Adding upstream version 1:2.43.0.upstream/1%2.43.0

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

1 files changed, 1285 insertions, 0 deletions

diff --git a/attr.c b/attr.c
new file mode 100644
index 0000000..e62876d
--- /dev/null
+++ b/attr.c
@@ -0,0 +1,1285 @@
+/*
+ * Handle git attributes.  See gitattributes(5) for a description of
+ * the file syntax, and attr.h for a description of the API.
+ *
+ * One basic design decision here is that we are not going to support
+ * an insanely large number of attributes.
+ */
+
+#include "git-compat-util.h"
+#include "config.h"
+#include "environment.h"
+#include "exec-cmd.h"
+#include "attr.h"
+#include "dir.h"
+#include "gettext.h"
+#include "path.h"
+#include "utf8.h"
+#include "quote.h"
+#include "read-cache-ll.h"
+#include "revision.h"
+#include "object-store-ll.h"
+#include "setup.h"
+#include "thread-utils.h"
+#include "tree-walk.h"
+#include "object-name.h"
+
+const char *git_attr_tree;
+
+const char git_attr__true[] = "(builtin)true";
+const char git_attr__false[] = "\0(builtin)false";
+static const char git_attr__unknown[] = "(builtin)unknown";
+#define ATTR__TRUE git_attr__true
+#define ATTR__FALSE git_attr__false
+#define ATTR__UNSET NULL
+#define ATTR__UNKNOWN git_attr__unknown
+
+struct git_attr {
+	unsigned int attr_nr; /* unique attribute number */
+	char name[FLEX_ARRAY]; /* attribute name */
+};
+
+const char *git_attr_name(const struct git_attr *attr)
+{
+	return attr->name;
+}
+
+struct attr_hashmap {
+	struct hashmap map;
+	pthread_mutex_t mutex;
+};
+
+static inline void hashmap_lock(struct attr_hashmap *map)
+{
+	pthread_mutex_lock(&map->mutex);
+}
+
+static inline void hashmap_unlock(struct attr_hashmap *map)
+{
+	pthread_mutex_unlock(&map->mutex);
+}
+
+/* The container for objects stored in "struct attr_hashmap" */
+struct attr_hash_entry {
+	struct hashmap_entry ent;
+	const char *key; /* the key; memory should be owned by value */
+	size_t keylen; /* length of the key */
+	void *value; /* the stored value */
+};
+
+/* attr_hashmap comparison function */
+static int attr_hash_entry_cmp(const void *cmp_data UNUSED,
+			       const struct hashmap_entry *eptr,
+			       const struct hashmap_entry *entry_or_key,
+			       const void *keydata UNUSED)
+{
+	const struct attr_hash_entry *a, *b;
+
+	a = container_of(eptr, const struct attr_hash_entry, ent);
+	b = container_of(entry_or_key, const struct attr_hash_entry, ent);
+	return (a->keylen != b->keylen) || strncmp(a->key, b->key, a->keylen);
+}
+
+/*
+ * The global dictionary of all interned attributes.  This
+ * is a singleton object which is shared between threads.
+ * Access to this dictionary must be surrounded with a mutex.
+ */
+static struct attr_hashmap g_attr_hashmap = {
+	.map = HASHMAP_INIT(attr_hash_entry_cmp, NULL),
+};
+
+/*
+ * Retrieve the 'value' stored in a hashmap given the provided 'key'.
+ * If there is no matching entry, return NULL.
+ */
+static void *attr_hashmap_get(struct attr_hashmap *map,
+			      const char *key, size_t keylen)
+{
+	struct attr_hash_entry k;
+	struct attr_hash_entry *e;
+
+	hashmap_entry_init(&k.ent, memhash(key, keylen));
+	k.key = key;
+	k.keylen = keylen;
+	e = hashmap_get_entry(&map->map, &k, ent, NULL);
+
+	return e ? e->value : NULL;
+}
+
+/* Add 'value' to a hashmap based on the provided 'key'. */
+static void attr_hashmap_add(struct attr_hashmap *map,
+			     const char *key, size_t keylen,
+			     void *value)
+{
+	struct attr_hash_entry *e;
+
+	e = xmalloc(sizeof(struct attr_hash_entry));
+	hashmap_entry_init(&e->ent, memhash(key, keylen));
+	e->key = key;
+	e->keylen = keylen;
+	e->value = value;
+
+	hashmap_add(&map->map, &e->ent);
+}
+
+struct all_attrs_item {
+	const struct git_attr *attr;
+	const char *value;
+	/*
+	 * If 'macro' is non-NULL, indicates that 'attr' is a macro based on
+	 * the current attribute stack and contains a pointer to the match_attr
+	 * definition of the macro
+	 */
+	const struct match_attr *macro;
+};
+
+/*
+ * Reallocate and reinitialize the array of all attributes (which is used in
+ * the attribute collection process) in 'check' based on the global dictionary
+ * of attributes.
+ */
+static void all_attrs_init(struct attr_hashmap *map, struct attr_check *check)
+{
+	int i;
+	unsigned int size;
+
+	hashmap_lock(map);
+
+	size = hashmap_get_size(&map->map);
+	if (size < check->all_attrs_nr)
+		BUG("interned attributes shouldn't be deleted");
+
+	/*
+	 * If the number of attributes in the global dictionary has increased
+	 * (or this attr_check instance doesn't have an initialized all_attrs
+	 * field), reallocate the provided attr_check instance's all_attrs
+	 * field and fill each entry with its corresponding git_attr.
