase && side1_null
+	 * However, we call collect_rename_info() even in those cases,
+	 * because exact renames are cheap and would let us remove both a
+	 * source and destination path.  We'll cull the unneeded sources
+	 * later.
+	 */
+	collect_rename_info(opt, names, dirname, fullpath,
+			    filemask, dirmask, match_mask);
+
+	/*
+	 * None of the special cases above matched, so we have a
+	 * provisional conflict.  (Rename detection might allow us to
+	 * unconflict some more cases, but that comes later so all we can
+	 * do now is record the different non-null file hashes.)
+	 */
+	setup_path_info(opt, &pi, dirname, info->pathlen, fullpath,
+			names, NULL, 0, df_conflict, filemask, dirmask, 0);
+
+	ci = pi.util;
+	VERIFY_CI(ci);
+	ci->match_mask = match_mask;
+
+	/* If dirmask, recurse into subdirectories */
+	if (dirmask) {
+		struct traverse_info newinfo;
+		struct tree_desc t[3];
+		void *buf[3] = {NULL, NULL, NULL};
+		const char *original_dir_name;
+		int i, ret, side;
+
+		/*
+		 * Check for whether we can avoid recursing due to one side
+		 * matching the merge base.  The side that does NOT match is
+		 * the one that might have a rename destination we need.
+		 */
+		assert(!side1_matches_mbase || !side2_matches_mbase);
+		side = side1_matches_mbase ? MERGE_SIDE2 :
+			side2_matches_mbase ? MERGE_SIDE1 : MERGE_BASE;
+		if (filemask == 0 && (dirmask == 2 || dirmask == 4)) {
+			/*
+			 * Also defer recursing into new directories; set up a
+			 * few variables to let us do so.
+			 */
+			ci->match_mask = (7 - dirmask);
+			side = dirmask / 2;
+		}
+		if (renames->dir_rename_mask != 0x07 &&
+		    side != MERGE_BASE &&
+		    renames->deferred[side].trivial_merges_okay &&
+		    !strset_contains(&renames->deferred[side].target_dirs,
+				     pi.string)) {
+			strintmap_set(&renames->deferred[side].possible_trivial_merges,
+				      pi.string, renames->dir_rename_mask);
+			renames->dir_rename_mask = prev_dir_rename_mask;
+			return mask;
+		}
+
+		/* We need to recurse */
+		ci->match_mask &= filemask;
+		newinfo = *info;
+		newinfo.prev = info;
+		newinfo.name = p->path;
+		newinfo.namelen = p->pathlen;
+		newinfo.pathlen = st_add3(newinfo.pathlen, p->pathlen, 1);
+		/*
+		 * If this directory we are about to recurse into cared about
+		 * its parent directory (the current directory) having a D/F
+		 * conflict, then we'd propagate the masks in this way:
+		 *    newinfo.df_conflicts |= (mask & ~dirmask);
+		 * But we don't worry about propagating D/F conflicts.  (See
+		 * comment near setting of local df_conflict variable near
+		 * the beginning of this function).
+		 */
+
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			if (i == 1 && side1_matches_mbase)
+				t[1] = t[0];
+			else if (i == 2 && side2_matches_mbase)
+				t[2] = t[0];
+			else if (i == 2 && sides_match)
+				t[2] = t[1];
+			else {
+				const struct object_id *oid = NULL;
+				if (dirmask & 1)
+					oid = &names[i].oid;
+				buf[i] = fill_tree_descriptor(opt->repo,
+							      t + i, oid);
+			}
+			dirmask >>= 1;
+		}
+
+		original_dir_name = opti->current_dir_name;
+		opti->current_dir_name = pi.string;
+		if (renames->dir_rename_mask == 0 ||
+		    renames->dir_rename_mask == 0x07)
+			ret = traverse_trees(NULL, 3, t, &newinfo);
+		else
+			ret = traverse_trees_wrapper(NULL, 3, t, &newinfo);
+		opti->current_dir_name = original_dir_name;
+		renames->dir_rename_mask = prev_dir_rename_mask;
+
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++)
+			free(buf[i]);
+
+		if (ret < 0)
+			return -1;
+	}
+
+	return mask;
+}
+
+static void resolve_trivial_directory_merge(struct conflict_info *ci, int side)
+{
+	VERIFY_CI(ci);
+	assert((side == 1 && ci->match_mask == 5) ||
+	       (side == 2 && ci->match_mask == 3));
+	oidcpy(&ci->merged.result.oid, &ci->stages[side].oid);
+	ci->merged.result.mode = ci->stages[side].mode;
+	ci->merged.is_null = is_null_oid(&ci->stages[side].oid);
+	ci->match_mask = 0;
+	ci->merged.clean = 1; /* (ci->filemask == 0); */
+}
+
+static int handle_deferred_entries(struct merge_options *opt,
+				   struct traverse_info *info)
+{
+	struct rename_info *renames = &opt->priv->renames;
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+	int side, ret = 0;
+	int path_count_before, path_count_after = 0;
+
+	path_count_before = strmap_get_size(&opt->priv->paths);
+	for (side = MERGE_SIDE1; side <= MERGE_SIDE2; side++) {
+		unsigned optimization_okay = 1;
+		struct strintmap copy;
+
+		/* Loop over the set of paths we need to know rename info for */
+		strset_for_each_entry(&renames->relevant_sources[side],
+				      &iter, entry) {
+			char *rename_target, *dir, *dir_marker;
+			struct strmap_entry *e;
+
+			/*
+			 * If we don't know delete/rename info for this path,
+			 * then we need to recurse into all trees to get all
+			 * adds to make sure we have it.
+			 */
+			if (strset_contains(&renames->cached_irrelevant[side],
+					    entry->key))
+				continue;
+			e = strmap_get_entry(&renames->cached_pairs[side],
+					     entry->key);
+			if (!e) {
+				optimization_okay = 0;
+				break;
+			}
+
+			/* If this is a delete, we have enough info already */
+			rename_target = e->value;
+			if (!rename_target)
+				continue;
+
+			/* If we already walked the rename target, we're good */
+			if (strmap_contains(&opt->priv->paths, rename_target))
+				continue;
+
+			/*
+			 * Otherwise, we need to get a list of directories that
+			 * will need to be recursed into to get this
+			 * rename_target.
+			 */
+			dir = xstrdup(rename_target);
+			while ((dir_marker = strrchr(dir, '/'))) {
+				*dir_marker = '\0';
+				if (strset_contains(&renames->deferred[side].target_dirs,
+						    dir))
+					break;
+				strset_add(&renames->deferred[side].target_dirs,
+					   dir);
+			}
+			free(dir);
+		}
+		renames->deferred[side].trivial_merges_okay = optimization_okay;
+		/*
+		 * We need to recurse into any directories in
+		 * possible_trivial_merges[side] found in target_dirs[side].
+		 * But when we recurse, we may need to queue up some of the
+		 * subdirectories for possible_trivial_merges[side].  Since
+		 * we can't safely iterate through a hashmap while also adding
+		 * entries, move the entries into 'copy', iterate over 'copy',
+		 * and then we'll also iterate anything added into
+		 * possible_trivial_merges[side] once this loop is done.
+		 */
+		copy = renames->deferred[side].possible_trivial_merges;
+		strintmap_init_with_options(&renames->deferred[side].possible_trivial_merges,
+					    0,
+					    &opt->priv->pool,
+					    0);
+		strintmap_for_each_entry(&copy, &iter, entry) {
+			const char *path = entry->key;
+			unsigned dir_rename_mask = (intptr_t)entry->value;
+			struct conflict_info *ci;
+			unsigned dirmask;
+			struct tree_desc t[3];
+			void *buf[3] = {NULL,};
+			int i;
+
+			ci = strmap_get(&opt->priv->paths, path);
+			VERIFY_CI(ci);
+			dirmask = ci->dirmask;
+
+			if (optimization_okay &&
+			    !strset_contains(&renames->deferred[side].target_dirs,
+					     path)) {
+				resolve_trivial_directory_merge(ci, side);
+				continue;
+			}
+
+			info->name = path;
+			info->namelen = strlen(path);
+			info->pathlen = info->namelen + 1;
+
+			for (i = 0; i < 3; i++, dirmask >>= 1) {
+				if (i == 1 && ci->match_mask == 3)
+					t[1] = t[0];
+				else if (i == 2 && ci->match_mask == 5)
+					t[2] = t[0];
+				else if (i == 2 && ci->match_mask == 6)
+					t[2] = t[1];
+				else {
+					const struct object_id *oid = NULL;
+					if (dirmask & 1)
+						oid = &ci->stages[i].oid;
+					buf[i] = fill_tree_descriptor(opt->repo,
+								      t+i, oid);
+				}
+			}
+
+			ci->match_mask &= ci->filemask;
+			opt->priv->current_dir_name = path;
+			renames->dir_rename_mask = dir_rename_mask;
+			if (renames->dir_rename_mask == 0 ||
+			    renames->dir_rename_mask == 0x07)
+				ret = traverse_trees(NULL, 3, t, info);
+			else
+				ret = traverse_trees_wrapper(NULL, 3, t, info);
+
+			for (i = MERGE_BASE; i <= MERGE_SIDE2; i++)
+				free(buf[i]);
+
+			if (ret < 0)
+				return ret;
+		}
+		strintmap_clear(&copy);
+		strintmap_for_each_entry(&renames->deferred[side].possible_trivial_merges,
+					 &iter, entry) {
+			const char *path = entry->key;
+			struct conflict_info *ci;
+
+			ci = strmap_get(&opt->priv->paths, path);
+			VERIFY_CI(ci);
+
+			assert(renames->deferred[side].trivial_merges_okay &&
+			       !strset_contains(&renames->deferred[side].target_dirs,
+						path));
+			resolve_trivial_directory_merge(ci, side);
+		}
+		if (!optimization_okay || path_count_after)
+			path_count_after = strmap_get_size(&opt->priv->paths);
+	}
+	if (path_count_after) {
+		/*
+		 * The choice of wanted_factor here does not affect
+		 * correctness, only performance.  When the
+		 *    path_count_after / path_count_before
+		 * ratio is high, redoing after renames is a big
+		 * performance boost.  I suspect that redoing is a wash
+		 * somewhere near a value of 2, and below that redoing will
+		 * slow things down.  I applied a fudge factor and picked
+		 * 3; see the commit message when this was introduced for
+		 * back of the envelope calculations for this ratio.
+		 */
+		const int wanted_factor = 3;
+
+		/* We should only redo collect_merge_info one time */
+		assert(renames->redo_after_renames == 0);
+
+		if (path_count_after / path_count_before >= wanted_factor) {
+			renames->redo_after_renames = 1;
+			renames->cached_pairs_valid_side = -1;
+		}
+	} else if (renames->redo_after_renames == 2)
+		renames->redo_after_renames = 0;
+	return ret;
+}
+
+static int collect_merge_info(struct merge_options *opt,
+			      struct tree *merge_base,
+			      struct tree *side1,
+			      struct tree *side2)
+{
+	int ret;
+	struct tree_desc t[3];
+	struct traverse_info info;
+
+	opt->priv->toplevel_dir = "";
+	opt->priv->current_dir_name = opt->priv->toplevel_dir;
+	setup_traverse_info(&info, opt->priv->toplevel_dir);
+	info.fn = collect_merge_info_callback;
+	info.data = opt;
+	info.show_all_errors = 1;
+
+	parse_tree(merge_base);
+	parse_tree(side1);
+	parse_tree(side2);
+	init_tree_desc(t + 0, merge_base->buffer, merge_base->size);
+	init_tree_desc(t + 1, side1->buffer, side1->size);
+	init_tree_desc(t + 2, side2->buffer, side2->size);
+
+	trace2_region_enter("merge", "traverse_trees", opt->repo);
+	ret = traverse_trees(NULL, 3, t, &info);
+	if (ret == 0)
+		ret = handle_deferred_entries(opt, &info);
+	trace2_region_leave("merge", "traverse_trees", opt->repo);
+
+	return ret;
+}
+
+/*** Function Grouping: functions related to threeway content merges ***/
+
+static int find_first_merges(struct repository *repo,
+			     const char *path,
+			     struct commit *a,
+			     struct commit *b,
+			     struct object_array *result)
+{
+	int i, j;
+	struct object_array merges = OBJECT_ARRAY_INIT;
+	struct commit *commit;
+	int contains_another;
+
+	char merged_revision[GIT_MAX_HEXSZ + 2];
+	const char *rev_args[] = { "rev-list", "--merges", "--ancestry-path",
+				   "--all", merged_revision, NULL };
+	struct rev_info revs;
+	struct setup_revision_opt rev_opts;
+
+	memset(result, 0, sizeof(struct object_array));
+	memset(&rev_opts, 0, sizeof(rev_opts));
+
+	/* get all revisions that merge commit a */
+	xsnprintf(merged_revision, sizeof(merged_revision), "^%s",
+		  oid_to_hex(&a->object.oid));
+	repo_init_revisions(repo, &revs, NULL);
+	/* FIXME: can't handle linked worktrees in submodules yet */
+	revs.single_worktree = path != NULL;
+	setup_revisions(ARRAY_SIZE(rev_args)-1, rev_args, &revs, &rev_opts);
+
+	/* save all revisions from the above list that contain b */
+	if (prepare_revision_walk(&revs))
+		die("revision walk setup failed");
+	while ((commit = get_revision(&revs)) != NULL) {
+		struct object *o = &(commit->object);
+		if (repo_in_merge_bases(repo, b, commit))
+			add_object_array(o, NULL, &merges);
+	}
+	reset_revision_walk();
+
+	/* Now we've got all merges that contain a and b. Prune all
+	 * merges that contain another found merge and save them in
+	 * result.
+	 */
+	for (i = 0; i < merges.nr; i++) {
+		struct commit *m1 = (struct commit *) merges.objects[i].item;
+
+		contains_another = 0;
+		for (j = 0; j < merges.nr; j++) {
+			struct commit *m2 = (struct commit *) merges.objects[j].item;
+			if (i != j && repo_in_merge_bases(repo, m2, m1)) {
+				contains_another = 1;
+				break;
+			}
+		}
+
+		if (!contains_another)
+			add_object_array(merges.objects[i].item, NULL, result);
+	}
+
+	object_array_clear(&merges);
+	release_revisions(&revs);
+	return result->nr;
+}
+
+static int merge_submodule(struct merge_options *opt,
+			   const char *path,
+			   const struct object_id *o,
+			   const struct object_id *a,
+			   const struct object_id *b,
+			   struct object_id *result)
+{
+	struct repository subrepo;
+	struct strbuf sb = STRBUF_INIT;
+	int ret = 0;
+	struct commit *commit_o, *commit_a, *commit_b;
+	int parent_count;
+	struct object_array merges;
+
+	int i;
+	int search = !opt->priv->call_depth;
+	int sub_not_initialized = 1;
+	int sub_flag = CONFLICT_SUBMODULE_FAILED_TO_MERGE;
+
+	/* store fallback answer in result in case we fail */
+	oidcpy(result, opt->priv->call_depth ? o : a);
+
+	/* we can not handle deletion conflicts */
+	if (is_null_oid(a) || is_null_oid(b))
+		BUG("submodule deleted on one side; this should be handled outside of merge_submodule()");
+
+	if ((sub_not_initialized = repo_submodule_init(&subrepo,
+		opt->repo, path, null_oid()))) {
+		path_msg(opt, CONFLICT_SUBMODULE_NOT_INITIALIZED, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s (not checked out)"),
+			 path);
+		sub_flag = CONFLICT_SUBMODULE_NOT_INITIALIZED;
+		goto cleanup;
+	}
+
+	if (is_null_oid(o)) {
+		path_msg(opt, CONFLICT_SUBMODULE_NULL_MERGE_BASE, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s (no merge base)"),
+			 path);
+		goto cleanup;
+	}
+
+	if (!(commit_o = lookup_commit_reference(&subrepo, o)) ||
+	    !(commit_a = lookup_commit_reference(&subrepo, a)) ||
+	    !(commit_b = lookup_commit_reference(&subrepo, b))) {
+		path_msg(opt, CONFLICT_SUBMODULE_HISTORY_NOT_AVAILABLE, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s (commits not present)"),
+			 path);
+		sub_flag = CONFLICT_SUBMODULE_HISTORY_NOT_AVAILABLE;
+		goto cleanup;
+	}
+
+	/* check whether both changes are forward */
+	if (!repo_in_merge_bases(&subrepo, commit_o, commit_a) ||
+	    !repo_in_merge_bases(&subrepo, commit_o, commit_b)) {
+		path_msg(opt, CONFLICT_SUBMODULE_MAY_HAVE_REWINDS, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s "
+			   "(commits don't follow merge-base)"),
+			 path);
+		goto cleanup;
+	}
+
+	/* Case #1: a is contained in b or vice versa */
+	if (repo_in_merge_bases(&subrepo, commit_a, commit_b)) {
+		oidcpy(result, b);
+		path_msg(opt, INFO_SUBMODULE_FAST_FORWARDING, 1,
+			 path, NULL, NULL, NULL,
+			 _("Note: Fast-forwarding submodule %s to %s"),
+			 path, oid_to_hex(b));
+		ret = 1;
+		goto cleanup;
+	}
+	if (repo_in_merge_bases(&subrepo, commit_b, commit_a)) {
+		oidcpy(result, a);
+		path_msg(opt, INFO_SUBMODULE_FAST_FORWARDING, 1,
+			 path, NULL, NULL, NULL,
+			 _("Note: Fast-forwarding submodule %s to %s"),
+			 path, oid_to_hex(a));
+		ret = 1;
+		goto cleanup;
+	}
+
+	/*
+	 * Case #2: There are one or more merges that contain a and b in
+	 * the submodule. If there is only one, then present it as a
+	 * suggestion to the user, but leave it marked unmerged so the
+	 * user needs to confirm the resolution.
