Adding upstream version 1:2.30.2.upstream/1%2.30.2upstream

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

1 files changed, 1075 insertions, 0 deletions

diff --git a/builtin/pull.c b/builtin/pull.c
new file mode 100644
index 0000000..aa56ebc
--- /dev/null
+++ b/builtin/pull.c
@@ -0,0 +1,1075 @@
+/*
+ * Builtin "git pull"
+ *
+ * Based on git-pull.sh by Junio C Hamano
+ *
+ * Fetch one or more remote refs and merge it/them into the current HEAD.
+ */
+#define USE_THE_INDEX_COMPATIBILITY_MACROS
+#include "cache.h"
+#include "config.h"
+#include "builtin.h"
+#include "parse-options.h"
+#include "exec-cmd.h"
+#include "run-command.h"
+#include "oid-array.h"
+#include "remote.h"
+#include "dir.h"
+#include "rebase.h"
+#include "refs.h"
+#include "refspec.h"
+#include "revision.h"
+#include "submodule.h"
+#include "submodule-config.h"
+#include "tempfile.h"
+#include "lockfile.h"
+#include "wt-status.h"
+#include "commit-reach.h"
+#include "sequencer.h"
+
+/**
+ * Parses the value of --rebase. If value is a false value, returns
+ * REBASE_FALSE. If value is a true value, returns REBASE_TRUE. If value is
+ * "merges", returns REBASE_MERGES. If value is "preserve", returns
+ * REBASE_PRESERVE. If value is a invalid value, dies with a fatal error if
+ * fatal is true, otherwise returns REBASE_INVALID.
+ */
+static enum rebase_type parse_config_rebase(const char *key, const char *value,
+		int fatal)
+{
+	enum rebase_type v = rebase_parse_value(value);
+	if (v != REBASE_INVALID)
+		return v;
+
+	if (fatal)
+		die(_("Invalid value for %s: %s"), key, value);
+	else
+		error(_("Invalid value for %s: %s"), key, value);
+
+	return REBASE_INVALID;
+}
+
+/**
+ * Callback for --rebase, which parses arg with parse_config_rebase().
+ */
+static int parse_opt_rebase(const struct option *opt, const char *arg, int unset)
+{
+	enum rebase_type *value = opt->value;
+
+	if (arg)
+		*value = parse_config_rebase("--rebase", arg, 0);
+	else
+		*value = unset ? REBASE_FALSE : REBASE_TRUE;
+	return *value == REBASE_INVALID ? -1 : 0;
+}
+
+static const char * const pull_usage[] = {
+	N_("git pull [<options>] [<repository> [<refspec>...]]"),
+	NULL
+};
+
+/* Shared options */
+static int opt_verbosity;
+static char *opt_progress;
+static int recurse_submodules = RECURSE_SUBMODULES_DEFAULT;
+
+/* Options passed to git-merge or git-rebase */
+static enum rebase_type opt_rebase = -1;
+static char *opt_diffstat;
+static char *opt_log;
+static char *opt_signoff;
+static char *opt_squash;
+static char *opt_commit;
+static char *opt_edit;
+static char *cleanup_arg;
+static char *opt_ff;
+static char *opt_verify_signatures;
+static int opt_autostash = -1;
+static int config_autostash;
+static int check_trust_level = 1;
+static struct strvec opt_strategies = STRVEC_INIT;
+static struct strvec opt_strategy_opts = STRVEC_INIT;
+static char *opt_gpg_sign;
+static int opt_allow_unrelated_histories;
+
+/* Options passed to git-fetch */
+static char *opt_all;
+static char *opt_append;
+static char *opt_upload_pack;
+static int opt_force;
+static char *opt_tags;
+static char *opt_prune;
+static char *max_children;
+static int opt_dry_run;
+static char *opt_keep;
+static char *opt_depth;
+static char *opt_unshallow;
+static char *opt_update_shallow;
+static char *opt_refmap;
+static char *opt_ipv4;
+static char *opt_ipv6;
+static int opt_show_forced_updates = -1;
+static char *set_upstream;
+static struct strvec opt_fetch = STRVEC_INIT;
+
+static struct option pull_options[] = {
+	/* Shared options */
+	OPT__VERBOSITY(&opt_verbosity),
+	OPT_PASSTHRU(0, "progress", &opt_progress, NULL,
+		N_("force progress reporting"),
+		PARSE_OPT_NOARG),
+	OPT_CALLBACK_F(0, "recurse-submodules",
+		   &recurse_submodules, N_("on-demand"),
+		   N_("control for recursive fetching of submodules"),
+		   PARSE_OPT_OPTARG, option_fetch_parse_recurse_submodules),
+
+	/* Options passed to git-merge or git-rebase */
+	OPT_GROUP(N_("Options related to merging")),
+	OPT_CALLBACK_F('r', "rebase", &opt_rebase,
+	  "(false|true|merges|preserve|interactive)",
+	  N_("incorporate changes by rebasing rather than merging"),
+	  PARSE_OPT_OPTARG, parse_opt_rebase),
+	OPT_PASSTHRU('n', NULL, &opt_diffstat, NULL,
+		N_("do not show a diffstat at the end of the merge"),
+		PARSE_OPT_NOARG | PARSE_OPT_NONEG),
+	OPT_PASSTHRU(0, "stat", &opt_diffstat, NULL,
+		N_("show a diffstat at the end of the merge"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "summary", &opt_diffstat, NULL,