+	 */
+	if (size != check->all_attrs_nr) {
+		struct attr_hash_entry *e;
+		struct hashmap_iter iter;
+
+		REALLOC_ARRAY(check->all_attrs, size);
+		check->all_attrs_nr = size;
+
+		hashmap_for_each_entry(&map->map, &iter, e,
+					ent /* member name */) {
+			const struct git_attr *a = e->value;
+			check->all_attrs[a->attr_nr].attr = a;
+		}
+	}
+
+	hashmap_unlock(map);
+
+	/*
+	 * Re-initialize every entry in check->all_attrs.
+	 * This re-initialization can live outside of the locked region since
+	 * the attribute dictionary is no longer being accessed.
+	 */
+	for (i = 0; i < check->all_attrs_nr; i++) {
+		check->all_attrs[i].value = ATTR__UNKNOWN;
+		check->all_attrs[i].macro = NULL;
+	}
+}
+
+static int attr_name_valid(const char *name, size_t namelen)
+{
+	/*
+	 * Attribute name cannot begin with '-' and must consist of
+	 * characters from [-A-Za-z0-9_.].
+	 */
+	if (namelen <= 0 || *name == '-')
+		return 0;
+	while (namelen--) {
+		char ch = *name++;
+		if (! (ch == '-' || ch == '.' || ch == '_' ||
+		       ('0' <= ch && ch <= '9') ||
+		       ('a' <= ch && ch <= 'z') ||
+		       ('A' <= ch && ch <= 'Z')) )
+			return 0;
+	}
+	return 1;
+}
+
+static void report_invalid_attr(const char *name, size_t len,
+				const char *src, int lineno)
+{
+	struct strbuf err = STRBUF_INIT;
+	strbuf_addf(&err, _("%.*s is not a valid attribute name"),
+		    (int) len, name);
+	fprintf(stderr, "%s: %s:%d\n", err.buf, src, lineno);
+	strbuf_release(&err);
+}
+
+/*
+ * Given a 'name', lookup and return the corresponding attribute in the global
+ * dictionary.  If no entry is found, create a new attribute and store it in
+ * the dictionary.
+ */
+static const struct git_attr *git_attr_internal(const char *name, size_t namelen)
+{
+	struct git_attr *a;
+
+	if (!attr_name_valid(name, namelen))
+		return NULL;
+
+	hashmap_lock(&g_attr_hashmap);
+
+	a = attr_hashmap_get(&g_attr_hashmap, name, namelen);
+
+	if (!a) {
+		FLEX_ALLOC_MEM(a, name, name, namelen);
+		a->attr_nr = hashmap_get_size(&g_attr_hashmap.map);
+
+		attr_hashmap_add(&g_attr_hashmap, a->name, namelen, a);
+		if (a->attr_nr != hashmap_get_size(&g_attr_hashmap.map) - 1)
+			die(_("unable to add additional attribute"));
+	}
+
+	hashmap_unlock(&g_attr_hashmap);
+
+	return a;
+}
+
+const struct git_attr *git_attr(const char *name)
+{
+	return git_attr_internal(name, strlen(name));
+}
+
+/* What does a matched pattern decide? */
+struct attr_state {
+	const struct git_attr *attr;
+	const char *setto;
+};
+
+struct pattern {
+	const char *pattern;
+	int patternlen;
+	int nowildcardlen;
+	unsigned flags;		/* PATTERN_FLAG_* */
+};
+
+/*
+ * One rule, as from a .gitattributes file.
+ *
+ * If is_macro is true, then u.attr is a pointer to the git_attr being
+ * defined.
+ *
+ * If is_macro is false, then u.pat is the filename pattern to which the
+ * rule applies.
+ *
+ * In either case, num_attr is the number of attributes affected by
+ * this rule, and state is an array listing them.  The attributes are
+ * listed as they appear in the file (macros unexpanded).
+ */
+struct match_attr {
+	union {
+		struct pattern pat;
+		const struct git_attr *attr;
+	} u;
+	char is_macro;
+	size_t num_attr;
+	struct attr_state state[FLEX_ARRAY];
+};
+
+static const char blank[] = " \t\r\n";
+
+/* Flags usable in read_attr() and parse_attr_line() family of functions. */
+#define READ_ATTR_MACRO_OK (1<<0)
+#define READ_ATTR_NOFOLLOW (1<<1)
+
+/*
+ * Parse a whitespace-delimited attribute state (i.e., "attr",
+ * "-attr", "!attr", or "attr=value") from the string starting at src.
+ * If e is not NULL, write the results to *e.  Return a pointer to the
+ * remainder of the string (with leading whitespace removed), or NULL
+ * if there was an error.