+	 */
+
+	/* Skip the search if makes no sense to the calling context.  */
+	if (!search)
+		goto cleanup;
+
+	/* find commit which merges them */
+	parent_count = find_first_merges(&subrepo, path, commit_a, commit_b,
+					 &merges);
+	switch (parent_count) {
+	case 0:
+		path_msg(opt, CONFLICT_SUBMODULE_FAILED_TO_MERGE, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s"), path);
+		break;
+
+	case 1:
+		format_commit(&sb, 4, &subrepo,
+			      (struct commit *)merges.objects[0].item);
+		path_msg(opt, CONFLICT_SUBMODULE_FAILED_TO_MERGE_BUT_POSSIBLE_RESOLUTION, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s, but a possible merge "
+			   "resolution exists: %s"),
+			 path, sb.buf);
+		strbuf_release(&sb);
+		break;
+	default:
+		for (i = 0; i < merges.nr; i++)
+			format_commit(&sb, 4, &subrepo,
+				      (struct commit *)merges.objects[i].item);
+		path_msg(opt, CONFLICT_SUBMODULE_FAILED_TO_MERGE_BUT_POSSIBLE_RESOLUTION, 0,
+			 path, NULL, NULL, NULL,
+			 _("Failed to merge submodule %s, but multiple "
+			   "possible merges exist:\n%s"), path, sb.buf);
+		strbuf_release(&sb);
+	}
+
+	object_array_clear(&merges);
+cleanup:
+	if (!opt->priv->call_depth && !ret) {
+		struct string_list *csub = &opt->priv->conflicted_submodules;
+		struct conflicted_submodule_item *util;
+		const char *abbrev;
+
+		util = xmalloc(sizeof(*util));
+		util->flag = sub_flag;
+		util->abbrev = NULL;
+		if (!sub_not_initialized) {
+			abbrev = repo_find_unique_abbrev(&subrepo, b, DEFAULT_ABBREV);
+			util->abbrev = xstrdup(abbrev);
+		}
+		string_list_append(csub, path)->util = util;
+	}
+
+	if (!sub_not_initialized)
+		repo_clear(&subrepo);
+	return ret;
+}
+
+static void initialize_attr_index(struct merge_options *opt)
+{
+	/*
+	 * The renormalize_buffer() functions require attributes, and
+	 * annoyingly those can only be read from the working tree or from
+	 * an index_state.  merge-ort doesn't have an index_state, so we
+	 * generate a fake one containing only attribute information.
+	 */
+	struct merged_info *mi;
+	struct index_state *attr_index = &opt->priv->attr_index;
+	struct cache_entry *ce;
+
+	attr_index->initialized = 1;
+
+	if (!opt->renormalize)
+		return;
+
+	mi = strmap_get(&opt->priv->paths, GITATTRIBUTES_FILE);
+	if (!mi)
+		return;
+
+	if (mi->clean) {
+		int len = strlen(GITATTRIBUTES_FILE);
+		ce = make_empty_cache_entry(attr_index, len);
+		ce->ce_mode = create_ce_mode(mi->result.mode);
+		ce->ce_flags = create_ce_flags(0);
+		ce->ce_namelen = len;
+		oidcpy(&ce->oid, &mi->result.oid);
+		memcpy(ce->name, GITATTRIBUTES_FILE, len);
+		add_index_entry(attr_index, ce,
+				ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
+		get_stream_filter(attr_index, GITATTRIBUTES_FILE, &ce->oid);
+	} else {
+		int stage, len;
+		struct conflict_info *ci;
+
+		ASSIGN_AND_VERIFY_CI(ci, mi);
+		for (stage = 0; stage < 3; stage++) {
+			unsigned stage_mask = (1 << stage);
+
+			if (!(ci->filemask & stage_mask))
+				continue;
+			len = strlen(GITATTRIBUTES_FILE);
+			ce = make_empty_cache_entry(attr_index, len);
+			ce->ce_mode = create_ce_mode(ci->stages[stage].mode);
+			ce->ce_flags = create_ce_flags(stage);
+			ce->ce_namelen = len;
+			oidcpy(&ce->oid, &ci->stages[stage].oid);
+			memcpy(ce->name, GITATTRIBUTES_FILE, len);
+			add_index_entry(attr_index, ce,
+					ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
+			get_stream_filter(attr_index, GITATTRIBUTES_FILE,
+					  &ce->oid);
+		}
+	}
+}
+
+static int merge_3way(struct merge_options *opt,
+		      const char *path,
+		      const struct object_id *o,
+		      const struct object_id *a,
+		      const struct object_id *b,
+		      const char *pathnames[3],
+		      const int extra_marker_size,
+		      mmbuffer_t *result_buf)
+{
+	mmfile_t orig, src1, src2;
+	struct ll_merge_options ll_opts = {0};
+	char *base, *name1, *name2;
+	enum ll_merge_result merge_status;
+
+	if (!opt->priv->attr_index.initialized)
+		initialize_attr_index(opt);
+
+	ll_opts.renormalize = opt->renormalize;
+	ll_opts.extra_marker_size = extra_marker_size;
+	ll_opts.xdl_opts = opt->xdl_opts;
+
+	if (opt->priv->call_depth) {
+		ll_opts.virtual_ancestor = 1;
+		ll_opts.variant = 0;
+	} else {
+		switch (opt->recursive_variant) {
+		case MERGE_VARIANT_OURS:
+			ll_opts.variant = XDL_MERGE_FAVOR_OURS;
+			break;
+		case MERGE_VARIANT_THEIRS:
+			ll_opts.variant = XDL_MERGE_FAVOR_THEIRS;
+			break;
+		default:
+			ll_opts.variant = 0;
+			break;
+		}
+	}
+
+	assert(pathnames[0] && pathnames[1] && pathnames[2] && opt->ancestor);
+	if (pathnames[0] == pathnames[1] && pathnames[1] == pathnames[2]) {
+		base  = mkpathdup("%s", opt->ancestor);
+		name1 = mkpathdup("%s", opt->branch1);
+		name2 = mkpathdup("%s", opt->branch2);
+	} else {
+		base  = mkpathdup("%s:%s", opt->ancestor, pathnames[0]);
+		name1 = mkpathdup("%s:%s", opt->branch1,  pathnames[1]);
+		name2 = mkpathdup("%s:%s", opt->branch2,  pathnames[2]);
+	}
+
+	read_mmblob(&orig, o);
+	read_mmblob(&src1, a);
+	read_mmblob(&src2, b);
+
+	merge_status = ll_merge(result_buf, path, &orig, base,
+				&src1, name1, &src2, name2,
+				&opt->priv->attr_index, &ll_opts);
+	if (merge_status == LL_MERGE_BINARY_CONFLICT)
+		path_msg(opt, CONFLICT_BINARY, 0,
+			 path, NULL, NULL, NULL,
+			 "warning: Cannot merge binary files: %s (%s vs. %s)",
+			 path, name1, name2);
+
+	free(base);
+	free(name1);
+	free(name2);
+	free(orig.ptr);
+	free(src1.ptr);
+	free(src2.ptr);
+	return merge_status;
+}
+
+static int handle_content_merge(struct merge_options *opt,
+				const char *path,
+				const struct version_info *o,
+				const struct version_info *a,
+				const struct version_info *b,
+				const char *pathnames[3],
+				const int extra_marker_size,
+				struct version_info *result)
+{
+	/*
+	 * path is the target location where we want to put the file, and
+	 * is used to determine any normalization rules in ll_merge.
+	 *
+	 * The normal case is that path and all entries in pathnames are
+	 * identical, though renames can affect which path we got one of
+	 * the three blobs to merge on various sides of history.
+	 *
+	 * extra_marker_size is the amount to extend conflict markers in
+	 * ll_merge; this is neeed if we have content merges of content
+	 * merges, which happens for example with rename/rename(2to1) and
+	 * rename/add conflicts.
+	 */
+	unsigned clean = 1;
+
+	/*
+	 * handle_content_merge() needs both files to be of the same type, i.e.
+	 * both files OR both submodules OR both symlinks.  Conflicting types
+	 * needs to be handled elsewhere.
+	 */
+	assert((S_IFMT & a->mode) == (S_IFMT & b->mode));
+
+	/* Merge modes */
+	if (a->mode == b->mode || a->mode == o->mode)
+		result->mode = b->mode;
+	else {
+		/* must be the 100644/100755 case */
+		assert(S_ISREG(a->mode));
+		result->mode = a->mode;
+		clean = (b->mode == o->mode);
+		/*
+		 * FIXME: If opt->priv->call_depth && !clean, then we really
+		 * should not make result->mode match either a->mode or
+		 * b->mode; that causes t6036 "check conflicting mode for
+		 * regular file" to fail.  It would be best to use some other
+		 * mode, but we'll confuse all kinds of stuff if we use one
+		 * where S_ISREG(result->mode) isn't true, and if we use
+		 * something like 0100666, then tree-walk.c's calls to
+		 * canon_mode() will just normalize that to 100644 for us and
+		 * thus not solve anything.
+		 *
+		 * Figure out if there's some kind of way we can work around
+		 * this...
+		 */
+	}
+
+	/*
+	 * Trivial oid merge.
+	 *
+	 * Note: While one might assume that the next four lines would
+	 * be unnecessary due to the fact that match_mask is often
+	 * setup and already handled, renames don't always take care
+	 * of that.
+	 */
+	if (oideq(&a->oid, &b->oid) || oideq(&a->oid, &o->oid))
+		oidcpy(&result->oid, &b->oid);
+	else if (oideq(&b->oid, &o->oid))
+		oidcpy(&result->oid, &a->oid);
+
+	/* Remaining rules depend on file vs. submodule vs. symlink. */
+	else if (S_ISREG(a->mode)) {
+		mmbuffer_t result_buf;
+		int ret = 0, merge_status;
+		int two_way;
+
+		/*
+		 * If 'o' is different type, treat it as null so we do a
+		 * two-way merge.
+		 */
+		two_way = ((S_IFMT & o->mode) != (S_IFMT & a->mode));
+
+		merge_status = merge_3way(opt, path,
+					  two_way ? null_oid() : &o->oid,
+					  &a->oid, &b->oid,
+					  pathnames, extra_marker_size,
+					  &result_buf);
+
+		if ((merge_status < 0) || !result_buf.ptr)
+			ret = err(opt, _("Failed to execute internal merge"));
+
+		if (!ret &&
+		    write_object_file(result_buf.ptr, result_buf.size,
+				      OBJ_BLOB, &result->oid))
+			ret = err(opt, _("Unable to add %s to database"),
+				  path);
+
+		free(result_buf.ptr);
+		if (ret)
+			return -1;
+		clean &= (merge_status == 0);
+		path_msg(opt, INFO_AUTO_MERGING, 1, path, NULL, NULL, NULL,
+			 _("Auto-merging %s"), path);
+	} else if (S_ISGITLINK(a->mode)) {
+		int two_way = ((S_IFMT & o->mode) != (S_IFMT & a->mode));
+		clean = merge_submodule(opt, pathnames[0],
+					two_way ? null_oid() : &o->oid,
+					&a->oid, &b->oid, &result->oid);
+		if (opt->priv->call_depth && two_way && !clean) {
+			result->mode = o->mode;
+			oidcpy(&result->oid, &o->oid);
+		}
+	} else if (S_ISLNK(a->mode)) {
+		if (opt->priv->call_depth) {
+			clean = 0;
+			result->mode = o->mode;
+			oidcpy(&result->oid, &o->oid);
+		} else {
+			switch (opt->recursive_variant) {
+			case MERGE_VARIANT_NORMAL:
+				clean = 0;
+				oidcpy(&result->oid, &a->oid);
+				break;
+			case MERGE_VARIANT_OURS:
+				oidcpy(&result->oid, &a->oid);
+				break;
+			case MERGE_VARIANT_THEIRS:
+				oidcpy(&result->oid, &b->oid);
+				break;
+			}
+		}
+	} else
+		BUG("unsupported object type in the tree: %06o for %s",
+		    a->mode, path);
+
+	return clean;
+}
+
+/*** Function Grouping: functions related to detect_and_process_renames(), ***
+ *** which are split into directory and regular rename detection sections. ***/
+
+/*** Function Grouping: functions related to directory rename detection ***/
+
+struct collision_info {
+	struct string_list source_files;
+	unsigned reported_already:1;
+};
+
+/*
+ * Return a new string that replaces the beginning portion (which matches
+ * rename_info->key), with rename_info->util.new_dir.  In perl-speak:
+ *   new_path_name = (old_path =~ s/rename_info->key/rename_info->value/);
+ * NOTE:
+ *   Caller must ensure that old_path starts with rename_info->key + '/'.
+ */
+static char *apply_dir_rename(struct strmap_entry *rename_info,
+			      const char *old_path)
+{
+	struct strbuf new_path = STRBUF_INIT;
+	const char *old_dir = rename_info->key;
+	const char *new_dir = rename_info->value;
+	int oldlen, newlen, new_dir_len;
+
+	oldlen = strlen(old_dir);
+	if (*new_dir == '\0')
+		/*
+		 * If someone renamed/merged a subdirectory into the root
+		 * directory (e.g. 'some/subdir' -> ''), then we want to
+		 * avoid returning
+		 *     '' + '/filename'
+		 * as the rename; we need to make old_path + oldlen advance
+		 * past the '/' character.
+		 */
+		oldlen++;
+	new_dir_len = strlen(new_dir);
+	newlen = new_dir_len + (strlen(old_path) - oldlen) + 1;
+	strbuf_grow(&new_path, newlen);
+	strbuf_add(&new_path, new_dir, new_dir_len);
+	strbuf_addstr(&new_path, &old_path[oldlen]);
+
+	return strbuf_detach(&new_path, NULL);
+}
+
+static int path_in_way(struct strmap *paths, const char *path, unsigned side_mask)
+{
+	struct merged_info *mi = strmap_get(paths, path);
+	struct conflict_info *ci;
+	if (!mi)
+		return 0;
+	INITIALIZE_CI(ci, mi);
+	return mi->clean || (side_mask & (ci->filemask | ci->dirmask));
+}
+
+/*
+ * See if there is a directory rename for path, and if there are any file
+ * level conflicts on the given side for the renamed location.  If there is
+ * a rename and there are no conflicts, return the new name.  Otherwise,
+ * return NULL.
+ */
+static char *handle_path_level_conflicts(struct merge_options *opt,
+					 const char *path,
+					 unsigned side_index,
+					 struct strmap_entry *rename_info,
+					 struct strmap *collisions)
+{
+	char *new_path = NULL;
+	struct collision_info *c_info;
+	int clean = 1;
+	struct strbuf collision_paths = STRBUF_INIT;
+
+	/*
+	 * entry has the mapping of old directory name to new directory name
+	 * that we want to apply to path.
+	 */
+	new_path = apply_dir_rename(rename_info, path);
+	if (!new_path)
+		BUG("Failed to apply directory rename!");
+
+	/*
+	 * The caller needs to have ensured that it has pre-populated
+	 * collisions with all paths that map to new_path.  Do a quick check
+	 * to ensure that's the case.
+	 */
+	c_info = strmap_get(collisions, new_path);
+	if (!c_info)
+		BUG("c_info is NULL");
+
+	/*
+	 * Check for one-sided add/add/.../add conflicts, i.e.
+	 * where implicit renames from the other side doing
+	 * directory rename(s) can affect this side of history
+	 * to put multiple paths into the same location.  Warn
+	 * and bail on directory renames for such paths.
+	 */
+	if (c_info->reported_already) {
+		clean = 0;
+	} else if (path_in_way(&opt->priv->paths, new_path, 1 << side_index)) {
+		c_info->reported_already = 1;
+		strbuf_add_separated_string_list(&collision_paths, ", ",
+						 &c_info->source_files);
+		path_msg(opt, CONFLICT_DIR_RENAME_FILE_IN_WAY, 0,
+			 new_path, NULL, NULL, &c_info->source_files,
+			 _("CONFLICT (implicit dir rename): Existing "
+			   "file/dir at %s in the way of implicit "
+			   "directory rename(s) putting the following "
+			   "path(s) there: %s."),
+			 new_path, collision_paths.buf);
+		clean = 0;
+	} else if (c_info->source_files.nr > 1) {
+		c_info->reported_already = 1;
+		strbuf_add_separated_string_list(&collision_paths, ", ",
+						 &c_info->source_files);
+		path_msg(opt, CONFLICT_DIR_RENAME_COLLISION, 0,
+			 new_path, NULL, NULL, &c_info->source_files,
+			 _("CONFLICT (implicit dir rename): Cannot map "
+			   "more than one path to %s; implicit directory "
+			   "renames tried to put these paths there: %s"),
+			 new_path, collision_paths.buf);
+		clean = 0;
+	}
+
+	/* Free memory we no longer need */
+	strbuf_release(&collision_paths);
+	if (!clean && new_path) {
+		free(new_path);
+		return NULL;
+	}
+
+	return new_path;
+}
+
+static void get_provisional_directory_renames(struct merge_options *opt,
+					      unsigned side,
+					      int *clean)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+	struct rename_info *renames = &opt->priv->renames;
+
+	/*
+	 * Collapse
+	 *    dir_rename_count: old_directory -> {new_directory -> count}
+	 * down to
+	 *    dir_renames: old_directory -> best_new_directory
+	 * where best_new_directory is the one with the unique highest count.