+		N_("(synonym to --stat)"),
+		PARSE_OPT_NOARG | PARSE_OPT_HIDDEN),
+	OPT_PASSTHRU(0, "log", &opt_log, N_("n"),
+		N_("add (at most <n>) entries from shortlog to merge commit message"),
+		PARSE_OPT_OPTARG),
+	OPT_PASSTHRU(0, "signoff", &opt_signoff, NULL,
+		N_("add a Signed-off-by trailer"),
+		PARSE_OPT_OPTARG),
+	OPT_PASSTHRU(0, "squash", &opt_squash, NULL,
+		N_("create a single commit instead of doing a merge"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "commit", &opt_commit, NULL,
+		N_("perform a commit if the merge succeeds (default)"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "edit", &opt_edit, NULL,
+		N_("edit message before committing"),
+		PARSE_OPT_NOARG),
+	OPT_CLEANUP(&cleanup_arg),
+	OPT_PASSTHRU(0, "ff", &opt_ff, NULL,
+		N_("allow fast-forward"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "ff-only", &opt_ff, NULL,
+		N_("abort if fast-forward is not possible"),
+		PARSE_OPT_NOARG | PARSE_OPT_NONEG),
+	OPT_PASSTHRU(0, "verify-signatures", &opt_verify_signatures, NULL,
+		N_("verify that the named commit has a valid GPG signature"),
+		PARSE_OPT_NOARG),
+	OPT_BOOL(0, "autostash", &opt_autostash,
+		N_("automatically stash/stash pop before and after")),
+	OPT_PASSTHRU_ARGV('s', "strategy", &opt_strategies, N_("strategy"),
+		N_("merge strategy to use"),
+		0),
+	OPT_PASSTHRU_ARGV('X', "strategy-option", &opt_strategy_opts,
+		N_("option=value"),
+		N_("option for selected merge strategy"),
+		0),
+	OPT_PASSTHRU('S', "gpg-sign", &opt_gpg_sign, N_("key-id"),
+		N_("GPG sign commit"),
+		PARSE_OPT_OPTARG),
+	OPT_SET_INT(0, "allow-unrelated-histories",
+		    &opt_allow_unrelated_histories,
+		    N_("allow merging unrelated histories"), 1),
+
+	/* Options passed to git-fetch */
+	OPT_GROUP(N_("Options related to fetching")),
+	OPT_PASSTHRU(0, "all", &opt_all, NULL,
+		N_("fetch from all remotes"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU('a', "append", &opt_append, NULL,
+		N_("append to .git/FETCH_HEAD instead of overwriting"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "upload-pack", &opt_upload_pack, N_("path"),
+		N_("path to upload pack on remote end"),
+		0),
+	OPT__FORCE(&opt_force, N_("force overwrite of local branch"), 0),
+	OPT_PASSTHRU('t', "tags", &opt_tags, NULL,
+		N_("fetch all tags and associated objects"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU('p', "prune", &opt_prune, NULL,
+		N_("prune remote-tracking branches no longer on remote"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU('j', "jobs", &max_children, N_("n"),
+		N_("number of submodules pulled in parallel"),
+		PARSE_OPT_OPTARG),
+	OPT_BOOL(0, "dry-run", &opt_dry_run,
+		N_("dry run")),
+	OPT_PASSTHRU('k', "keep", &opt_keep, NULL,
+		N_("keep downloaded pack"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "depth", &opt_depth, N_("depth"),
+		N_("deepen history of shallow clone"),
+		0),
+	OPT_PASSTHRU_ARGV(0, "shallow-since", &opt_fetch, N_("time"),
+		N_("deepen history of shallow repository based on time"),
+		0),
+	OPT_PASSTHRU_ARGV(0, "shallow-exclude", &opt_fetch, N_("revision"),
+		N_("deepen history of shallow clone, excluding rev"),
+		0),
+	OPT_PASSTHRU_ARGV(0, "deepen", &opt_fetch, N_("n"),
+		N_("deepen history of shallow clone"),
+		0),
+	OPT_PASSTHRU(0, "unshallow", &opt_unshallow, NULL,
+		N_("convert to a complete repository"),
+		PARSE_OPT_NONEG | PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "update-shallow", &opt_update_shallow, NULL,
+		N_("accept refs that update .git/shallow"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU(0, "refmap", &opt_refmap, N_("refmap"),
+		N_("specify fetch refmap"),
+		PARSE_OPT_NONEG),
+	OPT_PASSTHRU_ARGV('o', "server-option", &opt_fetch,
+		N_("server-specific"),
+		N_("option to transmit"),
+		0),
+	OPT_PASSTHRU('4',  "ipv4", &opt_ipv4, NULL,
+		N_("use IPv4 addresses only"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU('6',  "ipv6", &opt_ipv6, NULL,
+		N_("use IPv6 addresses only"),
+		PARSE_OPT_NOARG),
+	OPT_PASSTHRU_ARGV(0, "negotiation-tip", &opt_fetch, N_("revision"),
+		N_("report that we have only objects reachable from this object"),
+		0),
+	OPT_BOOL(0, "show-forced-updates", &opt_show_forced_updates,
+		 N_("check for forced-updates on all updated branches")),
+	OPT_PASSTHRU(0, "set-upstream", &set_upstream, NULL,
+		N_("set upstream for git pull/fetch"),
+		PARSE_OPT_NOARG),
+
+	OPT_END()
+};
+
+/**
+ * Pushes "-q" or "-v" switches into arr to match the opt_verbosity level.