+ */
+static const char *parse_attr(const char *src, int lineno, const char *cp,
+			      struct attr_state *e)
+{
+	const char *ep, *equals;
+	size_t len;
+
+	ep = cp + strcspn(cp, blank);
+	equals = strchr(cp, '=');
+	if (equals && ep < equals)
+		equals = NULL;
+	if (equals)
+		len = equals - cp;
+	else
+		len = ep - cp;
+	if (!e) {
+		if (*cp == '-' || *cp == '!') {
+			cp++;
+			len--;
+		}
+		if (!attr_name_valid(cp, len)) {
+			report_invalid_attr(cp, len, src, lineno);
+			return NULL;
+		}
+	} else {
+		/*
+		 * As this function is always called twice, once with
+		 * e == NULL in the first pass and then e != NULL in
+		 * the second pass, no need for attr_name_valid()
+		 * check here.
+		 */
+		if (*cp == '-' || *cp == '!') {
+			e->setto = (*cp == '-') ? ATTR__FALSE : ATTR__UNSET;
+			cp++;
+			len--;
+		}
+		else if (!equals)
+			e->setto = ATTR__TRUE;
+		else {
+			e->setto = xmemdupz(equals + 1, ep - equals - 1);
+		}
+		e->attr = git_attr_internal(cp, len);
+	}
+	return ep + strspn(ep, blank);
+}
+
+static struct match_attr *parse_attr_line(const char *line, const char *src,
+					  int lineno, unsigned flags)
+{
+	size_t namelen, num_attr, i;
+	const char *cp, *name, *states;
+	struct match_attr *res = NULL;
+	int is_macro;
+	struct strbuf pattern = STRBUF_INIT;
+
+	cp = line + strspn(line, blank);
+	if (!*cp || *cp == '#')
+		return NULL;
+	name = cp;
+
+	if (strlen(line) >= ATTR_MAX_LINE_LENGTH) {
+		warning(_("ignoring overly long attributes line %d"), lineno);
+		return NULL;
+	}
+
+	if (*cp == '"' && !unquote_c_style(&pattern, name, &states)) {
+		name = pattern.buf;
+		namelen = pattern.len;
+	} else {
+		namelen = strcspn(name, blank);
+		states = name + namelen;
+	}
+
+	if (strlen(ATTRIBUTE_MACRO_PREFIX) < namelen &&
+	    starts_with(name, ATTRIBUTE_MACRO_PREFIX)) {
+		if (!(flags & READ_ATTR_MACRO_OK)) {
+			fprintf_ln(stderr, _("%s not allowed: %s:%d"),
+				   name, src, lineno);
+			goto fail_return;
+		}
+		is_macro = 1;
+		name += strlen(ATTRIBUTE_MACRO_PREFIX);
+		name += strspn(name, blank);
+		namelen = strcspn(name, blank);
+		if (!attr_name_valid(name, namelen)) {
+			report_invalid_attr(name, namelen, src, lineno);
+			goto fail_return;
+		}
+	}
+	else
+		is_macro = 0;
+
+	states += strspn(states, blank);
+
+	/* First pass to count the attr_states */
+	for (cp = states, num_attr = 0; *cp; num_attr++) {
+		cp = parse_attr(src, lineno, cp, NULL);
+		if (!cp)
+			goto fail_return;
+	}
+
+	res = xcalloc(1, st_add3(sizeof(*res),
+				 st_mult(sizeof(struct attr_state), num_attr),
+				 is_macro ? 0 : namelen + 1));
+	if (is_macro) {
+		res->u.attr = git_attr_internal(name, namelen);
+	} else {
+		char *p = (char *)&(res->state[num_attr]);
+		memcpy(p, name, namelen);
+		res->u.pat.pattern = p;
+		parse_path_pattern(&res->u.pat.pattern,
+				      &res->u.pat.patternlen,
+				      &res->u.pat.flags,
+				      &res->u.pat.nowildcardlen);
+		if (res->u.pat.flags & PATTERN_FLAG_NEGATIVE) {
+			warning(_("Negative patterns are ignored in git attributes\n"
+				  "Use '\\!' for literal leading exclamation."));
+			goto fail_return;
+		}
+	}
+	res->is_macro = is_macro;
+	res->num_attr = num_attr;
+
+	/* Second pass to fill the attr_states */
+	for (cp = states, i = 0; *cp; i++) {
+		cp = parse_attr(src, lineno, cp, &(res->state[i]));
+	}
+
+	strbuf_release(&pattern);
+	return res;
+
+fail_return:
+	strbuf_release(&pattern);
+	free(res);
+	return NULL;
+}
+
+/*
+ * Like info/exclude and .gitignore, the attribute information can
+ * come from many places.
+ *
+ * (1) .gitattributes file of the same directory;
+ * (2) .gitattributes file of the parent directory if (1) does not have
+ *      any match; this goes recursively upwards, just like .gitignore.
+ * (3) $GIT_DIR/info/attributes, which overrides both of the above.
+ *
+ * In the same file, later entries override the earlier match, so in the
+ * global list, we would have entries from info/attributes the earliest
+ * (reading the file from top to bottom), .gitattributes of the root
+ * directory (again, reading the file from top to bottom) down to the
+ * current directory, and then scan the list backwards to find the first match.
+ * This is exactly the same as what is_excluded() does in dir.c to deal with
+ * .gitignore file and info/excludes file as a fallback.