+	 */
+	strmap_for_each_entry(&renames->dir_rename_count[side], &iter, entry) {
+		const char *source_dir = entry->key;
+		struct strintmap *counts = entry->value;
+		struct hashmap_iter count_iter;
+		struct strmap_entry *count_entry;
+		int max = 0;
+		int bad_max = 0;
+		const char *best = NULL;
+
+		strintmap_for_each_entry(counts, &count_iter, count_entry) {
+			const char *target_dir = count_entry->key;
+			intptr_t count = (intptr_t)count_entry->value;
+
+			if (count == max)
+				bad_max = max;
+			else if (count > max) {
+				max = count;
+				best = target_dir;
+			}
+		}
+
+		if (max == 0)
+			continue;
+
+		if (bad_max == max) {
+			path_msg(opt, CONFLICT_DIR_RENAME_SPLIT, 0,
+				 source_dir, NULL, NULL, NULL,
+				 _("CONFLICT (directory rename split): "
+				   "Unclear where to rename %s to; it was "
+				   "renamed to multiple other directories, "
+				   "with no destination getting a majority of "
+				   "the files."),
+				 source_dir);
+			*clean = 0;
+		} else {
+			strmap_put(&renames->dir_renames[side],
+				   source_dir, (void*)best);
+		}
+	}
+}
+
+static void handle_directory_level_conflicts(struct merge_options *opt)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+	struct string_list duplicated = STRING_LIST_INIT_NODUP;
+	struct rename_info *renames = &opt->priv->renames;
+	struct strmap *side1_dir_renames = &renames->dir_renames[MERGE_SIDE1];
+	struct strmap *side2_dir_renames = &renames->dir_renames[MERGE_SIDE2];
+	int i;
+
+	strmap_for_each_entry(side1_dir_renames, &iter, entry) {
+		if (strmap_contains(side2_dir_renames, entry->key))
+			string_list_append(&duplicated, entry->key);
+	}
+
+	for (i = 0; i < duplicated.nr; i++) {
+		strmap_remove(side1_dir_renames, duplicated.items[i].string, 0);
+		strmap_remove(side2_dir_renames, duplicated.items[i].string, 0);
+	}
+	string_list_clear(&duplicated, 0);
+}
+
+static struct strmap_entry *check_dir_renamed(const char *path,
+					      struct strmap *dir_renames)
+{
+	char *temp = xstrdup(path);
+	char *end;
+	struct strmap_entry *e = NULL;
+
+	while ((end = strrchr(temp, '/'))) {
+		*end = '\0';
+		e = strmap_get_entry(dir_renames, temp);
+		if (e)
+			break;
+	}
+	free(temp);
+	return e;
+}
+
+static void compute_collisions(struct strmap *collisions,
+			       struct strmap *dir_renames,
+			       struct diff_queue_struct *pairs)
+{
+	int i;
+
+	strmap_init_with_options(collisions, NULL, 0);
+	if (strmap_empty(dir_renames))
+		return;
+
+	/*
+	 * Multiple files can be mapped to the same path due to directory
+	 * renames done by the other side of history.  Since that other
+	 * side of history could have merged multiple directories into one,
+	 * if our side of history added the same file basename to each of
+	 * those directories, then all N of them would get implicitly
+	 * renamed by the directory rename detection into the same path,
+	 * and we'd get an add/add/.../add conflict, and all those adds
+	 * from *this* side of history.  This is not representable in the
+	 * index, and users aren't going to easily be able to make sense of
+	 * it.  So we need to provide a good warning about what's
+	 * happening, and fall back to no-directory-rename detection
+	 * behavior for those paths.
+	 *
+	 * See testcases 9e and all of section 5 from t6043 for examples.
+	 */
+	for (i = 0; i < pairs->nr; ++i) {
+		struct strmap_entry *rename_info;
+		struct collision_info *collision_info;
+		char *new_path;
+		struct diff_filepair *pair = pairs->queue[i];
+
+		if (pair->status != 'A' && pair->status != 'R')
+			continue;
+		rename_info = check_dir_renamed(pair->two->path, dir_renames);
+		if (!rename_info)
+			continue;
+
+		new_path = apply_dir_rename(rename_info, pair->two->path);
+		assert(new_path);
+		collision_info = strmap_get(collisions, new_path);
+		if (collision_info) {
+			free(new_path);
+		} else {
+			CALLOC_ARRAY(collision_info, 1);
+			string_list_init_nodup(&collision_info->source_files);
+			strmap_put(collisions, new_path, collision_info);
+		}
+		string_list_insert(&collision_info->source_files,
+				   pair->two->path);
+	}
+}
+
+static void free_collisions(struct strmap *collisions)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+
+	/* Free each value in the collisions map */
+	strmap_for_each_entry(collisions, &iter, entry) {
+		struct collision_info *info = entry->value;
+		string_list_clear(&info->source_files, 0);
+	}
+	/*
+	 * In compute_collisions(), we set collisions.strdup_strings to 0
+	 * so that we wouldn't have to make another copy of the new_path
+	 * allocated by apply_dir_rename().  But now that we've used them
+	 * and have no other references to these strings, it is time to
+	 * deallocate them.
+	 */
+	free_strmap_strings(collisions);
+	strmap_clear(collisions, 1);
+}
+
+static char *check_for_directory_rename(struct merge_options *opt,
+					const char *path,
+					unsigned side_index,
+					struct strmap *dir_renames,
+					struct strmap *dir_rename_exclusions,
+					struct strmap *collisions,
+					int *clean_merge)
+{
+	char *new_path;
+	struct strmap_entry *rename_info;
+	struct strmap_entry *otherinfo;
+	const char *new_dir;
+	int other_side = 3 - side_index;
+
+	/*
+	 * Cases where we don't have or don't want a directory rename for
+	 * this path.
+	 */
+	if (strmap_empty(dir_renames))
+		return NULL;
+	if (strmap_get(&collisions[other_side], path))
+		return NULL;
+	rename_info = check_dir_renamed(path, dir_renames);
+	if (!rename_info)
+		return NULL;
+
+	/*
+	 * This next part is a little weird.  We do not want to do an
+	 * implicit rename into a directory we renamed on our side, because
+	 * that will result in a spurious rename/rename(1to2) conflict.  An
+	 * example:
+	 *   Base commit: dumbdir/afile, otherdir/bfile
+	 *   Side 1:      smrtdir/afile, otherdir/bfile
+	 *   Side 2:      dumbdir/afile, dumbdir/bfile
+	 * Here, while working on Side 1, we could notice that otherdir was
+	 * renamed/merged to dumbdir, and change the diff_filepair for
+	 * otherdir/bfile into a rename into dumbdir/bfile.  However, Side
+	 * 2 will notice the rename from dumbdir to smrtdir, and do the
+	 * transitive rename to move it from dumbdir/bfile to
+	 * smrtdir/bfile.  That gives us bfile in dumbdir vs being in
+	 * smrtdir, a rename/rename(1to2) conflict.  We really just want
+	 * the file to end up in smrtdir.  And the way to achieve that is
+	 * to not let Side1 do the rename to dumbdir, since we know that is
+	 * the source of one of our directory renames.
+	 *
+	 * That's why otherinfo and dir_rename_exclusions is here.
+	 *
+	 * As it turns out, this also prevents N-way transient rename
+	 * confusion; See testcases 9c and 9d of t6043.
+	 */
+	new_dir = rename_info->value; /* old_dir = rename_info->key; */
+	otherinfo = strmap_get_entry(dir_rename_exclusions, new_dir);
+	if (otherinfo) {
+		path_msg(opt, INFO_DIR_RENAME_SKIPPED_DUE_TO_RERENAME, 1,
+			 rename_info->key, path, new_dir, NULL,
+			 _("WARNING: Avoiding applying %s -> %s rename "
+			   "to %s, because %s itself was renamed."),
+			 rename_info->key, new_dir, path, new_dir);
+		return NULL;
+	}
+
+	new_path = handle_path_level_conflicts(opt, path, side_index,
+					       rename_info,
+					       &collisions[side_index]);
+	*clean_merge &= (new_path != NULL);
+
+	return new_path;
+}
+
+static void apply_directory_rename_modifications(struct merge_options *opt,
+						 struct diff_filepair *pair,
+						 char *new_path)
+{
+	/*
+	 * The basic idea is to get the conflict_info from opt->priv->paths
+	 * at old path, and insert it into new_path; basically just this:
+	 *     ci = strmap_get(&opt->priv->paths, old_path);
+	 *     strmap_remove(&opt->priv->paths, old_path, 0);
+	 *     strmap_put(&opt->priv->paths, new_path, ci);
+	 * However, there are some factors complicating this:
+	 *     - opt->priv->paths may already have an entry at new_path
+	 *     - Each ci tracks its containing directory, so we need to
+	 *       update that
+	 *     - If another ci has the same containing directory, then
+	 *       the two char*'s MUST point to the same location.  See the
+	 *       comment in struct merged_info.  strcmp equality is not
+	 *       enough; we need pointer equality.
+	 *     - opt->priv->paths must hold the parent directories of any
+	 *       entries that are added.  So, if this directory rename
+	 *       causes entirely new directories, we must recursively add
+	 *       parent directories.
+	 *     - For each parent directory added to opt->priv->paths, we
+	 *       also need to get its parent directory stored in its
+	 *       conflict_info->merged.directory_name with all the same
+	 *       requirements about pointer equality.
+	 */
+	struct string_list dirs_to_insert = STRING_LIST_INIT_NODUP;
+	struct conflict_info *ci, *new_ci;
+	struct strmap_entry *entry;
+	const char *branch_with_new_path, *branch_with_dir_rename;
+	const char *old_path = pair->two->path;
+	const char *parent_name;
+	const char *cur_path;
+	int i, len;
+
+	entry = strmap_get_entry(&opt->priv->paths, old_path);
+	old_path = entry->key;
+	ci = entry->value;
+	VERIFY_CI(ci);
+
+	/* Find parent directories missing from opt->priv->paths */
+	cur_path = mem_pool_strdup(&opt->priv->pool, new_path);
+	free((char*)new_path);
+	new_path = (char *)cur_path;
+
+	while (1) {
+		/* Find the parent directory of cur_path */
+		char *last_slash = strrchr(cur_path, '/');
+		if (last_slash) {
+			parent_name = mem_pool_strndup(&opt->priv->pool,
+						       cur_path,
+						       last_slash - cur_path);
+		} else {
+			parent_name = opt->priv->toplevel_dir;
+			break;
+		}
+
+		/* Look it up in opt->priv->paths */
+		entry = strmap_get_entry(&opt->priv->paths, parent_name);
+		if (entry) {
+			parent_name = entry->key; /* reuse known pointer */
+			break;
+		}
+
+		/* Record this is one of the directories we need to insert */
+		string_list_append(&dirs_to_insert, parent_name);
+		cur_path = parent_name;
+	}
+
+	/* Traverse dirs_to_insert and insert them into opt->priv->paths */
+	for (i = dirs_to_insert.nr-1; i >= 0; --i) {
+		struct conflict_info *dir_ci;
+		char *cur_dir = dirs_to_insert.items[i].string;
+
+		CALLOC_ARRAY(dir_ci, 1);
+
+		dir_ci->merged.directory_name = parent_name;
+		len = strlen(parent_name);
+		/* len+1 because of trailing '/' character */
+		dir_ci->merged.basename_offset = (len > 0 ? len+1 : len);
+		dir_ci->dirmask = ci->filemask;
+		strmap_put(&opt->priv->paths, cur_dir, dir_ci);
+
+		parent_name = cur_dir;
+	}
+
+	assert(ci->filemask == 2 || ci->filemask == 4);
+	assert(ci->dirmask == 0 || ci->dirmask == 1);
+	if (ci->dirmask == 0)
+		strmap_remove(&opt->priv->paths, old_path, 0);
+	else {
+		/*
+		 * This file exists on one side, but we still had a directory
+		 * at the old location that we can't remove until after
+		 * processing all paths below it.  So, make a copy of ci in
+		 * new_ci and only put the file information into it.
+		 */
+		new_ci = mem_pool_calloc(&opt->priv->pool, 1, sizeof(*new_ci));
+		memcpy(new_ci, ci, sizeof(*ci));
+		assert(!new_ci->match_mask);
+		new_ci->dirmask = 0;
+		new_ci->stages[1].mode = 0;
+		oidcpy(&new_ci->stages[1].oid, null_oid());
+
+		/*
+		 * Now that we have the file information in new_ci, make sure
+		 * ci only has the directory information.
+		 */
+		ci->filemask = 0;
+		ci->merged.clean = 1;
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			if (ci->dirmask & (1 << i))
+				continue;
+			/* zero out any entries related to files */
+			ci->stages[i].mode = 0;
+			oidcpy(&ci->stages[i].oid, null_oid());
+		}
+
+		// Now we want to focus on new_ci, so reassign ci to it
+		ci = new_ci;
+	}
+
+	branch_with_new_path   = (ci->filemask == 2) ? opt->branch1 : opt->branch2;
+	branch_with_dir_rename = (ci->filemask == 2) ? opt->branch2 : opt->branch1;
+
+	/* Now, finally update ci and stick it into opt->priv->paths */
+	ci->merged.directory_name = parent_name;
+	len = strlen(parent_name);
+	ci->merged.basename_offset = (len > 0 ? len+1 : len);
+	new_ci = strmap_get(&opt->priv->paths, new_path);
+	if (!new_ci) {
+		/* Place ci back into opt->priv->paths, but at new_path */
+		strmap_put(&opt->priv->paths, new_path, ci);
+	} else {
+		int index;
+
+		/* A few sanity checks */
+		VERIFY_CI(new_ci);
+		assert(ci->filemask == 2 || ci->filemask == 4);
+		assert((new_ci->filemask & ci->filemask) == 0);
+		assert(!new_ci->merged.clean);
+
+		/* Copy stuff from ci into new_ci */
+		new_ci->filemask |= ci->filemask;
+		if (new_ci->dirmask)
+			new_ci->df_conflict = 1;
+		index = (ci->filemask >> 1);
+		new_ci->pathnames[index] = ci->pathnames[index];
+		new_ci->stages[index].mode = ci->stages[index].mode;
+		oidcpy(&new_ci->stages[index].oid, &ci->stages[index].oid);
+
+		ci = new_ci;
+	}
+
+	if (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE) {
+		/* Notify user of updated path */
+		if (pair->status == 'A')
+			path_msg(opt, INFO_DIR_RENAME_APPLIED, 1,
+				 new_path, old_path, NULL, NULL,
+				 _("Path updated: %s added in %s inside a "
+				   "directory that was renamed in %s; moving "
+				   "it to %s."),
+				 old_path, branch_with_new_path,
+				 branch_with_dir_rename, new_path);
+		else
+			path_msg(opt, INFO_DIR_RENAME_APPLIED, 1,
+				 new_path, old_path, NULL, NULL,
+				 _("Path updated: %s renamed to %s in %s, "
+				   "inside a directory that was renamed in %s; "
+				   "moving it to %s."),
+				 pair->one->path, old_path, branch_with_new_path,
+				 branch_with_dir_rename, new_path);
+	} else {
+		/*
+		 * opt->detect_directory_renames has the value
+		 * MERGE_DIRECTORY_RENAMES_CONFLICT, so mark these as conflicts.
+		 */
+		ci->path_conflict = 1;
+		if (pair->status == 'A')
+			path_msg(opt, CONFLICT_DIR_RENAME_SUGGESTED, 1,
+				 new_path, old_path, NULL, NULL,
+				 _("CONFLICT (file location): %s added in %s "
+				   "inside a directory that was renamed in %s, "
+				   "suggesting it should perhaps be moved to "
+				   "%s."),
+				 old_path, branch_with_new_path,
+				 branch_with_dir_rename, new_path);
+		else
+			path_msg(opt, CONFLICT_DIR_RENAME_SUGGESTED, 1,
+				 new_path, old_path, NULL, NULL,
+				 _("CONFLICT (file location): %s renamed to %s "
+				   "in %s, inside a directory that was renamed "
+				   "in %s, suggesting it should perhaps be "
+				   "moved to %s."),
+				 pair->one->path, old_path, branch_with_new_path,
+				 branch_with_dir_rename, new_path);
+	}
+
+	/*
+	 * Finally, record the new location.
+	 */
+	pair->two->path = new_path;
+}
+
+/*** Function Grouping: functions related to regular rename detection ***/
+
+static int process_renames(struct merge_options *opt,
+			   struct diff_queue_struct *renames)
+{
+	int clean_merge = 1, i;
+
+	for (i = 0; i < renames->nr; ++i) {
+		const char *oldpath = NULL, *newpath;
+		struct diff_filepair *pair = renames->queue[i];
+		struct conflict_info *oldinfo = NULL, *newinfo = NULL;
+		struct strmap_entry *old_ent, *new_ent;
+		unsigned int old_sidemask;
+		int target_index, other_source_index;
+		int source_deleted, collision, type_changed;
+		const char *rename_branch = NULL, *delete_branch = NULL;
+
+		old_ent = strmap_get_entry(&opt->priv->paths, pair->one->path);
+		new_ent = strmap_get_entry(&opt->priv->paths, pair->two->path);
+		if (old_ent) {
+			oldpath = old_ent->key;
+			oldinfo = old_ent->value;
+		}
+		newpath = pair->two->path;
+		if (new_ent) {
+			newpath = new_ent->key;
+			newinfo = new_ent->value;
+		}
+
+		/*
+		 * If pair->one->path isn't in opt->priv->paths, that means
+		 * that either directory rename detection removed that
+		 * path, or a parent directory of oldpath was resolved and
+		 * we don't even need the rename; in either case, we can
+		 * skip it.  If oldinfo->merged.clean, then the other side
+		 * of history had no changes to oldpath and we don't need
+		 * the rename and can skip it.
+		 */
+		if (!oldinfo || oldinfo->merged.clean)
+			continue;
+
+		/*
+		 * diff_filepairs have copies of pathnames, thus we have to
+		 * use standard 'strcmp()' (negated) instead of '=='.