+ */
+static void argv_push_verbosity(struct strvec *arr)
+{
+	int verbosity;
+
+	for (verbosity = opt_verbosity; verbosity > 0; verbosity--)
+		strvec_push(arr, "-v");
+
+	for (verbosity = opt_verbosity; verbosity < 0; verbosity++)
+		strvec_push(arr, "-q");
+}
+
+/**
+ * Pushes "-f" switches into arr to match the opt_force level.
+ */
+static void argv_push_force(struct strvec *arr)
+{
+	int force = opt_force;
+	while (force-- > 0)
+		strvec_push(arr, "-f");
+}
+
+/**
+ * Sets the GIT_REFLOG_ACTION environment variable to the concatenation of argv
+ */
+static void set_reflog_message(int argc, const char **argv)
+{
+	int i;
+	struct strbuf msg = STRBUF_INIT;
+
+	for (i = 0; i < argc; i++) {
+		if (i)
+			strbuf_addch(&msg, ' ');
+		strbuf_addstr(&msg, argv[i]);
+	}
+
+	setenv("GIT_REFLOG_ACTION", msg.buf, 0);
+
+	strbuf_release(&msg);
+}
+
+/**
+ * If pull.ff is unset, returns NULL. If pull.ff is "true", returns "--ff". If
+ * pull.ff is "false", returns "--no-ff". If pull.ff is "only", returns
+ * "--ff-only". Otherwise, if pull.ff is set to an invalid value, die with an
+ * error.
+ */
+static const char *config_get_ff(void)
+{
+	const char *value;
+
+	if (git_config_get_value("pull.ff", &value))
+		return NULL;
+
+	switch (git_parse_maybe_bool(value)) {
+	case 0:
+		return "--no-ff";
+	case 1:
+		return "--ff";
+	}
+
+	if (!strcmp(value, "only"))
+		return "--ff-only";
+
+	die(_("Invalid value for pull.ff: %s"), value);
+}
+
+/**
+ * Returns the default configured value for --rebase. It first looks for the
+ * value of "branch.$curr_branch.rebase", where $curr_branch is the current
+ * branch, and if HEAD is detached or the configuration key does not exist,
+ * looks for the value of "pull.rebase". If both configuration keys do not
+ * exist, returns REBASE_FALSE.
+ */
+static enum rebase_type config_get_rebase(void)
+{
+	struct branch *curr_branch = branch_get("HEAD");
+	const char *value;
+
+	if (curr_branch) {
+		char *key = xstrfmt("branch.%s.rebase", curr_branch->name);
+
+		if (!git_config_get_value(key, &value)) {
+			enum rebase_type ret = parse_config_rebase(key, value, 1);
+			free(key);
+			return ret;
+		}
+
+		free(key);
+	}
+
+	if (!git_config_get_value("pull.rebase", &value))
+		return parse_config_rebase("pull.rebase", value, 1);
+
+	if (opt_verbosity >= 0 && !opt_ff) {
+		advise(_("Pulling without specifying how to reconcile divergent branches is\n"
+			 "discouraged. You can squelch this message by running one of the following\n"
+			 "commands sometime before your next pull:\n"
+			 "\n"
+			 "  git config pull.rebase false  # merge (the default strategy)\n"
+			 "  git config pull.rebase true   # rebase\n"
+			 "  git config pull.ff only       # fast-forward only\n"
+			 "\n"
+			 "You can replace \"git config\" with \"git config --global\" to set a default\n"
+			 "preference for all repositories. You can also pass --rebase, --no-rebase,\n"
+			 "or --ff-only on the command line to override the configured default per\n"
+			 "invocation.\n"));
+	}
+
+	return REBASE_FALSE;
+}
+
+/**
+ * Read config variables.
+ */
+static int git_pull_config(const char *var, const char *value, void *cb)
+{
+	int status;
+
+	if (!strcmp(var, "rebase.autostash")) {
+		config_autostash = git_config_bool(var, value);
+		return 0;
+	} else if (!strcmp(var, "submodule.recurse")) {
+		recurse_submodules = git_config_bool(var, value) ?