+ */
+
+struct attr_stack {
+	struct attr_stack *prev;
+	char *origin;
+	size_t originlen;
+	unsigned num_matches;
+	unsigned alloc;
+	struct match_attr **attrs;
+};
+
+static void attr_stack_free(struct attr_stack *e)
+{
+	unsigned i;
+	free(e->origin);
+	for (i = 0; i < e->num_matches; i++) {
+		struct match_attr *a = e->attrs[i];
+		size_t j;
+
+		for (j = 0; j < a->num_attr; j++) {
+			const char *setto = a->state[j].setto;
+			if (setto == ATTR__TRUE ||
+			    setto == ATTR__FALSE ||
+			    setto == ATTR__UNSET ||
+			    setto == ATTR__UNKNOWN)
+				;
+			else
+				free((char *) setto);
+		}
+		free(a);
+	}
+	free(e->attrs);
+	free(e);
+}
+
+static void drop_attr_stack(struct attr_stack **stack)
+{
+	while (*stack) {
+		struct attr_stack *elem = *stack;
+		*stack = elem->prev;
+		attr_stack_free(elem);
+	}
+}
+
+/* List of all attr_check structs; access should be surrounded by mutex */
+static struct check_vector {
+	size_t nr;
+	size_t alloc;
+	struct attr_check **checks;
+	pthread_mutex_t mutex;
+} check_vector;
+
+static inline void vector_lock(void)
+{
+	pthread_mutex_lock(&check_vector.mutex);
+}
+
+static inline void vector_unlock(void)
+{
+	pthread_mutex_unlock(&check_vector.mutex);
+}
+
+static void check_vector_add(struct attr_check *c)
+{
+	vector_lock();
+
+	ALLOC_GROW(check_vector.checks,
+		   check_vector.nr + 1,
+		   check_vector.alloc);
+	check_vector.checks[check_vector.nr++] = c;
+
+	vector_unlock();
+}
+
+static void check_vector_remove(struct attr_check *check)
+{
+	int i;
+
+	vector_lock();
+
+	/* Find entry */
+	for (i = 0; i < check_vector.nr; i++)
+		if (check_vector.checks[i] == check)
+			break;
+
+	if (i >= check_vector.nr)
+		BUG("no entry found");
+
+	/* shift entries over */
+	for (; i < check_vector.nr - 1; i++)
+		check_vector.checks[i] = check_vector.checks[i + 1];
+
+	check_vector.nr--;
+
+	vector_unlock();
+}
+
+/* Iterate through all attr_check instances and drop their stacks */
+static void drop_all_attr_stacks(void)
+{
+	int i;
+
+	vector_lock();
+
+	for (i = 0; i < check_vector.nr; i++) {
+		drop_attr_stack(&check_vector.checks[i]->stack);
+	}
+
+	vector_unlock();
+}
+
+struct attr_check *attr_check_alloc(void)
+{
+	struct attr_check *c = xcalloc(1, sizeof(struct attr_check));
+
+	/* save pointer to the check struct */
+	check_vector_add(c);
+
+	return c;
+}
+
+struct attr_check *attr_check_initl(const char *one, ...)
+{
+	struct attr_check *check;
+	int cnt;
+	va_list params;
+	const char *param;
+
+	va_start(params, one);
+	for (cnt = 1; (param = va_arg(params, const char *)) != NULL; cnt++)
+		;
+	va_end(params);
+
+	check = attr_check_alloc();
+	check->nr = cnt;
+	check->alloc = cnt;
+	CALLOC_ARRAY(check->items, cnt);
+
+	check->items[0].attr = git_attr(one);
+	va_start(params, one);
+	for (cnt = 1; cnt < check->nr; cnt++) {
+		const struct git_attr *attr;
+		param = va_arg(params, const char *);
+		if (!param)
+			BUG("counted %d != ended at %d",
+			    check->nr, cnt);
+		attr = git_attr(param);
+		if (!attr)
+			BUG("%s: not a valid attribute name", param);
+		check->items[cnt].attr = attr;
+	}
+	va_end(params);
+	return check;
+}
+
+struct attr_check *attr_check_dup(const struct attr_check *check)
+{
+	struct attr_check *ret;
+
+	if (!check)
+		return NULL;
+
+	ret = attr_check_alloc();
+
+	ret->nr = check->nr;
+	ret->alloc = check->alloc;
+	DUP_ARRAY(ret->items, check->items, ret->nr);
+
+	return ret;
+}
+
+struct attr_check_item *attr_check_append(struct attr_check *check,
+					  const struct git_attr *attr)
+{
+	struct attr_check_item *item;
+
+	ALLOC_GROW(check->items, check->nr + 1, check->alloc);
+	item = &check->items[check->nr++];
+	item->attr = attr;
+	return item;
+}
+
+void attr_check_reset(struct attr_check *check)
+{
+	check->nr = 0;
+}
+
+void attr_check_clear(struct attr_check *check)
+{
+	FREE_AND_NULL(check->items);
+	check->alloc = 0;
+	check->nr = 0;
+
+	FREE_AND_NULL(check->all_attrs);
+	check->all_attrs_nr = 0;
+
+	drop_attr_stack(&check->stack);
+}
+
+void attr_check_free(struct attr_check *check)
+{
+	if (check) {
+		/* Remove check from the check vector */
+		check_vector_remove(check);
+
+		attr_check_clear(check);
+		free(check);
+	}
+}
+
+static const char *builtin_attr[] = {
+	"[attr]binary -diff -merge -text",
+	NULL,
+};
+
+static void handle_attr_line(struct attr_stack *res,
+			     const char *line,
+			     const char *src,
+			     int lineno,
+			     unsigned flags)
+{
+	struct match_attr *a;
+
+	a = parse_attr_line(line, src, lineno, flags);
+	if (!a)
+		return;
+	ALLOC_GROW_BY(res->attrs, res->num_matches, 1, res->alloc);
+	res->attrs[res->num_matches - 1] = a;
+}
+
+static struct attr_stack *read_attr_from_array(const char **list)
+{
+	struct attr_stack *res;
+	const char *line;
+	int lineno = 0;
+
+	CALLOC_ARRAY(res, 1);
+	while ((line = *(list++)) != NULL)
+		handle_attr_line(res, line, "[builtin]", ++lineno,
+				 READ_ATTR_MACRO_OK);
+	return res;
+}
+
+/*
+ * Callers into the attribute system assume there is a single, system-wide
+ * global state where attributes are read from and when the state is flipped by
+ * calling git_attr_set_direction(), the stack frames that have been
+ * constructed need to be discarded so that subsequent calls into the
+ * attribute system will lazily read from the right place.  Since changing
+ * direction causes a global paradigm shift, it should not ever be called while
+ * another thread could potentially be calling into the attribute system.