+		 */
+		if (i + 1 < renames->nr &&
+		    !strcmp(oldpath, renames->queue[i+1]->one->path)) {
+			/* Handle rename/rename(1to2) or rename/rename(1to1) */
+			const char *pathnames[3];
+			struct version_info merged;
+			struct conflict_info *base, *side1, *side2;
+			unsigned was_binary_blob = 0;
+
+			pathnames[0] = oldpath;
+			pathnames[1] = newpath;
+			pathnames[2] = renames->queue[i+1]->two->path;
+
+			base = strmap_get(&opt->priv->paths, pathnames[0]);
+			side1 = strmap_get(&opt->priv->paths, pathnames[1]);
+			side2 = strmap_get(&opt->priv->paths, pathnames[2]);
+
+			VERIFY_CI(base);
+			VERIFY_CI(side1);
+			VERIFY_CI(side2);
+
+			if (!strcmp(pathnames[1], pathnames[2])) {
+				struct rename_info *ri = &opt->priv->renames;
+				int j;
+
+				/* Both sides renamed the same way */
+				assert(side1 == side2);
+				memcpy(&side1->stages[0], &base->stages[0],
+				       sizeof(merged));
+				side1->filemask |= (1 << MERGE_BASE);
+				/* Mark base as resolved by removal */
+				base->merged.is_null = 1;
+				base->merged.clean = 1;
+
+				/*
+				 * Disable remembering renames optimization;
+				 * rename/rename(1to1) is incredibly rare, and
+				 * just disabling the optimization is easier
+				 * than purging cached_pairs,
+				 * cached_target_names, and dir_rename_counts.
+				 */
+				for (j = 0; j < 3; j++)
+					ri->merge_trees[j] = NULL;
+
+				/* We handled both renames, i.e. i+1 handled */
+				i++;
+				/* Move to next rename */
+				continue;
+			}
+
+			/* This is a rename/rename(1to2) */
+			clean_merge = handle_content_merge(opt,
+							   pair->one->path,
+							   &base->stages[0],
+							   &side1->stages[1],
+							   &side2->stages[2],
+							   pathnames,
+							   1 + 2 * opt->priv->call_depth,
+							   &merged);
+			if (clean_merge < 0)
+				return -1;
+			if (!clean_merge &&
+			    merged.mode == side1->stages[1].mode &&
+			    oideq(&merged.oid, &side1->stages[1].oid))
+				was_binary_blob = 1;
+			memcpy(&side1->stages[1], &merged, sizeof(merged));
+			if (was_binary_blob) {
+				/*
+				 * Getting here means we were attempting to
+				 * merge a binary blob.
+				 *
+				 * Since we can't merge binaries,
+				 * handle_content_merge() just takes one
+				 * side.  But we don't want to copy the
+				 * contents of one side to both paths.  We
+				 * used the contents of side1 above for
+				 * side1->stages, let's use the contents of
+				 * side2 for side2->stages below.
+				 */
+				oidcpy(&merged.oid, &side2->stages[2].oid);
+				merged.mode = side2->stages[2].mode;
+			}
+			memcpy(&side2->stages[2], &merged, sizeof(merged));
+
+			side1->path_conflict = 1;
+			side2->path_conflict = 1;
+			/*
+			 * TODO: For renames we normally remove the path at the
+			 * old name.  It would thus seem consistent to do the
+			 * same for rename/rename(1to2) cases, but we haven't
+			 * done so traditionally and a number of the regression
+			 * tests now encode an expectation that the file is
+			 * left there at stage 1.  If we ever decide to change
+			 * this, add the following two lines here:
+			 *    base->merged.is_null = 1;
+			 *    base->merged.clean = 1;
+			 * and remove the setting of base->path_conflict to 1.
+			 */
+			base->path_conflict = 1;
+			path_msg(opt, CONFLICT_RENAME_RENAME, 0,
+				 pathnames[0], pathnames[1], pathnames[2], NULL,
+				 _("CONFLICT (rename/rename): %s renamed to "
+				   "%s in %s and to %s in %s."),
+				 pathnames[0],
+				 pathnames[1], opt->branch1,
+				 pathnames[2], opt->branch2);
+
+			i++; /* We handled both renames, i.e. i+1 handled */
+			continue;
+		}
+
+		VERIFY_CI(oldinfo);
+		VERIFY_CI(newinfo);
+		target_index = pair->score; /* from collect_renames() */
+		assert(target_index == 1 || target_index == 2);
+		other_source_index = 3 - target_index;
+		old_sidemask = (1 << other_source_index); /* 2 or 4 */
+		source_deleted = (oldinfo->filemask == 1);
+		collision = ((newinfo->filemask & old_sidemask) != 0);
+		type_changed = !source_deleted &&
+			(S_ISREG(oldinfo->stages[other_source_index].mode) !=
+			 S_ISREG(newinfo->stages[target_index].mode));
+		if (type_changed && collision) {
+			/*
+			 * special handling so later blocks can handle this...
+			 *
+			 * if type_changed && collision are both true, then this
+			 * was really a double rename, but one side wasn't
+			 * detected due to lack of break detection.  I.e.
+			 * something like
+			 *    orig: has normal file 'foo'
+			 *    side1: renames 'foo' to 'bar', adds 'foo' symlink
+			 *    side2: renames 'foo' to 'bar'
+			 * In this case, the foo->bar rename on side1 won't be
+			 * detected because the new symlink named 'foo' is
+			 * there and we don't do break detection.  But we detect
+			 * this here because we don't want to merge the content
+			 * of the foo symlink with the foo->bar file, so we
+			 * have some logic to handle this special case.  The
+			 * easiest way to do that is make 'bar' on side1 not
+			 * be considered a colliding file but the other part
+			 * of a normal rename.  If the file is very different,
+			 * well we're going to get content merge conflicts
+			 * anyway so it doesn't hurt.  And if the colliding
+			 * file also has a different type, that'll be handled
+			 * by the content merge logic in process_entry() too.
+			 *
+			 * See also t6430, 'rename vs. rename/symlink'
+			 */
+			collision = 0;
+		}
+		if (source_deleted) {
+			if (target_index == 1) {
+				rename_branch = opt->branch1;
+				delete_branch = opt->branch2;
+			} else {
+				rename_branch = opt->branch2;
+				delete_branch = opt->branch1;
+			}
+		}
+
+		assert(source_deleted || oldinfo->filemask & old_sidemask);
+
+		/* Need to check for special types of rename conflicts... */
+		if (collision && !source_deleted) {
+			/* collision: rename/add or rename/rename(2to1) */
+			const char *pathnames[3];
+			struct version_info merged;
+
+			struct conflict_info *base, *side1, *side2;
+			int clean;
+
+			pathnames[0] = oldpath;
+			pathnames[other_source_index] = oldpath;
+			pathnames[target_index] = newpath;
+
+			base = strmap_get(&opt->priv->paths, pathnames[0]);
+			side1 = strmap_get(&opt->priv->paths, pathnames[1]);
+			side2 = strmap_get(&opt->priv->paths, pathnames[2]);
+
+			VERIFY_CI(base);
+			VERIFY_CI(side1);
+			VERIFY_CI(side2);
+
+			clean = handle_content_merge(opt, pair->one->path,
+						     &base->stages[0],
+						     &side1->stages[1],
+						     &side2->stages[2],
+						     pathnames,
+						     1 + 2 * opt->priv->call_depth,
+						     &merged);
+			if (clean < 0)
+				return -1;
+
+			memcpy(&newinfo->stages[target_index], &merged,
+			       sizeof(merged));
+			if (!clean) {
+				path_msg(opt, CONFLICT_RENAME_COLLIDES, 0,
+					 newpath, oldpath, NULL, NULL,
+					 _("CONFLICT (rename involved in "
+					   "collision): rename of %s -> %s has "
+					   "content conflicts AND collides "
+					   "with another path; this may result "
+					   "in nested conflict markers."),
+					 oldpath, newpath);
+			}
+		} else if (collision && source_deleted) {
+			/*
+			 * rename/add/delete or rename/rename(2to1)/delete:
+			 * since oldpath was deleted on the side that didn't
+			 * do the rename, there's not much of a content merge
+			 * we can do for the rename.  oldinfo->merged.is_null
+			 * was already set, so we just leave things as-is so
+			 * they look like an add/add conflict.
+			 */
+
+			newinfo->path_conflict = 1;
+			path_msg(opt, CONFLICT_RENAME_DELETE, 0,
+				 newpath, oldpath, NULL, NULL,
+				 _("CONFLICT (rename/delete): %s renamed "
+				   "to %s in %s, but deleted in %s."),
+				 oldpath, newpath, rename_branch, delete_branch);
+		} else {
+			/*
+			 * a few different cases...start by copying the
+			 * existing stage(s) from oldinfo over the newinfo
+			 * and update the pathname(s).
+			 */
+			memcpy(&newinfo->stages[0], &oldinfo->stages[0],
+			       sizeof(newinfo->stages[0]));
+			newinfo->filemask |= (1 << MERGE_BASE);
+			newinfo->pathnames[0] = oldpath;
+			if (type_changed) {
+				/* rename vs. typechange */
+				/* Mark the original as resolved by removal */
+				memcpy(&oldinfo->stages[0].oid, null_oid(),
+				       sizeof(oldinfo->stages[0].oid));
+				oldinfo->stages[0].mode = 0;
+				oldinfo->filemask &= 0x06;
+			} else if (source_deleted) {
+				/* rename/delete */
+				newinfo->path_conflict = 1;
+				path_msg(opt, CONFLICT_RENAME_DELETE, 0,
+					 newpath, oldpath, NULL, NULL,
+					 _("CONFLICT (rename/delete): %s renamed"
+					   " to %s in %s, but deleted in %s."),
+					 oldpath, newpath,
+					 rename_branch, delete_branch);
+			} else {
+				/* normal rename */
+				memcpy(&newinfo->stages[other_source_index],
+				       &oldinfo->stages[other_source_index],
+				       sizeof(newinfo->stages[0]));
+				newinfo->filemask |= (1 << other_source_index);
+				newinfo->pathnames[other_source_index] = oldpath;
+			}
+		}
+
+		if (!type_changed) {
+			/* Mark the original as resolved by removal */
+			oldinfo->merged.is_null = 1;
+			oldinfo->merged.clean = 1;
+		}
+
+	}
+
+	return clean_merge;
+}
+
+static inline int possible_side_renames(struct rename_info *renames,
+					unsigned side_index)
+{
+	return renames->pairs[side_index].nr > 0 &&
+	       !strintmap_empty(&renames->relevant_sources[side_index]);
+}
+
+static inline int possible_renames(struct rename_info *renames)
+{
+	return possible_side_renames(renames, 1) ||
+	       possible_side_renames(renames, 2) ||
+	       !strmap_empty(&renames->cached_pairs[1]) ||
+	       !strmap_empty(&renames->cached_pairs[2]);
+}
+
+static void resolve_diffpair_statuses(struct diff_queue_struct *q)
+{
+	/*
+	 * A simplified version of diff_resolve_rename_copy(); would probably
+	 * just use that function but it's static...
+	 */
+	int i;
+	struct diff_filepair *p;
+
+	for (i = 0; i < q->nr; ++i) {
+		p = q->queue[i];
+		p->status = 0; /* undecided */
+		if (!DIFF_FILE_VALID(p->one))
+			p->status = DIFF_STATUS_ADDED;
+		else if (!DIFF_FILE_VALID(p->two))
+			p->status = DIFF_STATUS_DELETED;
+		else if (DIFF_PAIR_RENAME(p))
+			p->status = DIFF_STATUS_RENAMED;
+	}
+}
+
+static void prune_cached_from_relevant(struct rename_info *renames,
+				       unsigned side)
+{
+	/* Reason for this function described in add_pair() */
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+
+	/* Remove from relevant_sources all entries in cached_pairs[side] */
+	strmap_for_each_entry(&renames->cached_pairs[side], &iter, entry) {
+		strintmap_remove(&renames->relevant_sources[side],
+				 entry->key);
+	}
+	/* Remove from relevant_sources all entries in cached_irrelevant[side] */
+	strset_for_each_entry(&renames->cached_irrelevant[side], &iter, entry) {
+		strintmap_remove(&renames->relevant_sources[side],
+				 entry->key);
+	}
+}
+
+static void use_cached_pairs(struct merge_options *opt,
+			     struct strmap *cached_pairs,
+			     struct diff_queue_struct *pairs)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *entry;
+
+	/*
+	 * Add to side_pairs all entries from renames->cached_pairs[side_index].
+	 * (Info in cached_irrelevant[side_index] is not relevant here.)
+	 */
+	strmap_for_each_entry(cached_pairs, &iter, entry) {
+		struct diff_filespec *one, *two;
+		const char *old_name = entry->key;
+		const char *new_name = entry->value;
+		if (!new_name)
+			new_name = old_name;
+
+		/*
+		 * cached_pairs has *copies* of old_name and new_name,
+		 * because it has to persist across merges.  Since
+		 * pool_alloc_filespec() will just re-use the existing
+		 * filenames, which will also get re-used by
+		 * opt->priv->paths if they become renames, and then
+		 * get freed at the end of the merge, that would leave
+		 * the copy in cached_pairs dangling.  Avoid this by
+		 * making a copy here.
+		 */
+		old_name = mem_pool_strdup(&opt->priv->pool, old_name);
+		new_name = mem_pool_strdup(&opt->priv->pool, new_name);
+
+		/* We don't care about oid/mode, only filenames and status */
+		one = pool_alloc_filespec(&opt->priv->pool, old_name);
+		two = pool_alloc_filespec(&opt->priv->pool, new_name);
+		pool_diff_queue(&opt->priv->pool, pairs, one, two);
+		pairs->queue[pairs->nr-1]->status = entry->value ? 'R' : 'D';
+	}
+}
+
+static void cache_new_pair(struct rename_info *renames,
+			   int side,
+			   char *old_path,
+			   char *new_path,
+			   int free_old_value)
+{
+	char *old_value;
+	new_path = xstrdup(new_path);
+	old_value = strmap_put(&renames->cached_pairs[side],
+			       old_path, new_path);
+	strset_add(&renames->cached_target_names[side], new_path);
+	if (free_old_value)
+		free(old_value);
+	else
+		assert(!old_value);
+}
+
+static void possibly_cache_new_pair(struct rename_info *renames,
+				    struct diff_filepair *p,
+				    unsigned side,
+				    char *new_path)
+{
+	int dir_renamed_side = 0;
+
+	if (new_path) {
+		/*
+		 * Directory renames happen on the other side of history from
+		 * the side that adds new files to the old directory.
+		 */
+		dir_renamed_side = 3 - side;
+	} else {
+		int val = strintmap_get(&renames->relevant_sources[side],
+					p->one->path);
+		if (val == RELEVANT_NO_MORE) {
+			assert(p->status == 'D');
+			strset_add(&renames->cached_irrelevant[side],
+				   p->one->path);
+		}
+		if (val <= 0)
+			return;
+	}
+
+	if (p->status == 'D') {
+		/*
+		 * If we already had this delete, we'll just set it's value
+		 * to NULL again, so no harm.
+		 */
+		strmap_put(&renames->cached_pairs[side], p->one->path, NULL);
+	} else if (p->status == 'R') {
+		if (!new_path)
+			new_path = p->two->path;
+		else
+			cache_new_pair(renames, dir_renamed_side,
+				       p->two->path, new_path, 0);
+		cache_new_pair(renames, side, p->one->path, new_path, 1);
+	} else if (p->status == 'A' && new_path) {
+		cache_new_pair(renames, dir_renamed_side,
+			       p->two->path, new_path, 0);
+	}
+}
+
+static int compare_pairs(const void *a_, const void *b_)
+{
+	const struct diff_filepair *a = *((const struct diff_filepair **)a_);
+	const struct diff_filepair *b = *((const struct diff_filepair **)b_);
+
+	return strcmp(a->one->path, b->one->path);
+}
+
+/* Call diffcore_rename() to update deleted/added pairs into rename pairs */
+static int detect_regular_renames(struct merge_options *opt,
+				  unsigned side_index)
+{
+	struct diff_options diff_opts;
+	struct rename_info *renames = &opt->priv->renames;
+
+	prune_cached_from_relevant(renames, side_index);
+	if (!possible_side_renames(renames, side_index)) {
+		/*
+		 * No rename detection needed for this side, but we still need
+		 * to make sure 'adds' are marked correctly in case the other
+		 * side had directory renames.
+		 */
+		resolve_diffpair_statuses(&renames->pairs[side_index]);
+		return 0;
+	}
+
+	partial_clear_dir_rename_count(&renames->dir_rename_count[side_index]);
+	repo_diff_setup(opt->repo, &diff_opts);
+	diff_opts.flags.recursive = 1;
+	diff_opts.flags.rename_empty = 0;
+	diff_opts.detect_rename = DIFF_DETECT_RENAME;
+	diff_opts.rename_limit = opt->rename_limit;
+	if (opt->rename_limit <= 0)
+		diff_opts.rename_limit = 7000;
+	diff_opts.rename_score = opt->rename_score;
+	diff_opts.show_rename_progress = opt->show_rename_progress;
+	diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
+	diff_setup_done(&diff_opts);
+
+	diff_queued_diff = renames->pairs[side_index];
+	trace2_region_enter("diff", "diffcore_rename", opt->repo);
+	diffcore_rename_extended(&diff_opts,
+				 &opt->priv->pool,
+				 &renames->relevant_sources[side_index],
+				 &renames->dirs_removed[side_index],
+				 &renames->dir_rename_count[side_index],
+				 &renames->cached_pairs[side_index]);
+	trace2_region_leave("diff", "diffcore_rename", opt->repo);
+	resolve_diffpair_statuses(&diff_queued_diff);
+
+	if (diff_opts.needed_rename_limit > 0)
+		renames->redo_after_renames = 0;
+	if (diff_opts.needed_rename_limit > renames->needed_limit)
+		renames->needed_limit = diff_opts.needed_rename_limit;
+
+	renames->pairs[side_index] = diff_queued_diff;
+
+	diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
+	diff_queued_diff.nr = 0;
+	diff_queued_diff.queue = NULL;
+	diff_flush(&diff_opts);
+
+	return 1;
+}
+
+/*
+ * Get information of all renames which occurred in 'side_pairs', making use
+ * of any implicit directory renames in side_dir_renames (also making use of
+ * implicit directory renames rename_exclusions as needed by
+ * check_for_directory_rename()).  Add all (updated) renames into result.