+			RECURSE_SUBMODULES_ON : RECURSE_SUBMODULES_OFF;
+		return 0;
+	} else if (!strcmp(var, "gpg.mintrustlevel")) {
+		check_trust_level = 0;
+	}
+
+	status = git_gpg_config(var, value, cb);
+	if (status)
+		return status;
+
+	return git_default_config(var, value, cb);
+}
+
+/**
+ * Appends merge candidates from FETCH_HEAD that are not marked not-for-merge
+ * into merge_heads.
+ */
+static void get_merge_heads(struct oid_array *merge_heads)
+{
+	const char *filename = git_path_fetch_head(the_repository);
+	FILE *fp;
+	struct strbuf sb = STRBUF_INIT;
+	struct object_id oid;
+
+	fp = xfopen(filename, "r");
+	while (strbuf_getline_lf(&sb, fp) != EOF) {
+		const char *p;
+		if (parse_oid_hex(sb.buf, &oid, &p))
+			continue;  /* invalid line: does not start with object ID */
+		if (starts_with(p, "\tnot-for-merge\t"))
+			continue;  /* ref is not-for-merge */
+		oid_array_append(merge_heads, &oid);
+	}
+	fclose(fp);
+	strbuf_release(&sb);
+}
+
+/**
+ * Used by die_no_merge_candidates() as a for_each_remote() callback to
+ * retrieve the name of the remote if the repository only has one remote.
+ */
+static int get_only_remote(struct remote *remote, void *cb_data)
+{
+	const char **remote_name = cb_data;
+
+	if (*remote_name)
+		return -1;
+
+	*remote_name = remote->name;
+	return 0;
+}
+
+/**
+ * Dies with the appropriate reason for why there are no merge candidates:
+ *
+ * 1. We fetched from a specific remote, and a refspec was given, but it ended
+ *    up not fetching anything. This is usually because the user provided a
+ *    wildcard refspec which had no matches on the remote end.
+ *
+ * 2. We fetched from a non-default remote, but didn't specify a branch to
+ *    merge. We can't use the configured one because it applies to the default
+ *    remote, thus the user must specify the branches to merge.
+ *
+ * 3. We fetched from the branch's or repo's default remote, but:
+ *
+ *    a. We are not on a branch, so there will never be a configured branch to
+ *       merge with.
+ *
+ *    b. We are on a branch, but there is no configured branch to merge with.
+ *
+ * 4. We fetched from the branch's or repo's default remote, but the configured
+ *    branch to merge didn't get fetched. (Either it doesn't exist, or wasn't
+ *    part of the configured fetch refspec.)
+ */
+static void NORETURN die_no_merge_candidates(const char *repo, const char **refspecs)
+{
+	struct branch *curr_branch = branch_get("HEAD");
+	const char *remote = curr_branch ? curr_branch->remote_name : NULL;
+
+	if (*refspecs) {
+		if (opt_rebase)
+			fprintf_ln(stderr, _("There is no candidate for rebasing against among the refs that you just fetched."));
+		else
+			fprintf_ln(stderr, _("There are no candidates for merging among the refs that you just fetched."));
+		fprintf_ln(stderr, _("Generally this means that you provided a wildcard refspec which had no\n"
+					"matches on the remote end."));
+	} else if (repo && curr_branch && (!remote || strcmp(repo, remote))) {
+		fprintf_ln(stderr, _("You asked to pull from the remote '%s', but did not specify\n"
+			"a branch. Because this is not the default configured remote\n"
+			"for your current branch, you must specify a branch on the command line."),
+			repo);
+	} else if (!curr_branch) {
+		fprintf_ln(stderr, _("You are not currently on a branch."));
+		if (opt_rebase)
+			fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
+		else
+			fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
+		fprintf_ln(stderr, _("See git-pull(1) for details."));
+		fprintf(stderr, "\n");
+		fprintf_ln(stderr, "    git pull %s %s", _("<remote>"), _("<branch>"));
+		fprintf(stderr, "\n");
+	} else if (!curr_branch->merge_nr) {
+		const char *remote_name = NULL;
+
+		if (for_each_remote(get_only_remote, &remote_name) || !remote_name)
+			remote_name = _("<remote>");
+
+		fprintf_ln(stderr, _("There is no tracking information for the current branch."));
+		if (opt_rebase)
+			fprintf_ln(stderr, _("Please specify which branch you want to rebase against."));
+		else
+			fprintf_ln(stderr, _("Please specify which branch you want to merge with."));
+		fprintf_ln(stderr, _("See git-pull(1) for details."));
+		fprintf(stderr, "\n");
+		fprintf_ln(stderr, "    git pull %s %s", _("<remote>"), _("<branch>"));
+		fprintf(stderr, "\n");
+		fprintf_ln(stderr, _("If you wish to set tracking information for this branch you can do so with:"));
+		fprintf(stderr, "\n");
+		fprintf_ln(stderr, "    git branch --set-upstream-to=%s/%s %s\n",
+				remote_name, _("<branch>"), curr_branch->name);
+	} else
+		fprintf_ln(stderr, _("Your configuration specifies to merge with the ref '%s'\n"
+			"from the remote, but no such ref was fetched."),
+			*curr_branch->merge_name);
+	exit(1);
+}
+
+/**
+ * Parses argv into [<repo> [<refspecs>...]], returning their values in `repo`
+ * as a string and `refspecs` as a null-terminated array of strings. If `repo`
+ * is not provided in argv, it is set to NULL.