+ */
+static enum git_attr_direction direction;
+
+void git_attr_set_direction(enum git_attr_direction new_direction)
+{
+	if (is_bare_repository() && new_direction != GIT_ATTR_INDEX)
+		BUG("non-INDEX attr direction in a bare repo");
+
+	if (new_direction != direction)
+		drop_all_attr_stacks();
+
+	direction = new_direction;
+}
+
+static struct attr_stack *read_attr_from_file(const char *path, unsigned flags)
+{
+	struct strbuf buf = STRBUF_INIT;
+	int fd;
+	FILE *fp;
+	struct attr_stack *res;
+	int lineno = 0;
+	struct stat st;
+
+	if (flags & READ_ATTR_NOFOLLOW)
+		fd = open_nofollow(path, O_RDONLY);
+	else
+		fd = open(path, O_RDONLY);
+
+	if (fd < 0) {
+		warn_on_fopen_errors(path);
+		return NULL;
+	}
+	fp = xfdopen(fd, "r");
+	if (fstat(fd, &st)) {
+		warning_errno(_("cannot fstat gitattributes file '%s'"), path);
+		fclose(fp);
+		return NULL;
+	}
+	if (st.st_size >= ATTR_MAX_FILE_SIZE) {
+		warning(_("ignoring overly large gitattributes file '%s'"), path);
+		fclose(fp);
+		return NULL;
+	}
+
+	CALLOC_ARRAY(res, 1);
+	while (strbuf_getline(&buf, fp) != EOF) {
+		if (!lineno && starts_with(buf.buf, utf8_bom))
+			strbuf_remove(&buf, 0, strlen(utf8_bom));
+		handle_attr_line(res, buf.buf, path, ++lineno, flags);
+	}
+
+	fclose(fp);
+	strbuf_release(&buf);
+	return res;
+}
+
+static struct attr_stack *read_attr_from_buf(char *buf, const char *path,
+					     unsigned flags)
+{
+	struct attr_stack *res;
+	char *sp;
+	int lineno = 0;
+
+	if (!buf)
+		return NULL;
+
+	CALLOC_ARRAY(res, 1);
+	for (sp = buf; *sp;) {
+		char *ep;
+		int more;
+
+		ep = strchrnul(sp, '\n');
+		more = (*ep == '\n');
+		*ep = '\0';
+		handle_attr_line(res, sp, path, ++lineno, flags);
+		sp = ep + more;
+	}
+	free(buf);
+
+	return res;
+}
+
+static struct attr_stack *read_attr_from_blob(struct index_state *istate,
+					      const struct object_id *tree_oid,
+					      const char *path, unsigned flags)
+{
+	struct object_id oid;
+	unsigned long sz;
+	enum object_type type;
+	void *buf;
+	unsigned short mode;
+
+	if (!tree_oid)
+		return NULL;
+
+	if (get_tree_entry(istate->repo, tree_oid, path, &oid, &mode))
+		return NULL;
+
+	buf = repo_read_object_file(istate->repo, &oid, &type, &sz);
+	if (!buf || type != OBJ_BLOB) {
+		free(buf);
+		return NULL;
+	}
+
+	return read_attr_from_buf(buf, path, flags);
+}
+
+static struct attr_stack *read_attr_from_index(struct index_state *istate,
+					       const char *path, unsigned flags)
+{
+	struct attr_stack *stack = NULL;
+	char *buf;
+	unsigned long size;
+	int sparse_dir_pos = -1;
+
+	if (!istate)
+		return NULL;
+
+	/*
+	 * When handling sparse-checkouts, .gitattributes files
+	 * may reside within a sparse directory. We distinguish
+	 * whether a path exists directly in the index or not by
+	 * evaluating if 'pos' is negative.
+	 * If 'pos' is negative, the path is not directly present
+	 * in the index and is likely within a sparse directory.
+	 * For paths not in the index, The absolute value of 'pos'
+	 * minus 1 gives us the position where the path would be
+	 * inserted in lexicographic order within the index.