+ */
+static int collect_renames(struct merge_options *opt,
+			   struct diff_queue_struct *result,
+			   unsigned side_index,
+			   struct strmap *collisions,
+			   struct strmap *dir_renames_for_side,
+			   struct strmap *rename_exclusions)
+{
+	int i, clean = 1;
+	struct diff_queue_struct *side_pairs;
+	struct rename_info *renames = &opt->priv->renames;
+
+	side_pairs = &renames->pairs[side_index];
+
+	for (i = 0; i < side_pairs->nr; ++i) {
+		struct diff_filepair *p = side_pairs->queue[i];
+		char *new_path; /* non-NULL only with directory renames */
+
+		if (p->status != 'A' && p->status != 'R') {
+			possibly_cache_new_pair(renames, p, side_index, NULL);
+			pool_diff_free_filepair(&opt->priv->pool, p);
+			continue;
+		}
+
+		new_path = check_for_directory_rename(opt, p->two->path,
+						      side_index,
+						      dir_renames_for_side,
+						      rename_exclusions,
+						      collisions,
+						      &clean);
+
+		possibly_cache_new_pair(renames, p, side_index, new_path);
+		if (p->status != 'R' && !new_path) {
+			pool_diff_free_filepair(&opt->priv->pool, p);
+			continue;
+		}
+
+		if (new_path)
+			apply_directory_rename_modifications(opt, p, new_path);
+
+		/*
+		 * p->score comes back from diffcore_rename_extended() with
+		 * the similarity of the renamed file.  The similarity is
+		 * was used to determine that the two files were related
+		 * and are a rename, which we have already used, but beyond
+		 * that we have no use for the similarity.  So p->score is
+		 * now irrelevant.  However, process_renames() will need to
+		 * know which side of the merge this rename was associated
+		 * with, so overwrite p->score with that value.
+		 */
+		p->score = side_index;
+		result->queue[result->nr++] = p;
+	}
+
+	return clean;
+}
+
+static int detect_and_process_renames(struct merge_options *opt,
+				      struct tree *merge_base,
+				      struct tree *side1,
+				      struct tree *side2)
+{
+	struct diff_queue_struct combined = { 0 };
+	struct rename_info *renames = &opt->priv->renames;
+	struct strmap collisions[3];
+	int need_dir_renames, s, i, clean = 1;
+	unsigned detection_run = 0;
+
+	if (!possible_renames(renames))
+		goto cleanup;
+
+	trace2_region_enter("merge", "regular renames", opt->repo);
+	detection_run |= detect_regular_renames(opt, MERGE_SIDE1);
+	detection_run |= detect_regular_renames(opt, MERGE_SIDE2);
+	if (renames->needed_limit) {
+		renames->cached_pairs_valid_side = 0;
+		renames->redo_after_renames = 0;
+	}
+	if (renames->redo_after_renames && detection_run) {
+		int i, side;
+		struct diff_filepair *p;
+
+		/* Cache the renames, we found */
+		for (side = MERGE_SIDE1; side <= MERGE_SIDE2; side++) {
+			for (i = 0; i < renames->pairs[side].nr; ++i) {
+				p = renames->pairs[side].queue[i];
+				possibly_cache_new_pair(renames, p, side, NULL);
+			}
+		}
+
+		/* Restart the merge with the cached renames */
+		renames->redo_after_renames = 2;
+		trace2_region_leave("merge", "regular renames", opt->repo);
+		goto cleanup;
+	}
+	use_cached_pairs(opt, &renames->cached_pairs[1], &renames->pairs[1]);
+	use_cached_pairs(opt, &renames->cached_pairs[2], &renames->pairs[2]);
+	trace2_region_leave("merge", "regular renames", opt->repo);
+
+	trace2_region_enter("merge", "directory renames", opt->repo);
+	need_dir_renames =
+	  !opt->priv->call_depth &&
+	  (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE ||
+	   opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_CONFLICT);
+
+	if (need_dir_renames) {
+		get_provisional_directory_renames(opt, MERGE_SIDE1, &clean);
+		get_provisional_directory_renames(opt, MERGE_SIDE2, &clean);
+		handle_directory_level_conflicts(opt);
+	}
+
+	ALLOC_GROW(combined.queue,
+		   renames->pairs[1].nr + renames->pairs[2].nr,
+		   combined.alloc);
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
+		int other_side = 3 - i;
+		compute_collisions(&collisions[i],
+				   &renames->dir_renames[other_side],
+				   &renames->pairs[i]);
+	}
+	clean &= collect_renames(opt, &combined, MERGE_SIDE1,
+				 collisions,
+				 &renames->dir_renames[2],
+				 &renames->dir_renames[1]);
+	clean &= collect_renames(opt, &combined, MERGE_SIDE2,
+				 collisions,
+				 &renames->dir_renames[1],
+				 &renames->dir_renames[2]);
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++)
+		free_collisions(&collisions[i]);
+	STABLE_QSORT(combined.queue, combined.nr, compare_pairs);
+	trace2_region_leave("merge", "directory renames", opt->repo);
+
+	trace2_region_enter("merge", "process renames", opt->repo);
+	clean &= process_renames(opt, &combined);
+	trace2_region_leave("merge", "process renames", opt->repo);
+
+	goto simple_cleanup; /* collect_renames() handles some of cleanup */
+
+cleanup:
+	/*
+	 * Free now unneeded filepairs, which would have been handled
+	 * in collect_renames() normally but we skipped that code.
+	 */
+	for (s = MERGE_SIDE1; s <= MERGE_SIDE2; s++) {
+		struct diff_queue_struct *side_pairs;
+		int i;
+
+		side_pairs = &renames->pairs[s];
+		for (i = 0; i < side_pairs->nr; ++i) {
+			struct diff_filepair *p = side_pairs->queue[i];
+			pool_diff_free_filepair(&opt->priv->pool, p);
+		}
+	}
+
+simple_cleanup:
+	/* Free memory for renames->pairs[] and combined */
+	for (s = MERGE_SIDE1; s <= MERGE_SIDE2; s++) {
+		free(renames->pairs[s].queue);
+		DIFF_QUEUE_CLEAR(&renames->pairs[s]);
+	}
+	for (i = 0; i < combined.nr; i++)
+		pool_diff_free_filepair(&opt->priv->pool, combined.queue[i]);
+	free(combined.queue);
+
+	return clean;
+}
+
+/*** Function Grouping: functions related to process_entries() ***/
+
+static int sort_dirs_next_to_their_children(const char *one, const char *two)
+{
+	unsigned char c1, c2;
+
+	/*
+	 * Here we only care that entries for directories appear adjacent
+	 * to and before files underneath the directory.  We can achieve
+	 * that by pretending to add a trailing slash to every file and
+	 * then sorting.  In other words, we do not want the natural
+	 * sorting of
+	 *     foo
+	 *     foo.txt
+	 *     foo/bar
+	 * Instead, we want "foo" to sort as though it were "foo/", so that
+	 * we instead get
+	 *     foo.txt
+	 *     foo
+	 *     foo/bar
+	 * To achieve this, we basically implement our own strcmp, except that
+	 * if we get to the end of either string instead of comparing NUL to
+	 * another character, we compare '/' to it.
+	 *
+	 * If this unusual "sort as though '/' were appended" perplexes
+	 * you, perhaps it will help to note that this is not the final
+	 * sort.  write_tree() will sort again without the trailing slash
+	 * magic, but just on paths immediately under a given tree.
+	 *
+	 * The reason to not use df_name_compare directly was that it was
+	 * just too expensive (we don't have the string lengths handy), so
+	 * it was reimplemented.
+	 */
+
+	/*
+	 * NOTE: This function will never be called with two equal strings,
+	 * because it is used to sort the keys of a strmap, and strmaps have
+	 * unique keys by construction.  That simplifies our c1==c2 handling
+	 * below.
+	 */
+
+	while (*one && (*one == *two)) {
+		one++;
+		two++;
+	}
+
+	c1 = *one ? *one : '/';
+	c2 = *two ? *two : '/';
+
+	if (c1 == c2) {
+		/* Getting here means one is a leading directory of the other */
+		return (*one) ? 1 : -1;
+	} else
+		return c1 - c2;
+}
+
+static int read_oid_strbuf(struct merge_options *opt,
+			   const struct object_id *oid,
+			   struct strbuf *dst)
+{
+	void *buf;
+	enum object_type type;
+	unsigned long size;
+	buf = read_object_file(oid, &type, &size);
+	if (!buf)
+		return err(opt, _("cannot read object %s"), oid_to_hex(oid));
+	if (type != OBJ_BLOB) {
+		free(buf);
+		return err(opt, _("object %s is not a blob"), oid_to_hex(oid));
+	}
+	strbuf_attach(dst, buf, size, size + 1);
+	return 0;
+}
+
+static int blob_unchanged(struct merge_options *opt,
+			  const struct version_info *base,
+			  const struct version_info *side,
+			  const char *path)
+{
+	struct strbuf basebuf = STRBUF_INIT;
+	struct strbuf sidebuf = STRBUF_INIT;
+	int ret = 0; /* assume changed for safety */
+	struct index_state *idx = &opt->priv->attr_index;
+
+	if (!idx->initialized)
+		initialize_attr_index(opt);
+
+	if (base->mode != side->mode)
+		return 0;
+	if (oideq(&base->oid, &side->oid))
+		return 1;
+
+	if (read_oid_strbuf(opt, &base->oid, &basebuf) ||
+	    read_oid_strbuf(opt, &side->oid, &sidebuf))
+		goto error_return;
+	/*
+	 * Note: binary | is used so that both renormalizations are
+	 * performed.  Comparison can be skipped if both files are
+	 * unchanged since their sha1s have already been compared.
+	 */
+	if (renormalize_buffer(idx, path, basebuf.buf, basebuf.len, &basebuf) |
+	    renormalize_buffer(idx, path, sidebuf.buf, sidebuf.len, &sidebuf))
+		ret = (basebuf.len == sidebuf.len &&
+		       !memcmp(basebuf.buf, sidebuf.buf, basebuf.len));
+
+error_return:
+	strbuf_release(&basebuf);
+	strbuf_release(&sidebuf);
+	return ret;
+}
+
+struct directory_versions {
+	/*
+	 * versions: list of (basename -> version_info)
+	 *
+	 * The basenames are in reverse lexicographic order of full pathnames,
+	 * as processed in process_entries().  This puts all entries within
+	 * a directory together, and covers the directory itself after
+	 * everything within it, allowing us to write subtrees before needing
+	 * to record information for the tree itself.
+	 */
+	struct string_list versions;
+
+	/*
+	 * offsets: list of (full relative path directories -> integer offsets)
+	 *
+	 * Since versions contains basenames from files in multiple different
+	 * directories, we need to know which entries in versions correspond
+	 * to which directories.  Values of e.g.
+	 *     ""             0
+	 *     src            2
+	 *     src/moduleA    5
+	 * Would mean that entries 0-1 of versions are files in the toplevel
+	 * directory, entries 2-4 are files under src/, and the remaining
+	 * entries starting at index 5 are files under src/moduleA/.
+	 */
+	struct string_list offsets;
+
+	/*
+	 * last_directory: directory that previously processed file found in
+	 *
+	 * last_directory starts NULL, but records the directory in which the
+	 * previous file was found within.  As soon as
+	 *    directory(current_file) != last_directory
+	 * then we need to start updating accounting in versions & offsets.
+	 * Note that last_directory is always the last path in "offsets" (or
+	 * NULL if "offsets" is empty) so this exists just for quick access.
+	 */
+	const char *last_directory;
+
+	/* last_directory_len: cached computation of strlen(last_directory) */
+	unsigned last_directory_len;
+};
+
+static int tree_entry_order(const void *a_, const void *b_)
+{
+	const struct string_list_item *a = a_;
+	const struct string_list_item *b = b_;
+
+	const struct merged_info *ami = a->util;
+	const struct merged_info *bmi = b->util;
+	return base_name_compare(a->string, strlen(a->string), ami->result.mode,
+				 b->string, strlen(b->string), bmi->result.mode);
+}
+
+static int write_tree(struct object_id *result_oid,
+		      struct string_list *versions,
+		      unsigned int offset,
+		      size_t hash_size)
+{
+	size_t maxlen = 0, extra;
+	unsigned int nr;
+	struct strbuf buf = STRBUF_INIT;
+	int i, ret = 0;
+
+	assert(offset <= versions->nr);
+	nr = versions->nr - offset;
+	if (versions->nr)
+		/* No need for STABLE_QSORT -- filenames must be unique */
+		QSORT(versions->items + offset, nr, tree_entry_order);
+
+	/* Pre-allocate some space in buf */
+	extra = hash_size + 8; /* 8: 6 for mode, 1 for space, 1 for NUL char */
+	for (i = 0; i < nr; i++) {
+		maxlen += strlen(versions->items[offset+i].string) + extra;
+	}
+	strbuf_grow(&buf, maxlen);
+
+	/* Write each entry out to buf */
+	for (i = 0; i < nr; i++) {
+		struct merged_info *mi = versions->items[offset+i].util;
+		struct version_info *ri = &mi->result;
+		strbuf_addf(&buf, "%o %s%c",
+			    ri->mode,
+			    versions->items[offset+i].string, '\0');
+		strbuf_add(&buf, ri->oid.hash, hash_size);
+	}
+
+	/* Write this object file out, and record in result_oid */
+	if (write_object_file(buf.buf, buf.len, OBJ_TREE, result_oid))
+		ret = -1;
+	strbuf_release(&buf);
+	return ret;
+}
+
+static void record_entry_for_tree(struct directory_versions *dir_metadata,
+				  const char *path,
+				  struct merged_info *mi)
+{
+	const char *basename;
+
+	if (mi->is_null)
+		/* nothing to record */
+		return;
+
+	basename = path + mi->basename_offset;
+	assert(strchr(basename, '/') == NULL);
+	string_list_append(&dir_metadata->versions,
+			   basename)->util = &mi->result;
+}
+
+static int write_completed_directory(struct merge_options *opt,
+				     const char *new_directory_name,
+				     struct directory_versions *info)
+{
+	const char *prev_dir;
+	struct merged_info *dir_info = NULL;
+	unsigned int offset, ret = 0;
+
+	/*
+	 * Some explanation of info->versions and info->offsets...
+	 *
+	 * process_entries() iterates over all relevant files AND
+	 * directories in reverse lexicographic order, and calls this
+	 * function.  Thus, an example of the paths that process_entries()
+	 * could operate on (along with the directories for those paths
+	 * being shown) is:
+	 *
+	 *     xtract.c             ""
+	 *     tokens.txt           ""
+	 *     src/moduleB/umm.c    src/moduleB
+	 *     src/moduleB/stuff.h  src/moduleB
+	 *     src/moduleB/baz.c    src/moduleB
+	 *     src/moduleB          src
+	 *     src/moduleA/foo.c    src/moduleA
+	 *     src/moduleA/bar.c    src/moduleA
+	 *     src/moduleA          src
+	 *     src                  ""
+	 *     Makefile             ""
+	 *
+	 * info->versions:
+	 *
+	 *     always contains the unprocessed entries and their
+	 *     version_info information.  For example, after the first five
+	 *     entries above, info->versions would be:
+	 *
+	 *     	   xtract.c     <xtract.c's version_info>
+	 *     	   token.txt    <token.txt's version_info>
+	 *     	   umm.c        <src/moduleB/umm.c's version_info>
+	 *     	   stuff.h      <src/moduleB/stuff.h's version_info>
+	 *     	   baz.c        <src/moduleB/baz.c's version_info>
+	 *
+	 *     Once a subdirectory is completed we remove the entries in
+	 *     that subdirectory from info->versions, writing it as a tree
+	 *     (write_tree()).  Thus, as soon as we get to src/moduleB,
+	 *     info->versions would be updated to
+	 *
+	 *     	   xtract.c     <xtract.c's version_info>
+	 *     	   token.txt    <token.txt's version_info>
+	 *     	   moduleB      <src/moduleB's version_info>
+	 *
+	 * info->offsets:
+	 *
+	 *     helps us track which entries in info->versions correspond to
+	 *     which directories.  When we are N directories deep (e.g. 4
+	 *     for src/modA/submod/subdir/), we have up to N+1 unprocessed
+	 *     directories (+1 because of toplevel dir).  Corresponding to
+	 *     the info->versions example above, after processing five entries
+	 *     info->offsets will be:
+	 *
+	 *     	   ""           0
+	 *     	   src/moduleB  2
+	 *
+	 *     which is used to know that xtract.c & token.txt are from the
+	 *     toplevel dirctory, while umm.c & stuff.h & baz.c are from the
+	 *     src/moduleB directory.  Again, following the example above,
+	 *     once we need to process src/moduleB, then info->offsets is
+	 *     updated to
+	 *
+	 *     	   ""           0
+	 *     	   src          2
+	 *
+	 *     which says that moduleB (and only moduleB so far) is in the
+	 *     src directory.
+	 *
+	 *     One unique thing to note about info->offsets here is that
+	 *     "src" was not added to info->offsets until there was a path
+	 *     (a file OR directory) immediately below src/ that got
+	 *     processed.
+	 *
+	 * Since process_entry() just appends new entries to info->versions,
+	 * write_completed_directory() only needs to do work if the next path
+	 * is in a directory that is different than the last directory found
+	 * in info->offsets.