+ */
+static void parse_repo_refspecs(int argc, const char **argv, const char **repo,
+		const char ***refspecs)
+{
+	if (argc > 0) {
+		*repo = *argv++;
+		argc--;
+	} else
+		*repo = NULL;
+	*refspecs = argv;
+}
+
+/**
+ * Runs git-fetch, returning its exit status. `repo` and `refspecs` are the
+ * repository and refspecs to fetch, or NULL if they are not provided.
+ */
+static int run_fetch(const char *repo, const char **refspecs)
+{
+	struct strvec args = STRVEC_INIT;
+	int ret;
+
+	strvec_pushl(&args, "fetch", "--update-head-ok", NULL);
+
+	/* Shared options */
+	argv_push_verbosity(&args);
+	if (opt_progress)
+		strvec_push(&args, opt_progress);
+
+	/* Options passed to git-fetch */
+	if (opt_all)
+		strvec_push(&args, opt_all);
+	if (opt_append)
+		strvec_push(&args, opt_append);
+	if (opt_upload_pack)
+		strvec_push(&args, opt_upload_pack);
+	argv_push_force(&args);
+	if (opt_tags)
+		strvec_push(&args, opt_tags);
+	if (opt_prune)
+		strvec_push(&args, opt_prune);
+	if (recurse_submodules != RECURSE_SUBMODULES_DEFAULT)
+		switch (recurse_submodules) {
+		case RECURSE_SUBMODULES_ON:
+			strvec_push(&args, "--recurse-submodules=on");
+			break;
+		case RECURSE_SUBMODULES_OFF:
+			strvec_push(&args, "--recurse-submodules=no");
+			break;
+		case RECURSE_SUBMODULES_ON_DEMAND:
+			strvec_push(&args, "--recurse-submodules=on-demand");
+			break;
+		default:
+			BUG("submodule recursion option not understood");
+		}
+	if (max_children)
+		strvec_push(&args, max_children);
+	if (opt_dry_run)
+		strvec_push(&args, "--dry-run");
+	if (opt_keep)
+		strvec_push(&args, opt_keep);
+	if (opt_depth)
+		strvec_push(&args, opt_depth);
+	if (opt_unshallow)
+		strvec_push(&args, opt_unshallow);
+	if (opt_update_shallow)
+		strvec_push(&args, opt_update_shallow);
+	if (opt_refmap)
+		strvec_push(&args, opt_refmap);
+	if (opt_ipv4)
+		strvec_push(&args, opt_ipv4);
+	if (opt_ipv6)
+		strvec_push(&args, opt_ipv6);
+	if (opt_show_forced_updates > 0)
+		strvec_push(&args, "--show-forced-updates");
+	else if (opt_show_forced_updates == 0)
+		strvec_push(&args, "--no-show-forced-updates");
+	if (set_upstream)
+		strvec_push(&args, set_upstream);
+	strvec_pushv(&args, opt_fetch.v);
+
+	if (repo) {
+		strvec_push(&args, repo);
+		strvec_pushv(&args, refspecs);
+	} else if (*refspecs)
+		BUG("refspecs without repo?");
+	ret = run_command_v_opt(args.v, RUN_GIT_CMD);
+	strvec_clear(&args);
+	return ret;
+}
+
+/**
+ * "Pulls into void" by branching off merge_head.
+ */
+static int pull_into_void(const struct object_id *merge_head,
+		const struct object_id *curr_head)
+{
+	if (opt_verify_signatures) {
+		struct commit *commit;
+
+		commit = lookup_commit(the_repository, merge_head);
+		if (!commit)
+			die(_("unable to access commit %s"),
+			    oid_to_hex(merge_head));
+
+		verify_merge_signature(commit, opt_verbosity,
+				       check_trust_level);
+	}
+
+	/*
+	 * Two-way merge: we treat the index as based on an empty tree,
+	 * and try to fast-forward to HEAD. This ensures we will not lose
+	 * index/worktree changes that the user already made on the unborn
+	 * branch.
+	 */
+	if (checkout_fast_forward(the_repository,
+				  the_hash_algo->empty_tree,
+				  merge_head, 0))
+		return 1;
+
+	if (update_ref("initial pull", "HEAD", merge_head, curr_head, 0, UPDATE_REFS_DIE_ON_ERR))
+		return 1;
+
+	return 0;
+}
+
+static int rebase_submodules(void)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	cp.git_cmd = 1;
+	cp.no_stdin = 1;
+	strvec_pushl(&cp.args, "submodule", "update",
+		     "--recursive", "--rebase", NULL);
+	argv_push_verbosity(&cp.args);
+
+	return run_command(&cp);
+}
+
+static int update_submodules(void)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	cp.git_cmd = 1;
+	cp.no_stdin = 1;
+	strvec_pushl(&cp.args, "submodule", "update",
+		     "--recursive", "--checkout", NULL);
+	argv_push_verbosity(&cp.args);
+
+	return run_command(&cp);
+}
+
+/**
+ * Runs git-merge, returning its exit status.