+	 * We then subtract another 1 from this value
+	 * (sparse_dir_pos = -pos - 2) to find the position of the
+	 * last index entry which is lexicographically smaller than
+	 * the path. This would be the sparse directory containing
+	 * the path. By identifying the sparse directory containing
+	 * the path, we can correctly read the attributes specified
+	 * in the .gitattributes file from the tree object of the
+	 * sparse directory.
+	 */
+	if (!path_in_cone_mode_sparse_checkout(path, istate)) {
+		int pos = index_name_pos_sparse(istate, path, strlen(path));
+
+		if (pos < 0)
+			sparse_dir_pos = -pos - 2;
+	}
+
+	if (sparse_dir_pos >= 0 &&
+	    S_ISSPARSEDIR(istate->cache[sparse_dir_pos]->ce_mode) &&
+	    !strncmp(istate->cache[sparse_dir_pos]->name, path, ce_namelen(istate->cache[sparse_dir_pos]))) {
+		const char *relative_path = path + ce_namelen(istate->cache[sparse_dir_pos]);
+		stack = read_attr_from_blob(istate, &istate->cache[sparse_dir_pos]->oid, relative_path, flags);
+	} else {
+		buf = read_blob_data_from_index(istate, path, &size);
+		if (!buf)
+			return NULL;
+		if (size >= ATTR_MAX_FILE_SIZE) {
+			warning(_("ignoring overly large gitattributes blob '%s'"), path);
+			return NULL;
+		}
+		stack = read_attr_from_buf(buf, path, flags);
+	}
+	return stack;
+}
+
+static struct attr_stack *read_attr(struct index_state *istate,
+				    const struct object_id *tree_oid,
+				    const char *path, unsigned flags)
+{
+	struct attr_stack *res = NULL;
+
+	if (direction == GIT_ATTR_INDEX) {
+		res = read_attr_from_index(istate, path, flags);
+	} else if (tree_oid) {
+		res = read_attr_from_blob(istate, tree_oid, path, flags);
+	} else if (!is_bare_repository()) {
+		if (direction == GIT_ATTR_CHECKOUT) {
+			res = read_attr_from_index(istate, path, flags);
+			if (!res)
+				res = read_attr_from_file(path, flags);
+		} else if (direction == GIT_ATTR_CHECKIN) {
+			res = read_attr_from_file(path, flags);
+			if (!res)
+				/*
+				 * There is no checked out .gitattributes file
+				 * there, but we might have it in the index.
+				 * We allow operation in a sparsely checked out
+				 * work tree, so read from it.
+				 */
+				res = read_attr_from_index(istate, path, flags);
+		}
+	}
+
+	if (!res)
+		CALLOC_ARRAY(res, 1);
+	return res;
+}
+
+const char *git_attr_system_file(void)
+{
+	static const char *system_wide;
+	if (!system_wide)
+		system_wide = system_path(ETC_GITATTRIBUTES);
+	return system_wide;
+}
+
+const char *git_attr_global_file(void)
+{
+	if (!git_attributes_file)
+		git_attributes_file = xdg_config_home("attributes");
+
+	return git_attributes_file;
+}
+
+int git_attr_system_is_enabled(void)
+{
+	return !git_env_bool("GIT_ATTR_NOSYSTEM", 0);
+}
+
+static GIT_PATH_FUNC(git_path_info_attributes, INFOATTRIBUTES_FILE)
+
+static void push_stack(struct attr_stack **attr_stack_p,
+		       struct attr_stack *elem, char *origin, size_t originlen)
+{
+	if (elem) {
+		elem->origin = origin;
+		if (origin)
+			elem->originlen = originlen;
+		elem->prev = *attr_stack_p;
+		*attr_stack_p = elem;
+	}
+}
+
+static void bootstrap_attr_stack(struct index_state *istate,
+				 const struct object_id *tree_oid,
+				 struct attr_stack **stack)
+{
+	struct attr_stack *e;
+	unsigned flags = READ_ATTR_MACRO_OK;
+
+	if (*stack)
+		return;
+
+	/* builtin frame */
+	e = read_attr_from_array(builtin_attr);
+	push_stack(stack, e, NULL, 0);
+
+	/* system-wide frame */
+	if (git_attr_system_is_enabled()) {
+		e = read_attr_from_file(git_attr_system_file(), flags);
+		push_stack(stack, e, NULL, 0);
+	}
+
+	/* home directory */
+	if (git_attr_global_file()) {
+		e = read_attr_from_file(git_attr_global_file(), flags);
+		push_stack(stack, e, NULL, 0);
+	}
+
+	/* root directory */
+	e = read_attr(istate, tree_oid, GITATTRIBUTES_FILE, flags | READ_ATTR_NOFOLLOW);
+	push_stack(stack, e, xstrdup(""), 0);
+
+	/* info frame */
+	if (startup_info->have_repository)
+		e = read_attr_from_file(git_path_info_attributes(), flags);
+	else
+		e = NULL;
+	if (!e)
+		CALLOC_ARRAY(e, 1);
+	push_stack(stack, e, NULL, 0);
+}
+
+static void prepare_attr_stack(struct index_state *istate,
+			       const struct object_id *tree_oid,
+			       const char *path, int dirlen,
+			       struct attr_stack **stack)
+{
+	struct attr_stack *info;
+	struct strbuf pathbuf = STRBUF_INIT;
+
+	/*
+	 * At the bottom of the attribute stack is the built-in
+	 * set of attribute definitions, followed by the contents
+	 * of $(prefix)/etc/gitattributes and a file specified by
+	 * core.attributesfile.  Then, contents from
+	 * .gitattributes files from directories closer to the
+	 * root to the ones in deeper directories are pushed
+	 * to the stack.  Finally, at the very top of the stack
+	 * we always keep the contents of $GIT_DIR/info/attributes.