+	 */
+
+	/*
+	 * If we are working with the same directory as the last entry, there
+	 * is no work to do.  (See comments above the directory_name member of
+	 * struct merged_info for why we can use pointer comparison instead of
+	 * strcmp here.)
+	 */
+	if (new_directory_name == info->last_directory)
+		return 0;
+
+	/*
+	 * If we are just starting (last_directory is NULL), or last_directory
+	 * is a prefix of the current directory, then we can just update
+	 * info->offsets to record the offset where we started this directory
+	 * and update last_directory to have quick access to it.
+	 */
+	if (info->last_directory == NULL ||
+	    !strncmp(new_directory_name, info->last_directory,
+		     info->last_directory_len)) {
+		uintptr_t offset = info->versions.nr;
+
+		info->last_directory = new_directory_name;
+		info->last_directory_len = strlen(info->last_directory);
+		/*
+		 * Record the offset into info->versions where we will
+		 * start recording basenames of paths found within
+		 * new_directory_name.
+		 */
+		string_list_append(&info->offsets,
+				   info->last_directory)->util = (void*)offset;
+		return 0;
+	}
+
+	/*
+	 * The next entry that will be processed will be within
+	 * new_directory_name.  Since at this point we know that
+	 * new_directory_name is within a different directory than
+	 * info->last_directory, we have all entries for info->last_directory
+	 * in info->versions and we need to create a tree object for them.
+	 */
+	dir_info = strmap_get(&opt->priv->paths, info->last_directory);
+	assert(dir_info);
+	offset = (uintptr_t)info->offsets.items[info->offsets.nr-1].util;
+	if (offset == info->versions.nr) {
+		/*
+		 * Actually, we don't need to create a tree object in this
+		 * case.  Whenever all files within a directory disappear
+		 * during the merge (e.g. unmodified on one side and
+		 * deleted on the other, or files were renamed elsewhere),
+		 * then we get here and the directory itself needs to be
+		 * omitted from its parent tree as well.
+		 */
+		dir_info->is_null = 1;
+	} else {
+		/*
+		 * Write out the tree to the git object directory, and also
+		 * record the mode and oid in dir_info->result.
+		 */
+		dir_info->is_null = 0;
+		dir_info->result.mode = S_IFDIR;
+		if (write_tree(&dir_info->result.oid, &info->versions, offset,
+			       opt->repo->hash_algo->rawsz) < 0)
+			ret = -1;
+	}
+
+	/*
+	 * We've now used several entries from info->versions and one entry
+	 * from info->offsets, so we get rid of those values.
+	 */
+	info->offsets.nr--;
+	info->versions.nr = offset;
+
+	/*
+	 * Now we've taken care of the completed directory, but we need to
+	 * prepare things since future entries will be in
+	 * new_directory_name.  (In particular, process_entry() will be
+	 * appending new entries to info->versions.)  So, we need to make
+	 * sure new_directory_name is the last entry in info->offsets.
+	 */
+	prev_dir = info->offsets.nr == 0 ? NULL :
+		   info->offsets.items[info->offsets.nr-1].string;
+	if (new_directory_name != prev_dir) {
+		uintptr_t c = info->versions.nr;
+		string_list_append(&info->offsets,
+				   new_directory_name)->util = (void*)c;
+	}
+
+	/* And, of course, we need to update last_directory to match. */
+	info->last_directory = new_directory_name;
+	info->last_directory_len = strlen(info->last_directory);
+
+	return ret;
+}
+
+/* Per entry merge function */
+static int process_entry(struct merge_options *opt,
+			 const char *path,
+			 struct conflict_info *ci,
+			 struct directory_versions *dir_metadata)
+{
+	int df_file_index = 0;
+
+	VERIFY_CI(ci);
+	assert(ci->filemask >= 0 && ci->filemask <= 7);
+	/* ci->match_mask == 7 was handled in collect_merge_info_callback() */
+	assert(ci->match_mask == 0 || ci->match_mask == 3 ||
+	       ci->match_mask == 5 || ci->match_mask == 6);
+
+	if (ci->dirmask) {
+		record_entry_for_tree(dir_metadata, path, &ci->merged);
+		if (ci->filemask == 0)
+			/* nothing else to handle */
+			return 0;
+		assert(ci->df_conflict);
+	}
+
+	if (ci->df_conflict && ci->merged.result.mode == 0) {
+		int i;
+
+		/*
+		 * directory no longer in the way, but we do have a file we
+		 * need to place here so we need to clean away the "directory
+		 * merges to nothing" result.
+		 */
+		ci->df_conflict = 0;
+		assert(ci->filemask != 0);
+		ci->merged.clean = 0;
+		ci->merged.is_null = 0;
+		/* and we want to zero out any directory-related entries */
+		ci->match_mask = (ci->match_mask & ~ci->dirmask);
+		ci->dirmask = 0;
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			if (ci->filemask & (1 << i))
+				continue;
+			ci->stages[i].mode = 0;
+			oidcpy(&ci->stages[i].oid, null_oid());
+		}
+	} else if (ci->df_conflict && ci->merged.result.mode != 0) {
+		/*
+		 * This started out as a D/F conflict, and the entries in
+		 * the competing directory were not removed by the merge as
+		 * evidenced by write_completed_directory() writing a value
+		 * to ci->merged.result.mode.
+		 */
+		struct conflict_info *new_ci;
+		const char *branch;
+		const char *old_path = path;
+		int i;
+
+		assert(ci->merged.result.mode == S_IFDIR);
+
+		/*
+		 * If filemask is 1, we can just ignore the file as having
+		 * been deleted on both sides.  We do not want to overwrite
+		 * ci->merged.result, since it stores the tree for all the
+		 * files under it.
+		 */
+		if (ci->filemask == 1) {
+			ci->filemask = 0;
+			return 0;
+		}
+
+		/*
+		 * This file still exists on at least one side, and we want
+		 * the directory to remain here, so we need to move this
+		 * path to some new location.
+		 */
+		new_ci = mem_pool_calloc(&opt->priv->pool, 1, sizeof(*new_ci));
+
+		/* We don't really want new_ci->merged.result copied, but it'll
+		 * be overwritten below so it doesn't matter.  We also don't
+		 * want any directory mode/oid values copied, but we'll zero
+		 * those out immediately.  We do want the rest of ci copied.
+		 */
+		memcpy(new_ci, ci, sizeof(*ci));
+		new_ci->match_mask = (new_ci->match_mask & ~new_ci->dirmask);
+		new_ci->dirmask = 0;
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			if (new_ci->filemask & (1 << i))
+				continue;
+			/* zero out any entries related to directories */
+			new_ci->stages[i].mode = 0;
+			oidcpy(&new_ci->stages[i].oid, null_oid());
+		}
+
+		/*
+		 * Find out which side this file came from; note that we
+		 * cannot just use ci->filemask, because renames could cause
+		 * the filemask to go back to 7.  So we use dirmask, then
+		 * pick the opposite side's index.
+		 */
+		df_file_index = (ci->dirmask & (1 << 1)) ? 2 : 1;
+		branch = (df_file_index == 1) ? opt->branch1 : opt->branch2;
+		path = unique_path(opt, path, branch);
+		strmap_put(&opt->priv->paths, path, new_ci);
+
+		path_msg(opt, CONFLICT_FILE_DIRECTORY, 0,
+			 path, old_path, NULL, NULL,
+			 _("CONFLICT (file/directory): directory in the way "
+			   "of %s from %s; moving it to %s instead."),
+			 old_path, branch, path);
+
+		/*
+		 * Zero out the filemask for the old ci.  At this point, ci
+		 * was just an entry for a directory, so we don't need to
+		 * do anything more with it.
+		 */
+		ci->filemask = 0;
+
+		/*
+		 * Now note that we're working on the new entry (path was
+		 * updated above.
+		 */
+		ci = new_ci;
+	}
+
+	/*
+	 * NOTE: Below there is a long switch-like if-elseif-elseif... block
+	 *       which the code goes through even for the df_conflict cases
+	 *       above.
+	 */
+	if (ci->match_mask) {
+		ci->merged.clean = !ci->df_conflict && !ci->path_conflict;
+		if (ci->match_mask == 6) {
+			/* stages[1] == stages[2] */
+			ci->merged.result.mode = ci->stages[1].mode;
+			oidcpy(&ci->merged.result.oid, &ci->stages[1].oid);
+		} else {
+			/* determine the mask of the side that didn't match */
+			unsigned int othermask = 7 & ~ci->match_mask;
+			int side = (othermask == 4) ? 2 : 1;
+
+			ci->merged.result.mode = ci->stages[side].mode;
+			ci->merged.is_null = !ci->merged.result.mode;
+			if (ci->merged.is_null)
+				ci->merged.clean = 1;
+			oidcpy(&ci->merged.result.oid, &ci->stages[side].oid);
+
+			assert(othermask == 2 || othermask == 4);
+			assert(ci->merged.is_null ==
+			       (ci->filemask == ci->match_mask));
+		}
+	} else if (ci->filemask >= 6 &&
+		   (S_IFMT & ci->stages[1].mode) !=
+		   (S_IFMT & ci->stages[2].mode)) {
+		/* Two different items from (file/submodule/symlink) */
+		if (opt->priv->call_depth) {
+			/* Just use the version from the merge base */
+			ci->merged.clean = 0;
+			oidcpy(&ci->merged.result.oid, &ci->stages[0].oid);
+			ci->merged.result.mode = ci->stages[0].mode;
+			ci->merged.is_null = (ci->merged.result.mode == 0);
+		} else {
+			/* Handle by renaming one or both to separate paths. */
+			unsigned o_mode = ci->stages[0].mode;
+			unsigned a_mode = ci->stages[1].mode;
+			unsigned b_mode = ci->stages[2].mode;
+			struct conflict_info *new_ci;
+			const char *a_path = NULL, *b_path = NULL;
+			int rename_a = 0, rename_b = 0;
+
+			new_ci = mem_pool_alloc(&opt->priv->pool,
+						sizeof(*new_ci));
+
+			if (S_ISREG(a_mode))
+				rename_a = 1;
+			else if (S_ISREG(b_mode))
+				rename_b = 1;
+			else {
+				rename_a = 1;
+				rename_b = 1;
+			}
+
+			if (rename_a)
+				a_path = unique_path(opt, path, opt->branch1);
+			if (rename_b)
+				b_path = unique_path(opt, path, opt->branch2);
+
+			if (rename_a && rename_b) {
+				path_msg(opt, CONFLICT_DISTINCT_MODES, 0,
+					 path, a_path, b_path, NULL,
+					 _("CONFLICT (distinct types): %s had "
+					   "different types on each side; "
+					   "renamed both of them so each can "
+					   "be recorded somewhere."),
+					 path);
+			} else {
+				path_msg(opt, CONFLICT_DISTINCT_MODES, 0,
+					 path, rename_a ? a_path : b_path,
+					 NULL, NULL,
+					 _("CONFLICT (distinct types): %s had "
+					   "different types on each side; "
+					   "renamed one of them so each can be "
+					   "recorded somewhere."),
+					 path);
+			}
+
+			ci->merged.clean = 0;
+			memcpy(new_ci, ci, sizeof(*new_ci));
+
+			/* Put b into new_ci, removing a from stages */
+			new_ci->merged.result.mode = ci->stages[2].mode;
+			oidcpy(&new_ci->merged.result.oid, &ci->stages[2].oid);
+			new_ci->stages[1].mode = 0;
+			oidcpy(&new_ci->stages[1].oid, null_oid());
+			new_ci->filemask = 5;
+			if ((S_IFMT & b_mode) != (S_IFMT & o_mode)) {
+				new_ci->stages[0].mode = 0;
+				oidcpy(&new_ci->stages[0].oid, null_oid());
+				new_ci->filemask = 4;
+			}
+
+			/* Leave only a in ci, fixing stages. */
+			ci->merged.result.mode = ci->stages[1].mode;
+			oidcpy(&ci->merged.result.oid, &ci->stages[1].oid);
+			ci->stages[2].mode = 0;
+			oidcpy(&ci->stages[2].oid, null_oid());
+			ci->filemask = 3;
+			if ((S_IFMT & a_mode) != (S_IFMT & o_mode)) {
+				ci->stages[0].mode = 0;
+				oidcpy(&ci->stages[0].oid, null_oid());
+				ci->filemask = 2;
+			}
+
+			/* Insert entries into opt->priv_paths */
+			assert(rename_a || rename_b);
+			if (rename_a)
+				strmap_put(&opt->priv->paths, a_path, ci);
+
+			if (!rename_b)
+				b_path = path;
+			strmap_put(&opt->priv->paths, b_path, new_ci);
+
+			if (rename_a && rename_b)
+				strmap_remove(&opt->priv->paths, path, 0);
+
+			/*
+			 * Do special handling for b_path since process_entry()
+			 * won't be called on it specially.
+			 */
+			strmap_put(&opt->priv->conflicted, b_path, new_ci);
+			record_entry_for_tree(dir_metadata, b_path,
+					      &new_ci->merged);
+
+			/*
+			 * Remaining code for processing this entry should
+			 * think in terms of processing a_path.
+			 */
+			if (a_path)
+				path = a_path;
+		}
+	} else if (ci->filemask >= 6) {
+		/* Need a two-way or three-way content merge */
+		struct version_info merged_file;
+		int clean_merge;
+		struct version_info *o = &ci->stages[0];
+		struct version_info *a = &ci->stages[1];
+		struct version_info *b = &ci->stages[2];
+
+		clean_merge = handle_content_merge(opt, path, o, a, b,
+						   ci->pathnames,
+						   opt->priv->call_depth * 2,
+						   &merged_file);
+		if (clean_merge < 0)
+			return -1;
+		ci->merged.clean = clean_merge &&
+				   !ci->df_conflict && !ci->path_conflict;
+		ci->merged.result.mode = merged_file.mode;
+		ci->merged.is_null = (merged_file.mode == 0);
+		oidcpy(&ci->merged.result.oid, &merged_file.oid);
+		if (clean_merge && ci->df_conflict) {
+			assert(df_file_index == 1 || df_file_index == 2);
+			ci->filemask = 1 << df_file_index;
+			ci->stages[df_file_index].mode = merged_file.mode;
+			oidcpy(&ci->stages[df_file_index].oid, &merged_file.oid);
+		}
+		if (!clean_merge) {
+			const char *reason = _("content");
+			if (ci->filemask == 6)
+				reason = _("add/add");
+			if (S_ISGITLINK(merged_file.mode))
+				reason = _("submodule");
+			path_msg(opt, CONFLICT_CONTENTS, 0,
+				 path, NULL, NULL, NULL,
+				 _("CONFLICT (%s): Merge conflict in %s"),
+				 reason, path);
+		}
+	} else if (ci->filemask == 3 || ci->filemask == 5) {
+		/* Modify/delete */
+		const char *modify_branch, *delete_branch;
+		int side = (ci->filemask == 5) ? 2 : 1;
+		int index = opt->priv->call_depth ? 0 : side;
+
+		ci->merged.result.mode = ci->stages[index].mode;
+		oidcpy(&ci->merged.result.oid, &ci->stages[index].oid);
+		ci->merged.clean = 0;
+
+		modify_branch = (side == 1) ? opt->branch1 : opt->branch2;
+		delete_branch = (side == 1) ? opt->branch2 : opt->branch1;
+
+		if (opt->renormalize &&
+		    blob_unchanged(opt, &ci->stages[0], &ci->stages[side],
+				   path)) {
+			if (!ci->path_conflict) {
+				/*
+				 * Blob unchanged after renormalization, so
+				 * there's no modify/delete conflict after all;
+				 * we can just remove the file.
+				 */
+				ci->merged.is_null = 1;
+				ci->merged.clean = 1;
+				 /*
+				  * file goes away => even if there was a
+				  * directory/file conflict there isn't one now.
+				  */
+				ci->df_conflict = 0;
+			} else {
+				/* rename/delete, so conflict remains */
+			}
+		} else if (ci->path_conflict &&
+			   oideq(&ci->stages[0].oid, &ci->stages[side].oid)) {
+			/*
+			 * This came from a rename/delete; no action to take,
+			 * but avoid printing "modify/delete" conflict notice
+			 * since the contents were not modified.
+			 */
+		} else {
+			path_msg(opt, CONFLICT_MODIFY_DELETE, 0,
+				 path, NULL, NULL, NULL,
+				 _("CONFLICT (modify/delete): %s deleted in %s "
+				   "and modified in %s.  Version %s of %s left "
+				   "in tree."),
+				 path, delete_branch, modify_branch,
+				 modify_branch, path);
+		}
+	} else if (ci->filemask == 2 || ci->filemask == 4) {
+		/* Added on one side */
+		int side = (ci->filemask == 4) ? 2 : 1;
+		ci->merged.result.mode = ci->stages[side].mode;
+		oidcpy(&ci->merged.result.oid, &ci->stages[side].oid);
+		ci->merged.clean = !ci->df_conflict && !ci->path_conflict;
+	} else if (ci->filemask == 1) {
+		/* Deleted on both sides */
+		ci->merged.is_null = 1;
+		ci->merged.result.mode = 0;
+		oidcpy(&ci->merged.result.oid, null_oid());
+		assert(!ci->df_conflict);
+		ci->merged.clean = !ci->path_conflict;
+	}
+
+	/*
+	 * If still conflicted, record it separately.  This allows us to later
+	 * iterate over just conflicted entries when updating the index instead
+	 * of iterating over all entries.