+ */
+static int run_merge(void)
+{
+	int ret;
+	struct strvec args = STRVEC_INIT;
+
+	strvec_pushl(&args, "merge", NULL);
+
+	/* Shared options */
+	argv_push_verbosity(&args);
+	if (opt_progress)
+		strvec_push(&args, opt_progress);
+
+	/* Options passed to git-merge */
+	if (opt_diffstat)
+		strvec_push(&args, opt_diffstat);
+	if (opt_log)
+		strvec_push(&args, opt_log);
+	if (opt_signoff)
+		strvec_push(&args, opt_signoff);
+	if (opt_squash)
+		strvec_push(&args, opt_squash);
+	if (opt_commit)
+		strvec_push(&args, opt_commit);
+	if (opt_edit)
+		strvec_push(&args, opt_edit);
+	if (cleanup_arg)
+		strvec_pushf(&args, "--cleanup=%s", cleanup_arg);
+	if (opt_ff)
+		strvec_push(&args, opt_ff);
+	if (opt_verify_signatures)
+		strvec_push(&args, opt_verify_signatures);
+	strvec_pushv(&args, opt_strategies.v);
+	strvec_pushv(&args, opt_strategy_opts.v);
+	if (opt_gpg_sign)
+		strvec_push(&args, opt_gpg_sign);
+	if (opt_autostash == 0)
+		strvec_push(&args, "--no-autostash");
+	else if (opt_autostash == 1)
+		strvec_push(&args, "--autostash");
+	if (opt_allow_unrelated_histories > 0)
+		strvec_push(&args, "--allow-unrelated-histories");
+
+	strvec_push(&args, "FETCH_HEAD");
+	ret = run_command_v_opt(args.v, RUN_GIT_CMD);
+	strvec_clear(&args);
+	return ret;
+}
+
+/**
+ * Returns remote's upstream branch for the current branch. If remote is NULL,
+ * the current branch's configured default remote is used. Returns NULL if
+ * `remote` does not name a valid remote, HEAD does not point to a branch,
+ * remote is not the branch's configured remote or the branch does not have any
+ * configured upstream branch.
+ */
+static const char *get_upstream_branch(const char *remote)
+{
+	struct remote *rm;
+	struct branch *curr_branch;
+	const char *curr_branch_remote;
+
+	rm = remote_get(remote);
+	if (!rm)
+		return NULL;
+
+	curr_branch = branch_get("HEAD");
+	if (!curr_branch)
+		return NULL;
+
+	curr_branch_remote = remote_for_branch(curr_branch, NULL);
+	assert(curr_branch_remote);
+
+	if (strcmp(curr_branch_remote, rm->name))
+		return NULL;
+
+	return branch_get_upstream(curr_branch, NULL);
+}
+
+/**
+ * Derives the remote-tracking branch from the remote and refspec.
+ *
+ * FIXME: The current implementation assumes the default mapping of
+ * refs/heads/<branch_name> to refs/remotes/<remote_name>/<branch_name>.
+ */
+static const char *get_tracking_branch(const char *remote, const char *refspec)
+{
+	struct refspec_item spec;
+	const char *spec_src;
+	const char *merge_branch;
+
+	refspec_item_init_or_die(&spec, refspec, REFSPEC_FETCH);
+	spec_src = spec.src;
+	if (!*spec_src || !strcmp(spec_src, "HEAD"))
+		spec_src = "HEAD";
+	else if (skip_prefix(spec_src, "heads/", &spec_src))
+		;
+	else if (skip_prefix(spec_src, "refs/heads/", &spec_src))
+		;
+	else if (starts_with(spec_src, "refs/") ||
+		starts_with(spec_src, "tags/") ||
+		starts_with(spec_src, "remotes/"))
+		spec_src = "";
+
+	if (*spec_src) {
+		if (!strcmp(remote, "."))
+			merge_branch = mkpath("refs/heads/%s", spec_src);
+		else
+			merge_branch = mkpath("refs/remotes/%s/%s", remote, spec_src);
+	} else
+		merge_branch = NULL;
+
+	refspec_item_clear(&spec);
+	return merge_branch;
+}
+
+/**
+ * Given the repo and refspecs, sets fork_point to the point at which the
+ * current branch forked from its remote-tracking branch. Returns 0 on success,
+ * -1 on failure.