+	 *
+	 * When checking, we use entries from near the top of the
+	 * stack, preferring $GIT_DIR/info/attributes, then
+	 * .gitattributes in deeper directories to shallower ones,
+	 * and finally use the built-in set as the default.
+	 */
+	bootstrap_attr_stack(istate, tree_oid, stack);
+
+	/*
+	 * Pop the "info" one that is always at the top of the stack.
+	 */
+	info = *stack;
+	*stack = info->prev;
+
+	/*
+	 * Pop the ones from directories that are not the prefix of
+	 * the path we are checking. Break out of the loop when we see
+	 * the root one (whose origin is an empty string "") or the builtin
+	 * one (whose origin is NULL) without popping it.
+	 */
+	while ((*stack)->origin) {
+		int namelen = (*stack)->originlen;
+		struct attr_stack *elem;
+
+		elem = *stack;
+		if (namelen <= dirlen &&
+		    !strncmp(elem->origin, path, namelen) &&
+		    (!namelen || path[namelen] == '/'))
+			break;
+
+		*stack = elem->prev;
+		attr_stack_free(elem);
+	}
+
+	/*
+	 * bootstrap_attr_stack() should have added, and the
+	 * above loop should have stopped before popping, the
+	 * root element whose attr_stack->origin is set to an
+	 * empty string.
+	 */
+	assert((*stack)->origin);
+
+	strbuf_addstr(&pathbuf, (*stack)->origin);
+	/* Build up to the directory 'path' is in */
+	while (pathbuf.len < dirlen) {
+		size_t len = pathbuf.len;
+		struct attr_stack *next;
+		char *origin;
+
+		/* Skip path-separator */
+		if (len < dirlen && is_dir_sep(path[len]))
+			len++;
+		/* Find the end of the next component */
+		while (len < dirlen && !is_dir_sep(path[len]))
+			len++;
+
+		if (pathbuf.len > 0)
+			strbuf_addch(&pathbuf, '/');
+		strbuf_add(&pathbuf, path + pathbuf.len, (len - pathbuf.len));
+		strbuf_addf(&pathbuf, "/%s", GITATTRIBUTES_FILE);
+
+		next = read_attr(istate, tree_oid, pathbuf.buf, READ_ATTR_NOFOLLOW);
+
+		/* reset the pathbuf to not include "/.gitattributes" */
+		strbuf_setlen(&pathbuf, len);
+
+		origin = xstrdup(pathbuf.buf);
+		push_stack(stack, next, origin, len);
+	}
+
+	/*
+	 * Finally push the "info" one at the top of the stack.
+	 */
+	push_stack(stack, info, NULL, 0);
+
+	strbuf_release(&pathbuf);
+}
+
+static int path_matches(const char *pathname, int pathlen,
+			int basename_offset,
+			const struct pattern *pat,
+			const char *base, int baselen)
+{
+	const char *pattern = pat->pattern;
+	int prefix = pat->nowildcardlen;
+	int isdir = (pathlen && pathname[pathlen - 1] == '/');
+
+	if ((pat->flags & PATTERN_FLAG_MUSTBEDIR) && !isdir)
+		return 0;
+
+	if (pat->flags & PATTERN_FLAG_NODIR) {
+		return match_basename(pathname + basename_offset,
+				      pathlen - basename_offset - isdir,
+				      pattern, prefix,
+				      pat->patternlen, pat->flags);
+	}
+	return match_pathname(pathname, pathlen - isdir,
+			      base, baselen,
+			      pattern, prefix, pat->patternlen);
+}
+
+static int macroexpand_one(struct all_attrs_item *all_attrs, int nr, int rem);
+
+static int fill_one(struct all_attrs_item *all_attrs,
+		    const struct match_attr *a, int rem)
+{
+	size_t i;
+
+	for (i = a->num_attr; rem > 0 && i > 0; i--) {
+		const struct git_attr *attr = a->state[i - 1].attr;
+		const char **n = &(all_attrs[attr->attr_nr].value);
+		const char *v = a->state[i - 1].setto;
+
+		if (*n == ATTR__UNKNOWN) {
+			*n = v;
+			rem--;
+			rem = macroexpand_one(all_attrs, attr->attr_nr, rem);
+		}
+	}
+	return rem;
+}
+
+static int fill(const char *path, int pathlen, int basename_offset,
+		const struct attr_stack *stack,
+		struct all_attrs_item *all_attrs, int rem)
+{
+	for (; rem > 0 && stack; stack = stack->prev) {
+		unsigned i;
+		const char *base = stack->origin ? stack->origin : "";
+
+		for (i = stack->num_matches; 0 < rem && 0 < i; i--) {
+			const struct match_attr *a = stack->attrs[i - 1];
+			if (a->is_macro)
+				continue;
+			if (path_matches(path, pathlen, basename_offset,
+					 &a->u.pat, base, stack->originlen))
+				rem = fill_one(all_attrs, a, rem);
+		}
+	}
+
+	return rem;
+}
+
+static int macroexpand_one(struct all_attrs_item *all_attrs, int nr, int rem)
+{
+	const struct all_attrs_item *item = &all_attrs[nr];
+
+	if (item->macro && item->value == ATTR__TRUE)
+		return fill_one(all_attrs, item->macro, rem);
+	else
+		return rem;
+}
+
+/*
+ * Marks the attributes which are macros based on the attribute stack.