+	 */
+	if (!ci->merged.clean)
+		strmap_put(&opt->priv->conflicted, path, ci);
+
+	/* Record metadata for ci->merged in dir_metadata */
+	record_entry_for_tree(dir_metadata, path, &ci->merged);
+	return 0;
+}
+
+static void prefetch_for_content_merges(struct merge_options *opt,
+					struct string_list *plist)
+{
+	struct string_list_item *e;
+	struct oid_array to_fetch = OID_ARRAY_INIT;
+
+	if (opt->repo != the_repository || !has_promisor_remote())
+		return;
+
+	for (e = &plist->items[plist->nr-1]; e >= plist->items; --e) {
+		/* char *path = e->string; */
+		struct conflict_info *ci = e->util;
+		int i;
+
+		/* Ignore clean entries */
+		if (ci->merged.clean)
+			continue;
+
+		/* Ignore entries that don't need a content merge */
+		if (ci->match_mask || ci->filemask < 6 ||
+		    !S_ISREG(ci->stages[1].mode) ||
+		    !S_ISREG(ci->stages[2].mode) ||
+		    oideq(&ci->stages[1].oid, &ci->stages[2].oid))
+			continue;
+
+		/* Also don't need content merge if base matches either side */
+		if (ci->filemask == 7 &&
+		    S_ISREG(ci->stages[0].mode) &&
+		    (oideq(&ci->stages[0].oid, &ci->stages[1].oid) ||
+		     oideq(&ci->stages[0].oid, &ci->stages[2].oid)))
+			continue;
+
+		for (i = 0; i < 3; i++) {
+			unsigned side_mask = (1 << i);
+			struct version_info *vi = &ci->stages[i];
+
+			if ((ci->filemask & side_mask) &&
+			    S_ISREG(vi->mode) &&
+			    oid_object_info_extended(opt->repo, &vi->oid, NULL,
+						     OBJECT_INFO_FOR_PREFETCH))
+				oid_array_append(&to_fetch, &vi->oid);
+		}
+	}
+
+	promisor_remote_get_direct(opt->repo, to_fetch.oid, to_fetch.nr);
+	oid_array_clear(&to_fetch);
+}
+
+static int process_entries(struct merge_options *opt,
+			   struct object_id *result_oid)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *e;
+	struct string_list plist = STRING_LIST_INIT_NODUP;
+	struct string_list_item *entry;
+	struct directory_versions dir_metadata = { STRING_LIST_INIT_NODUP,
+						   STRING_LIST_INIT_NODUP,
+						   NULL, 0 };
+	int ret = 0;
+
+	trace2_region_enter("merge", "process_entries setup", opt->repo);
+	if (strmap_empty(&opt->priv->paths)) {
+		oidcpy(result_oid, opt->repo->hash_algo->empty_tree);
+		return 0;
+	}
+
+	/* Hack to pre-allocate plist to the desired size */
+	trace2_region_enter("merge", "plist grow", opt->repo);
+	ALLOC_GROW(plist.items, strmap_get_size(&opt->priv->paths), plist.alloc);
+	trace2_region_leave("merge", "plist grow", opt->repo);
+
+	/* Put every entry from paths into plist, then sort */
+	trace2_region_enter("merge", "plist copy", opt->repo);
+	strmap_for_each_entry(&opt->priv->paths, &iter, e) {
+		string_list_append(&plist, e->key)->util = e->value;
+	}
+	trace2_region_leave("merge", "plist copy", opt->repo);
+
+	trace2_region_enter("merge", "plist special sort", opt->repo);
+	plist.cmp = sort_dirs_next_to_their_children;
+	string_list_sort(&plist);
+	trace2_region_leave("merge", "plist special sort", opt->repo);
+
+	trace2_region_leave("merge", "process_entries setup", opt->repo);
+
+	/*
+	 * Iterate over the items in reverse order, so we can handle paths
+	 * below a directory before needing to handle the directory itself.
+	 *
+	 * This allows us to write subtrees before we need to write trees,
+	 * and it also enables sane handling of directory/file conflicts
+	 * (because it allows us to know whether the directory is still in
+	 * the way when it is time to process the file at the same path).
+	 */
+	trace2_region_enter("merge", "processing", opt->repo);
+	prefetch_for_content_merges(opt, &plist);
+	for (entry = &plist.items[plist.nr-1]; entry >= plist.items; --entry) {
+		char *path = entry->string;
+		/*
+		 * NOTE: mi may actually be a pointer to a conflict_info, but
+		 * we have to check mi->clean first to see if it's safe to
+		 * reassign to such a pointer type.
+		 */
+		struct merged_info *mi = entry->util;
+
+		if (write_completed_directory(opt, mi->directory_name,
+					      &dir_metadata) < 0) {
+			ret = -1;
+			goto cleanup;
+		}
+		if (mi->clean)
+			record_entry_for_tree(&dir_metadata, path, mi);
+		else {
+			struct conflict_info *ci = (struct conflict_info *)mi;
+			if (process_entry(opt, path, ci, &dir_metadata) < 0) {
+				ret = -1;
+				goto cleanup;
+			};
+		}
+	}
+	trace2_region_leave("merge", "processing", opt->repo);
+
+	trace2_region_enter("merge", "process_entries cleanup", opt->repo);
+	if (dir_metadata.offsets.nr != 1 ||
+	    (uintptr_t)dir_metadata.offsets.items[0].util != 0) {
+		printf("dir_metadata.offsets.nr = %"PRIuMAX" (should be 1)\n",
+		       (uintmax_t)dir_metadata.offsets.nr);
+		printf("dir_metadata.offsets.items[0].util = %u (should be 0)\n",
+		       (unsigned)(uintptr_t)dir_metadata.offsets.items[0].util);
+		fflush(stdout);
+		BUG("dir_metadata accounting completely off; shouldn't happen");
+	}
+	if (write_tree(result_oid, &dir_metadata.versions, 0,
+		       opt->repo->hash_algo->rawsz) < 0)
+		ret = -1;
+cleanup:
+	string_list_clear(&plist, 0);
+	string_list_clear(&dir_metadata.versions, 0);
+	string_list_clear(&dir_metadata.offsets, 0);
+	trace2_region_leave("merge", "process_entries cleanup", opt->repo);
+
+	return ret;
+}
+
+/*** Function Grouping: functions related to merge_switch_to_result() ***/
+
+static int checkout(struct merge_options *opt,
+		    struct tree *prev,
+		    struct tree *next)
+{
+	/* Switch the index/working copy from old to new */
+	int ret;
+	struct tree_desc trees[2];
+	struct unpack_trees_options unpack_opts;
+
+	memset(&unpack_opts, 0, sizeof(unpack_opts));
+	unpack_opts.head_idx = -1;
+	unpack_opts.src_index = opt->repo->index;
+	unpack_opts.dst_index = opt->repo->index;
+
+	setup_unpack_trees_porcelain(&unpack_opts, "merge");
+
+	/*
+	 * NOTE: if this were just "git checkout" code, we would probably
+	 * read or refresh the cache and check for a conflicted index, but
+	 * builtin/merge.c or sequencer.c really needs to read the index
+	 * and check for conflicted entries before starting merging for a
+	 * good user experience (no sense waiting for merges/rebases before
+	 * erroring out), so there's no reason to duplicate that work here.
+	 */
+
+	/* 2-way merge to the new branch */
+	unpack_opts.update = 1;
+	unpack_opts.merge = 1;
+	unpack_opts.quiet = 0; /* FIXME: sequencer might want quiet? */
+	unpack_opts.verbose_update = (opt->verbosity > 2);
+	unpack_opts.fn = twoway_merge;
+	unpack_opts.preserve_ignored = 0; /* FIXME: !opts->overwrite_ignore */
+	parse_tree(prev);
+	init_tree_desc(&trees[0], prev->buffer, prev->size);
+	parse_tree(next);
+	init_tree_desc(&trees[1], next->buffer, next->size);
+
+	ret = unpack_trees(2, trees, &unpack_opts);
+	clear_unpack_trees_porcelain(&unpack_opts);
+	return ret;
+}
+
+static int record_conflicted_index_entries(struct merge_options *opt)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *e;
+	struct index_state *index = opt->repo->index;
+	struct checkout state = CHECKOUT_INIT;
+	int errs = 0;
+	int original_cache_nr;
+
+	if (strmap_empty(&opt->priv->conflicted))
+		return 0;
+
+	/*
+	 * We are in a conflicted state. These conflicts might be inside
+	 * sparse-directory entries, so check if any entries are outside
+	 * of the sparse-checkout cone preemptively.
+	 *
+	 * We set original_cache_nr below, but that might change if
+	 * index_name_pos() calls ask for paths within sparse directories.
+	 */
+	strmap_for_each_entry(&opt->priv->conflicted, &iter, e) {
+		if (!path_in_sparse_checkout(e->key, index)) {
+			ensure_full_index(index);
+			break;
+		}
+	}
+
+	/* If any entries have skip_worktree set, we'll have to check 'em out */
+	state.force = 1;
+	state.quiet = 1;
+	state.refresh_cache = 1;
+	state.istate = index;
+	original_cache_nr = index->cache_nr;
+
+	/* Append every entry from conflicted into index, then sort */
+	strmap_for_each_entry(&opt->priv->conflicted, &iter, e) {
+		const char *path = e->key;
+		struct conflict_info *ci = e->value;
+		int pos;
+		struct cache_entry *ce;
+		int i;
+
+		VERIFY_CI(ci);
+
+		/*
+		 * The index will already have a stage=0 entry for this path,
+		 * because we created an as-merged-as-possible version of the
+		 * file and checkout() moved the working copy and index over
+		 * to that version.
+		 *
+		 * However, previous iterations through this loop will have
+		 * added unstaged entries to the end of the cache which
+		 * ignore the standard alphabetical ordering of cache
+		 * entries and break invariants needed for index_name_pos()
+		 * to work.  However, we know the entry we want is before
+		 * those appended cache entries, so do a temporary swap on
+		 * cache_nr to only look through entries of interest.
+		 */
+		SWAP(index->cache_nr, original_cache_nr);
+		pos = index_name_pos(index, path, strlen(path));
+		SWAP(index->cache_nr, original_cache_nr);
+		if (pos < 0) {
+			if (ci->filemask != 1)
+				BUG("Conflicted %s but nothing in basic working tree or index; this shouldn't happen", path);
+			cache_tree_invalidate_path(index, path);
+		} else {
+			ce = index->cache[pos];
+
+			/*
+			 * Clean paths with CE_SKIP_WORKTREE set will not be
+			 * written to the working tree by the unpack_trees()
+			 * call in checkout().  Our conflicted entries would
+			 * have appeared clean to that code since we ignored
+			 * the higher order stages.  Thus, we need override
+			 * the CE_SKIP_WORKTREE bit and manually write those
+			 * files to the working disk here.
+			 */
+			if (ce_skip_worktree(ce))
+				errs |= checkout_entry(ce, &state, NULL, NULL);
+
+			/*
+			 * Mark this cache entry for removal and instead add
+			 * new stage>0 entries corresponding to the
+			 * conflicts.  If there are many conflicted entries, we
+			 * want to avoid memmove'ing O(NM) entries by
+			 * inserting the new entries one at a time.  So,
+			 * instead, we just add the new cache entries to the
+			 * end (ignoring normal index requirements on sort
+			 * order) and sort the index once we're all done.
+			 */
+			ce->ce_flags |= CE_REMOVE;
+		}
+
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			struct version_info *vi;
+			if (!(ci->filemask & (1ul << i)))
+				continue;
+			vi = &ci->stages[i];
+			ce = make_cache_entry(index, vi->mode, &vi->oid,
+					      path, i+1, 0);
+			add_index_entry(index, ce, ADD_CACHE_JUST_APPEND);
+		}
+	}
+
+	/*
+	 * Remove the unused cache entries (and invalidate the relevant
+	 * cache-trees), then sort the index entries to get the conflicted
+	 * entries we added to the end into their right locations.
+	 */
+	remove_marked_cache_entries(index, 1);
+	/*
+	 * No need for STABLE_QSORT -- cmp_cache_name_compare sorts primarily
+	 * on filename and secondarily on stage, and (name, stage #) are a
+	 * unique tuple.
+	 */
+	QSORT(index->cache, index->cache_nr, cmp_cache_name_compare);
+
+	return errs;
+}
+
+static void print_submodule_conflict_suggestion(struct string_list *csub) {
+	struct string_list_item *item;
+	struct strbuf msg = STRBUF_INIT;
+	struct strbuf tmp = STRBUF_INIT;
+	struct strbuf subs = STRBUF_INIT;
+
+	if (!csub->nr)
+		return;
+
+	strbuf_add_separated_string_list(&subs, " ", csub);
+	for_each_string_list_item(item, csub) {
+		struct conflicted_submodule_item *util = item->util;
+
+		/*
+		 * NEEDSWORK: The steps to resolve these errors deserve a more
+		 * detailed explanation than what is currently printed below.
+		 */
+		if (util->flag == CONFLICT_SUBMODULE_NOT_INITIALIZED ||
+		    util->flag == CONFLICT_SUBMODULE_HISTORY_NOT_AVAILABLE)
+			continue;
+
+		/*
+		 * TRANSLATORS: This is a line of advice to resolve a merge
+		 * conflict in a submodule. The first argument is the submodule
+		 * name, and the second argument is the abbreviated id of the
+		 * commit that needs to be merged.  For example:
+		 *  - go to submodule (mysubmodule), and either merge commit abc1234"
+		 */
+		strbuf_addf(&tmp, _(" - go to submodule (%s), and either merge commit %s\n"
+				    "   or update to an existing commit which has merged those changes\n"),
+			    item->string, util->abbrev);
+	}
+
+	/*
+	 * TRANSLATORS: This is a detailed message for resolving submodule
+	 * conflicts.  The first argument is string containing one step per
+	 * submodule.  The second is a space-separated list of submodule names.
+	 */
+	strbuf_addf(&msg,
+		    _("Recursive merging with submodules currently only supports trivial cases.\n"
+		      "Please manually handle the merging of each conflicted submodule.\n"
+		      "This can be accomplished with the following steps:\n"
+		      "%s"
+		      " - come back to superproject and run:\n\n"
+		      "      git add %s\n\n"
+		      "   to record the above merge or update\n"
+		      " - resolve any other conflicts in the superproject\n"
+		      " - commit the resulting index in the superproject\n"),
+		    tmp.buf, subs.buf);
+
+	printf("%s", msg.buf);
+
+	strbuf_release(&subs);
+	strbuf_release(&tmp);
+	strbuf_release(&msg);
+}
+
+void merge_display_update_messages(struct merge_options *opt,
+				   int detailed,
+				   struct merge_result *result)
+{
+	struct merge_options_internal *opti = result->priv;
+	struct hashmap_iter iter;
+	struct strmap_entry *e;
+	struct string_list olist = STRING_LIST_INIT_NODUP;
+
+	if (opt->record_conflict_msgs_as_headers)
+		BUG("Either display conflict messages or record them as headers, not both");
+
+	trace2_region_enter("merge", "display messages", opt->repo);
+
+	/* Hack to pre-allocate olist to the desired size */
+	ALLOC_GROW(olist.items, strmap_get_size(&opti->conflicts),
+		   olist.alloc);
+
+	/* Put every entry from output into olist, then sort */
+	strmap_for_each_entry(&opti->conflicts, &iter, e) {
+		string_list_append(&olist, e->key)->util = e->value;
+	}
+	string_list_sort(&olist);
+
+	/* Iterate over the items, printing them */
+	for (int path_nr = 0; path_nr < olist.nr; ++path_nr) {
+		struct string_list *conflicts = olist.items[path_nr].util;
+		for (int i = 0; i < conflicts->nr; i++) {
+			struct logical_conflict_info *info =
+				conflicts->items[i].util;
+
+			if (detailed) {
+				printf("%lu", (unsigned long)info->paths.nr);
+				putchar('\0');
+				for (int n = 0; n < info->paths.nr; n++) {
+					fputs(info->paths.v[n], stdout);
+					putchar('\0');
+				}
+				fputs(type_short_descriptions[info->type],
+				      stdout);
+				putchar('\0');
+			}
+			puts(conflicts->items[i].string);
+			if (detailed)
+				putchar('\0');
+		}
+	}
+	string_list_clear(&olist, 0);
+
+	print_submodule_conflict_suggestion(&opti->conflicted_submodules);
+
+	/* Also include needed rename limit adjustment now */
+	diff_warn_rename_limit("merge.renamelimit",
+			       opti->renames.needed_limit, 0);
+
+	trace2_region_leave("merge", "display messages", opt->repo);
+}
+
+void merge_get_conflicted_files(struct merge_result *result,
+				struct string_list *conflicted_files)
+{
+	struct hashmap_iter iter;
+	struct strmap_entry *e;
+	struct merge_options_internal *opti = result->priv;
+
+	strmap_for_each_entry(&opti->conflicted, &iter, e) {
+		const char *path = e->key;
+		struct conflict_info *ci = e->value;
+		int i;
+
+		VERIFY_CI(ci);
+
+		for (i = MERGE_BASE; i <= MERGE_SIDE2; i++) {
+			struct stage_info *si;
+
+			if (!(ci->filemask & (1ul << i)))
+				continue;
+
+			si = xmalloc(sizeof(*si));
+			si->stage = i+1;
+			si->mode = ci->stages[i].mode;
+			oidcpy(&si->oid, &ci->stages[i].oid);
+			string_list_append(conflicted_files, path)->util = si;
+		}
+	}
+	/* string_list_sort() uses a stable sort, so we're good */
+	string_list_sort(conflicted_files);
+}
+
+void merge_switch_to_result(struct merge_options *opt,
+			    struct tree *head,
+			    struct merge_result *result,
+			    int update_worktree_and_index,
+			    int display_update_msgs)
+{
+	assert(opt->priv == NULL);
+	if (result->clean >= 0 && update_worktree_and_index) {
+		const char *filename;
+		FILE *fp;
+
+		trace2_region_enter("merge", "checkout", opt->repo);
+		if (checkout(opt, head, result->tree)) {
+			/* failure to function */
+			result->clean = -1;
+			merge_finalize(opt, result);
+			trace2_region_leave("merge", "checkout", opt->repo);
+			return;
+		}
+		trace2_region_leave("merge", "checkout", opt->repo);
+
+		trace2_region_enter("merge", "record_conflicted", opt->repo);
+		opt->priv = result->priv;
+		if (record_conflicted_index_entries(opt)) {
+			/* failure to function */
+			opt->priv = NULL;
+			result->clean = -1;
+			merge_finalize(opt, result);
+			trace2_region_leave("merge", "record_conflicted",
+					    opt->repo);
+			return;
+		}
+		opt->priv = NULL;
+		trace2_region_leave("merge", "record_conflicted", opt->repo);
+
+		trace2_region_enter("merge", "write_auto_merge", opt->repo);
+		filename = git_path_auto_merge(opt->repo);
+		fp = xfopen(filename, "w");
+		fprintf(fp, "%s\n", oid_to_hex(&result->tree->object.oid));
+		fclose(fp);
+		trace2_region_leave("merge", "write_auto_merge", opt->repo);
+	}
+	if (display_update_msgs)
+		merge_display_update_messages(opt, /* detailed */ 0, result);
+
+	merge_finalize(opt, result);
+}
+
+void merge_finalize(struct merge_options *opt,
+		    struct merge_result *result)
+{
+	struct merge_options_internal *opti = result->priv;
+
+	if (opt->renormalize)
+		git_attr_set_direction(GIT_ATTR_CHECKIN);
+	assert(opt->priv == NULL);
+
+	clear_or_reinit_internal_opts(opti, 0);
+	FREE_AND_NULL(opti);
+}
+
+/*** Function Grouping: helper functions for merge_incore_*() ***/
+
+static struct tree *shift_tree_object(struct repository *repo,
+				      struct tree *one, struct tree *two,
+				      const char *subtree_shift)
+{
+	struct object_id shifted;
+
+	if (!*subtree_shift) {
+		shift_tree(repo, &one->object.oid, &two->object.oid, &shifted, 0);
+	} else {
+		shift_tree_by(repo, &one->object.oid, &two->object.oid, &shifted,
+			      subtree_shift);
+	}
+	if (oideq(&two->object.oid, &shifted))
+		return two;
+	return lookup_tree(repo, &shifted);
+}
+
+static inline void set_commit_tree(struct commit *c, struct tree *t)
+{
+	c->maybe_tree = t;
+}
+
+static struct commit *make_virtual_commit(struct repository *repo,
+					  struct tree *tree,
+					  const char *comment)
+{
+	struct commit *commit = alloc_commit_node(repo);
+
+	set_merge_remote_desc(commit, comment, (struct object *)commit);
+	set_commit_tree(commit, tree);
+	commit->object.parsed = 1;
+	return commit;
+}
+
+static void merge_start(struct merge_options *opt, struct merge_result *result)
+{
+	struct rename_info *renames;
+	int i;
+	struct mem_pool *pool = NULL;
+
+	/* Sanity checks on opt */
+	trace2_region_enter("merge", "sanity checks", opt->repo);
+	assert(opt->repo);
+
+	assert(opt->branch1 && opt->branch2);
+
+	assert(opt->detect_directory_renames >= MERGE_DIRECTORY_RENAMES_NONE &&
+	       opt->detect_directory_renames <= MERGE_DIRECTORY_RENAMES_TRUE);
+	assert(opt->rename_limit >= -1);
+	assert(opt->rename_score >= 0 && opt->rename_score <= MAX_SCORE);
+	assert(opt->show_rename_progress >= 0 && opt->show_rename_progress <= 1);
+
+	assert(opt->xdl_opts >= 0);
+	assert(opt->recursive_variant >= MERGE_VARIANT_NORMAL &&
+	       opt->recursive_variant <= MERGE_VARIANT_THEIRS);
+
+	if (opt->msg_header_prefix)
+		assert(opt->record_conflict_msgs_as_headers);
+
+	/*
+	 * detect_renames, verbosity, buffer_output, and obuf are ignored
+	 * fields that were used by "recursive" rather than "ort" -- but
+	 * sanity check them anyway.