+ */
+static int get_rebase_fork_point(struct object_id *fork_point, const char *repo,
+		const char *refspec)
+{
+	int ret;
+	struct branch *curr_branch;
+	const char *remote_branch;
+	struct child_process cp = CHILD_PROCESS_INIT;
+	struct strbuf sb = STRBUF_INIT;
+
+	curr_branch = branch_get("HEAD");
+	if (!curr_branch)
+		return -1;
+
+	if (refspec)
+		remote_branch = get_tracking_branch(repo, refspec);
+	else
+		remote_branch = get_upstream_branch(repo);
+
+	if (!remote_branch)
+		return -1;
+
+	strvec_pushl(&cp.args, "merge-base", "--fork-point",
+		     remote_branch, curr_branch->name, NULL);
+	cp.no_stdin = 1;
+	cp.no_stderr = 1;
+	cp.git_cmd = 1;
+
+	ret = capture_command(&cp, &sb, GIT_MAX_HEXSZ);
+	if (ret)
+		goto cleanup;
+
+	ret = get_oid_hex(sb.buf, fork_point);
+	if (ret)
+		goto cleanup;
+
+cleanup:
+	strbuf_release(&sb);
+	return ret ? -1 : 0;
+}
+
+/**
+ * Sets merge_base to the octopus merge base of curr_head, merge_head and
+ * fork_point. Returns 0 if a merge base is found, 1 otherwise.
+ */
+static int get_octopus_merge_base(struct object_id *merge_base,
+		const struct object_id *curr_head,
+		const struct object_id *merge_head,
+		const struct object_id *fork_point)
+{
+	struct commit_list *revs = NULL, *result;
+
+	commit_list_insert(lookup_commit_reference(the_repository, curr_head),
+			   &revs);
+	commit_list_insert(lookup_commit_reference(the_repository, merge_head),
+			   &revs);
+	if (!is_null_oid(fork_point))
+		commit_list_insert(lookup_commit_reference(the_repository, fork_point),
+				   &revs);
+
+	result = get_octopus_merge_bases(revs);
+	free_commit_list(revs);
+	reduce_heads_replace(&result);
+
+	if (!result)
+		return 1;
+
+	oidcpy(merge_base, &result->item->object.oid);
+	free_commit_list(result);
+	return 0;
+}
+
+/**
+ * Given the current HEAD oid, the merge head returned from git-fetch and the
+ * fork point calculated by get_rebase_fork_point(), compute the <newbase> and
+ * <upstream> arguments to use for the upcoming git-rebase invocation.
+ */
+static int get_rebase_newbase_and_upstream(struct object_id *newbase,
+		struct object_id *upstream,
+		const struct object_id *curr_head,
+		const struct object_id *merge_head,
+		const struct object_id *fork_point)
+{
+	struct object_id oct_merge_base;
+
+	if (!get_octopus_merge_base(&oct_merge_base, curr_head, merge_head, fork_point))
+		if (!is_null_oid(fork_point) && oideq(&oct_merge_base, fork_point))
+			fork_point = NULL;
+
+	if (fork_point && !is_null_oid(fork_point))
+		oidcpy(upstream, fork_point);
+	else
+		oidcpy(upstream, merge_head);
+
+	oidcpy(newbase, merge_head);
+
+	return 0;
+}
+
+/**
+ * Given the <newbase> and <upstream> calculated by
+ * get_rebase_newbase_and_upstream(), runs git-rebase with the
+ * appropriate arguments and returns its exit status.
+ */
+static int run_rebase(const struct object_id *newbase,
+		const struct object_id *upstream)
+{
+	int ret;
+	struct strvec args = STRVEC_INIT;
+
+	strvec_push(&args, "rebase");
+
+	/* Shared options */
+	argv_push_verbosity(&args);
+
+	/* Options passed to git-rebase */
+	if (opt_rebase == REBASE_MERGES)
+		strvec_push(&args, "--rebase-merges");
+	else if (opt_rebase == REBASE_PRESERVE)
+		strvec_push(&args, "--preserve-merges");
+	else if (opt_rebase == REBASE_INTERACTIVE)
+		strvec_push(&args, "--interactive");
+	if (opt_diffstat)
+		strvec_push(&args, opt_diffstat);
+	strvec_pushv(&args, opt_strategies.v);
+	strvec_pushv(&args, opt_strategy_opts.v);
+	if (opt_gpg_sign)
+		strvec_push(&args, opt_gpg_sign);
+	if (opt_autostash == 0)
+		strvec_push(&args, "--no-autostash");
+	else if (opt_autostash == 1)
+		strvec_push(&args, "--autostash");
+	if (opt_verify_signatures &&
+	    !strcmp(opt_verify_signatures, "--verify-signatures"))
+		warning(_("ignoring --verify-signatures for rebase"));
+
+	strvec_push(&args, "--onto");
+	strvec_push(&args, oid_to_hex(newbase));
+
+	strvec_push(&args, oid_to_hex(upstream));
+
+	ret = run_command_v_opt(args.v, RUN_GIT_CMD);
+	strvec_clear(&args);
+	return ret;
+}
+
+int cmd_pull(int argc, const char **argv, const char *prefix)
+{
+	const char *repo, **refspecs;
+	struct oid_array merge_heads = OID_ARRAY_INIT;