+ * This prevents having to search through the attribute stack each time
+ * a macro needs to be expanded during the fill stage.
+ */
+static void determine_macros(struct all_attrs_item *all_attrs,
+			     const struct attr_stack *stack)
+{
+	for (; stack; stack = stack->prev) {
+		unsigned i;
+		for (i = stack->num_matches; i > 0; i--) {
+			const struct match_attr *ma = stack->attrs[i - 1];
+			if (ma->is_macro) {
+				unsigned int n = ma->u.attr->attr_nr;
+				if (!all_attrs[n].macro) {
+					all_attrs[n].macro = ma;
+				}
+			}
+		}
+	}
+}
+
+/*
+ * Collect attributes for path into the array pointed to by check->all_attrs.
+ * If check->check_nr is non-zero, only attributes in check[] are collected.
+ * Otherwise all attributes are collected.
+ */
+static void collect_some_attrs(struct index_state *istate,
+			       const struct object_id *tree_oid,
+			       const char *path, struct attr_check *check)
+{
+	int pathlen, rem, dirlen;
+	const char *cp, *last_slash = NULL;
+	int basename_offset;
+
+	for (cp = path; *cp; cp++) {
+		if (*cp == '/' && cp[1])
+			last_slash = cp;
+	}
+	pathlen = cp - path;
+	if (last_slash) {
+		basename_offset = last_slash + 1 - path;
+		dirlen = last_slash - path;
+	} else {
+		basename_offset = 0;
+		dirlen = 0;
+	}
+
+	prepare_attr_stack(istate, tree_oid, path, dirlen, &check->stack);
+	all_attrs_init(&g_attr_hashmap, check);
+	determine_macros(check->all_attrs, check->stack);
+
+	rem = check->all_attrs_nr;
+	fill(path, pathlen, basename_offset, check->stack, check->all_attrs, rem);
+}
+
+static const char *default_attr_source_tree_object_name;
+static int ignore_bad_attr_tree;
+
+void set_git_attr_source(const char *tree_object_name)
+{
+	default_attr_source_tree_object_name = xstrdup(tree_object_name);
+}
+
+static void compute_default_attr_source(struct object_id *attr_source)
+{
+	if (!default_attr_source_tree_object_name)
+		default_attr_source_tree_object_name = getenv(GIT_ATTR_SOURCE_ENVIRONMENT);
+
+	if (!default_attr_source_tree_object_name && git_attr_tree) {
+		default_attr_source_tree_object_name = git_attr_tree;
+		ignore_bad_attr_tree = 1;
+	}
+
+	if (!default_attr_source_tree_object_name &&
+	    startup_info->have_repository &&
+	    is_bare_repository()) {
+		default_attr_source_tree_object_name = "HEAD";
+		ignore_bad_attr_tree = 1;
+	}
+
+	if (!default_attr_source_tree_object_name || !is_null_oid(attr_source))
+		return;
+
+	if (repo_get_oid_treeish(the_repository,
+				 default_attr_source_tree_object_name,
+				 attr_source) && !ignore_bad_attr_tree)
+		die(_("bad --attr-source or GIT_ATTR_SOURCE"));
+}
+
+static struct object_id *default_attr_source(void)
+{
+	static struct object_id attr_source;
+
+	if (is_null_oid(&attr_source))
+		compute_default_attr_source(&attr_source);
+	if (is_null_oid(&attr_source))
+		return NULL;
+	return &attr_source;
+}
+
+void git_check_attr(struct index_state *istate,
+		    const char *path,
+		    struct attr_check *check)
+{
+	int i;
+	const struct object_id *tree_oid = default_attr_source();
+
+	collect_some_attrs(istate, tree_oid, path, check);
+
+	for (i = 0; i < check->nr; i++) {
+		unsigned int n = check->items[i].attr->attr_nr;
+		const char *value = check->all_attrs[n].value;
+		if (value == ATTR__UNKNOWN)
+			value = ATTR__UNSET;
+		check->items[i].value = value;
+	}
+}
+
+void git_all_attrs(struct index_state *istate,
+		   const char *path, struct attr_check *check)
+{
+	int i;
+	const struct object_id *tree_oid = default_attr_source();
+
+	attr_check_reset(check);
+	collect_some_attrs(istate, tree_oid, path, check);
+
+	for (i = 0; i < check->all_attrs_nr; i++) {
+		const char *name = check->all_attrs[i].attr->name;
+		const char *value = check->all_attrs[i].value;
+		struct attr_check_item *item;
+		if (value == ATTR__UNSET || value == ATTR__UNKNOWN)
+			continue;
+		item = attr_check_append(check, git_attr(name));
+		item->value = value;
+	}
+}
+
+void attr_start(void)
+{
+	pthread_mutex_init(&g_attr_hashmap.mutex, NULL);
+	pthread_mutex_init(&check_vector.mutex, NULL);
+}