+	 */
+	assert(opt->detect_renames >= -1 &&
+	       opt->detect_renames <= DIFF_DETECT_COPY);
+	assert(opt->verbosity >= 0 && opt->verbosity <= 5);
+	assert(opt->buffer_output <= 2);
+	assert(opt->obuf.len == 0);
+
+	assert(opt->priv == NULL);
+	if (result->_properly_initialized != 0 &&
+	    result->_properly_initialized != RESULT_INITIALIZED)
+		BUG("struct merge_result passed to merge_incore_*recursive() must be zeroed or filled with values from a previous run");
+	assert(!!result->priv == !!result->_properly_initialized);
+	if (result->priv) {
+		opt->priv = result->priv;
+		result->priv = NULL;
+		/*
+		 * opt->priv non-NULL means we had results from a previous
+		 * run; do a few sanity checks that user didn't mess with
+		 * it in an obvious fashion.
+		 */
+		assert(opt->priv->call_depth == 0);
+		assert(!opt->priv->toplevel_dir ||
+		       0 == strlen(opt->priv->toplevel_dir));
+	}
+	trace2_region_leave("merge", "sanity checks", opt->repo);
+
+	/* Default to histogram diff.  Actually, just hardcode it...for now. */
+	opt->xdl_opts = DIFF_WITH_ALG(opt, HISTOGRAM_DIFF);
+
+	/* Handle attr direction stuff for renormalization */
+	if (opt->renormalize)
+		git_attr_set_direction(GIT_ATTR_CHECKOUT);
+
+	/* Initialization of opt->priv, our internal merge data */
+	trace2_region_enter("merge", "allocate/init", opt->repo);
+	if (opt->priv) {
+		clear_or_reinit_internal_opts(opt->priv, 1);
+		string_list_init_nodup(&opt->priv->conflicted_submodules);
+		trace2_region_leave("merge", "allocate/init", opt->repo);
+		return;
+	}
+	opt->priv = xcalloc(1, sizeof(*opt->priv));
+
+	/* Initialization of various renames fields */
+	renames = &opt->priv->renames;
+	mem_pool_init(&opt->priv->pool, 0);
+	pool = &opt->priv->pool;
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
+		strintmap_init_with_options(&renames->dirs_removed[i],
+					    NOT_RELEVANT, pool, 0);
+		strmap_init_with_options(&renames->dir_rename_count[i],
+					 NULL, 1);
+		strmap_init_with_options(&renames->dir_renames[i],
+					 NULL, 0);
+		/*
+		 * relevant_sources uses -1 for the default, because we need
+		 * to be able to distinguish not-in-strintmap from valid
+		 * relevant_source values from enum file_rename_relevance.
+		 * In particular, possibly_cache_new_pair() expects a negative
+		 * value for not-found entries.
+		 */
+		strintmap_init_with_options(&renames->relevant_sources[i],
+					    -1 /* explicitly invalid */,
+					    pool, 0);
+		strmap_init_with_options(&renames->cached_pairs[i],
+					 NULL, 1);
+		strset_init_with_options(&renames->cached_irrelevant[i],
+					 NULL, 1);
+		strset_init_with_options(&renames->cached_target_names[i],
+					 NULL, 0);
+	}
+	for (i = MERGE_SIDE1; i <= MERGE_SIDE2; i++) {
+		strintmap_init_with_options(&renames->deferred[i].possible_trivial_merges,
+					    0, pool, 0);
+		strset_init_with_options(&renames->deferred[i].target_dirs,
+					 pool, 1);
+		renames->deferred[i].trivial_merges_okay = 1; /* 1 == maybe */
+	}
+
+	/*
+	 * Although we initialize opt->priv->paths with strdup_strings=0,
+	 * that's just to avoid making yet another copy of an allocated
+	 * string.  Putting the entry into paths means we are taking
+	 * ownership, so we will later free it.
+	 *
+	 * In contrast, conflicted just has a subset of keys from paths, so
+	 * we don't want to free those (it'd be a duplicate free).
+	 */
+	strmap_init_with_options(&opt->priv->paths, pool, 0);
+	strmap_init_with_options(&opt->priv->conflicted, pool, 0);
+
+	/*
+	 * keys & string_lists in conflicts will sometimes need to outlive
+	 * "paths", so it will have a copy of relevant keys.  It's probably
+	 * a small subset of the overall paths that have special output.
+	 */
+	strmap_init(&opt->priv->conflicts);
+
+	trace2_region_leave("merge", "allocate/init", opt->repo);
+}
+
+static void merge_check_renames_reusable(struct merge_options *opt,
+					 struct merge_result *result,
+					 struct tree *merge_base,
+					 struct tree *side1,
+					 struct tree *side2)
+{
+	struct rename_info *renames;
+	struct tree **merge_trees;
+	struct merge_options_internal *opti = result->priv;
+
+	if (!opti)
+		return;
+
+	renames = &opti->renames;
+	merge_trees = renames->merge_trees;
+
+	/*
+	 * Handle case where previous merge operation did not want cache to
+	 * take effect, e.g. because rename/rename(1to1) makes it invalid.
+	 */
+	if (!merge_trees[0]) {
+		assert(!merge_trees[0] && !merge_trees[1] && !merge_trees[2]);
+		renames->cached_pairs_valid_side = 0; /* neither side valid */
+		return;
+	}
+
+	/*
+	 * Handle other cases; note that merge_trees[0..2] will only
+	 * be NULL if opti is, or if all three were manually set to
+	 * NULL by e.g. rename/rename(1to1) handling.
+	 */
+	assert(merge_trees[0] && merge_trees[1] && merge_trees[2]);
+
+	/* Check if we meet a condition for re-using cached_pairs */
+	if (oideq(&merge_base->object.oid, &merge_trees[2]->object.oid) &&
+	    oideq(&side1->object.oid, &result->tree->object.oid))
+		renames->cached_pairs_valid_side = MERGE_SIDE1;
+	else if (oideq(&merge_base->object.oid, &merge_trees[1]->object.oid) &&
+		 oideq(&side2->object.oid, &result->tree->object.oid))
+		renames->cached_pairs_valid_side = MERGE_SIDE2;
+	else
+		renames->cached_pairs_valid_side = 0; /* neither side valid */
+}
+
+/*** Function Grouping: merge_incore_*() and their internal variants ***/
+
+/*
+ * Originally from merge_trees_internal(); heavily adapted, though.
+ */
+static void merge_ort_nonrecursive_internal(struct merge_options *opt,
+					    struct tree *merge_base,
+					    struct tree *side1,
+					    struct tree *side2,
+					    struct merge_result *result)
+{
+	struct object_id working_tree_oid;
+
+	if (opt->subtree_shift) {
+		side2 = shift_tree_object(opt->repo, side1, side2,
+					  opt->subtree_shift);
+		merge_base = shift_tree_object(opt->repo, side1, merge_base,
+					       opt->subtree_shift);
+	}
+
+redo:
+	trace2_region_enter("merge", "collect_merge_info", opt->repo);
+	if (collect_merge_info(opt, merge_base, side1, side2) != 0) {
+		/*
+		 * TRANSLATORS: The %s arguments are: 1) tree hash of a merge
+		 * base, and 2-3) the trees for the two trees we're merging.
+		 */
+		err(opt, _("collecting merge info failed for trees %s, %s, %s"),
+		    oid_to_hex(&merge_base->object.oid),
+		    oid_to_hex(&side1->object.oid),
+		    oid_to_hex(&side2->object.oid));
+		result->clean = -1;
+		return;
+	}
+	trace2_region_leave("merge", "collect_merge_info", opt->repo);
+
+	trace2_region_enter("merge", "renames", opt->repo);
+	result->clean = detect_and_process_renames(opt, merge_base,
+						   side1, side2);
+	trace2_region_leave("merge", "renames", opt->repo);
+	if (opt->priv->renames.redo_after_renames == 2) {
+		trace2_region_enter("merge", "reset_maps", opt->repo);
+		clear_or_reinit_internal_opts(opt->priv, 1);
+		trace2_region_leave("merge", "reset_maps", opt->repo);
+		goto redo;
+	}
+
+	trace2_region_enter("merge", "process_entries", opt->repo);
+	if (process_entries(opt, &working_tree_oid) < 0)
+		result->clean = -1;
+	trace2_region_leave("merge", "process_entries", opt->repo);
+
+	/* Set return values */
+	result->path_messages = &opt->priv->conflicts;
+
+	if (result->clean >= 0) {
+		result->tree = parse_tree_indirect(&working_tree_oid);
+		/* existence of conflicted entries implies unclean */
+		result->clean &= strmap_empty(&opt->priv->conflicted);
+	}
+	if (!opt->priv->call_depth) {
+		result->priv = opt->priv;
+		result->_properly_initialized = RESULT_INITIALIZED;
+		opt->priv = NULL;
+	}
+}
+
+/*
+ * Originally from merge_recursive_internal(); somewhat adapted, though.
+ */
+static void merge_ort_internal(struct merge_options *opt,
+			       struct commit_list *merge_bases,
+			       struct commit *h1,
+			       struct commit *h2,
+			       struct merge_result *result)
+{
+	struct commit *next;
+	struct commit *merged_merge_bases;
+	const char *ancestor_name;
+	struct strbuf merge_base_abbrev = STRBUF_INIT;
+
+	if (!merge_bases) {
+		merge_bases = get_merge_bases(h1, h2);
+		/* See merge-ort.h:merge_incore_recursive() declaration NOTE */
+		merge_bases = reverse_commit_list(merge_bases);
+	}
+
+	merged_merge_bases = pop_commit(&merge_bases);
+	if (!merged_merge_bases) {
+		/* if there is no common ancestor, use an empty tree */
+		struct tree *tree;
+
+		tree = lookup_tree(opt->repo, opt->repo->hash_algo->empty_tree);
+		merged_merge_bases = make_virtual_commit(opt->repo, tree,
+							 "ancestor");
+		ancestor_name = "empty tree";
+	} else if (merge_bases) {
+		ancestor_name = "merged common ancestors";
+	} else {
+		strbuf_add_unique_abbrev(&merge_base_abbrev,
+					 &merged_merge_bases->object.oid,
+					 DEFAULT_ABBREV);
+		ancestor_name = merge_base_abbrev.buf;
+	}
+
+	for (next = pop_commit(&merge_bases); next;
+	     next = pop_commit(&merge_bases)) {
+		const char *saved_b1, *saved_b2;
+		struct commit *prev = merged_merge_bases;
+
+		opt->priv->call_depth++;
+		/*
+		 * When the merge fails, the result contains files
+		 * with conflict markers. The cleanness flag is
+		 * ignored (unless indicating an error), it was never
+		 * actually used, as result of merge_trees has always
+		 * overwritten it: the committed "conflicts" were
+		 * already resolved.
+		 */
+		saved_b1 = opt->branch1;
+		saved_b2 = opt->branch2;
+		opt->branch1 = "Temporary merge branch 1";
+		opt->branch2 = "Temporary merge branch 2";
+		merge_ort_internal(opt, NULL, prev, next, result);
+		if (result->clean < 0)
+			return;
+		opt->branch1 = saved_b1;
+		opt->branch2 = saved_b2;
+		opt->priv->call_depth--;
+
+		merged_merge_bases = make_virtual_commit(opt->repo,
+							 result->tree,
+							 "merged tree");
+		commit_list_insert(prev, &merged_merge_bases->parents);
+		commit_list_insert(next, &merged_merge_bases->parents->next);
+
+		clear_or_reinit_internal_opts(opt->priv, 1);
+	}
+
+	opt->ancestor = ancestor_name;
+	merge_ort_nonrecursive_internal(opt,
+					repo_get_commit_tree(opt->repo,
+							     merged_merge_bases),
+					repo_get_commit_tree(opt->repo, h1),
+					repo_get_commit_tree(opt->repo, h2),
+					result);
+	strbuf_release(&merge_base_abbrev);
+	opt->ancestor = NULL;  /* avoid accidental re-use of opt->ancestor */
+}
+
+void merge_incore_nonrecursive(struct merge_options *opt,
+			       struct tree *merge_base,
+			       struct tree *side1,
+			       struct tree *side2,
+			       struct merge_result *result)
+{
+	trace2_region_enter("merge", "incore_nonrecursive", opt->repo);
+
+	trace2_region_enter("merge", "merge_start", opt->repo);
+	assert(opt->ancestor != NULL);
+	merge_check_renames_reusable(opt, result, merge_base, side1, side2);
+	merge_start(opt, result);
+	/*
+	 * Record the trees used in this merge, so if there's a next merge in
+	 * a cherry-pick or rebase sequence it might be able to take advantage
+	 * of the cached_pairs in that next merge.
+	 */
+	opt->priv->renames.merge_trees[0] = merge_base;
+	opt->priv->renames.merge_trees[1] = side1;
+	opt->priv->renames.merge_trees[2] = side2;
+	trace2_region_leave("merge", "merge_start", opt->repo);
+
+	merge_ort_nonrecursive_internal(opt, merge_base, side1, side2, result);
+	trace2_region_leave("merge", "incore_nonrecursive", opt->repo);
+}
+
+void merge_incore_recursive(struct merge_options *opt,
+			    struct commit_list *merge_bases,
+			    struct commit *side1,
+			    struct commit *side2,
+			    struct merge_result *result)
+{
+	trace2_region_enter("merge", "incore_recursive", opt->repo);
+
+	/* We set the ancestor label based on the merge_bases */
+	assert(opt->ancestor == NULL);
+
+	trace2_region_enter("merge", "merge_start", opt->repo);
+	merge_start(opt, result);
+	trace2_region_leave("merge", "merge_start", opt->repo);
+
+	merge_ort_internal(opt, merge_bases, side1, side2, result);
+	trace2_region_leave("merge", "incore_recursive", opt->repo);
+}