+	struct object_id orig_head, curr_head;
+	struct object_id rebase_fork_point;
+	int autostash;
+
+	if (!getenv("GIT_REFLOG_ACTION"))
+		set_reflog_message(argc, argv);
+
+	git_config(git_pull_config, NULL);
+
+	argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);
+
+	if (cleanup_arg)
+		/*
+		 * this only checks the validity of cleanup_arg; we don't need
+		 * a valid value for use_editor
+		 */
+		get_cleanup_mode(cleanup_arg, 0);
+
+	parse_repo_refspecs(argc, argv, &repo, &refspecs);
+
+	if (!opt_ff)
+		opt_ff = xstrdup_or_null(config_get_ff());
+
+	if (opt_rebase < 0)
+		opt_rebase = config_get_rebase();
+
+	if (read_cache_unmerged())
+		die_resolve_conflict("pull");
+
+	if (file_exists(git_path_merge_head(the_repository)))
+		die_conclude_merge();
+
+	if (get_oid("HEAD", &orig_head))
+		oidclr(&orig_head);
+
+	autostash = config_autostash;
+	if (opt_rebase) {
+		if (opt_autostash != -1)
+			autostash = opt_autostash;
+
+		if (is_null_oid(&orig_head) && !is_cache_unborn())
+			die(_("Updating an unborn branch with changes added to the index."));
+
+		if (!autostash)
+			require_clean_work_tree(the_repository,
+				N_("pull with rebase"),
+				_("please commit or stash them."), 1, 0);
+
+		if (get_rebase_fork_point(&rebase_fork_point, repo, *refspecs))
+			oidclr(&rebase_fork_point);
+	}
+
+	if (run_fetch(repo, refspecs))
+		return 1;
+
+	if (opt_dry_run)
+		return 0;
+
+	if (get_oid("HEAD", &curr_head))
+		oidclr(&curr_head);
+
+	if (!is_null_oid(&orig_head) && !is_null_oid(&curr_head) &&
+			!oideq(&orig_head, &curr_head)) {
+		/*
+		 * The fetch involved updating the current branch.
+		 *
+		 * The working tree and the index file are still based on
+		 * orig_head commit, but we are merging into curr_head.
+		 * Update the working tree to match curr_head.
+		 */
+
+		warning(_("fetch updated the current branch head.\n"
+			"fast-forwarding your working tree from\n"
+			"commit %s."), oid_to_hex(&orig_head));
+
+		if (checkout_fast_forward(the_repository, &orig_head,
+					  &curr_head, 0))
+			die(_("Cannot fast-forward your working tree.\n"
+				"After making sure that you saved anything precious from\n"
+				"$ git diff %s\n"
+				"output, run\n"
+				"$ git reset --hard\n"
+				"to recover."), oid_to_hex(&orig_head));
+	}
+
+	get_merge_heads(&merge_heads);
+
+	if (!merge_heads.nr)
+		die_no_merge_candidates(repo, refspecs);
+
+	if (is_null_oid(&orig_head)) {
+		if (merge_heads.nr > 1)
+			die(_("Cannot merge multiple branches into empty head."));
+		return pull_into_void(merge_heads.oid, &curr_head);
+	}
+	if (opt_rebase && merge_heads.nr > 1)
+		die(_("Cannot rebase onto multiple branches."));
+
+	if (opt_rebase) {
+		int ret = 0;
+		int ran_ff = 0;
+
+		struct object_id newbase;
+		struct object_id upstream;
+		get_rebase_newbase_and_upstream(&newbase, &upstream, &curr_head,
+						merge_heads.oid, &rebase_fork_point);
+
+		if ((recurse_submodules == RECURSE_SUBMODULES_ON ||
+		     recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND) &&
+		    submodule_touches_in_range(the_repository, &upstream, &curr_head))
+			die(_("cannot rebase with locally recorded submodule modifications"));
+		if (!autostash) {
+			struct commit_list *list = NULL;
+			struct commit *merge_head, *head;
+
+			head = lookup_commit_reference(the_repository,
+						       &orig_head);
+			commit_list_insert(head, &list);
+			merge_head = lookup_commit_reference(the_repository,
+							     &merge_heads.oid[0]);
+			if (repo_is_descendant_of(the_repository,
+						  merge_head, list)) {
+				/* we can fast-forward this without invoking rebase */
+				opt_ff = "--ff-only";
+				ran_ff = 1;
+				ret = run_merge();
+			}
+			free_commit_list(list);
+		}
+		if (!ran_ff)
+			ret = run_rebase(&newbase, &upstream);
+
+		if (!ret && (recurse_submodules == RECURSE_SUBMODULES_ON ||
+			     recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND))
+			ret = rebase_submodules();
+
+		return ret;
+	} else {
+		int ret = run_merge();
+		if (!ret && (recurse_submodules == RECURSE_SUBMODULES_ON ||
+			     recurse_submodules == RECURSE_SUBMODULES_ON_DEMAND))
+			ret = update_submodules();
+		return ret;
+	}
+}