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-rw-r--r--third_party/git/sha1-name.c1944
1 files changed, 1944 insertions, 0 deletions
diff --git a/third_party/git/sha1-name.c b/third_party/git/sha1-name.c
new file mode 100644
index 000000000000..2989e27b717a
--- /dev/null
+++ b/third_party/git/sha1-name.c
@@ -0,0 +1,1944 @@
+#include "cache.h"
+#include "config.h"
+#include "tag.h"
+#include "commit.h"
+#include "tree.h"
+#include "blob.h"
+#include "tree-walk.h"
+#include "refs.h"
+#include "remote.h"
+#include "dir.h"
+#include "sha1-array.h"
+#include "packfile.h"
+#include "object-store.h"
+#include "repository.h"
+#include "submodule.h"
+#include "midx.h"
+#include "commit-reach.h"
+
+static int get_oid_oneline(struct repository *r, const char *, struct object_id *, struct commit_list *);
+
+typedef int (*disambiguate_hint_fn)(struct repository *, const struct object_id *, void *);
+
+struct disambiguate_state {
+	int len; /* length of prefix in hex chars */
+	char hex_pfx[GIT_MAX_HEXSZ + 1];
+	struct object_id bin_pfx;
+
+	struct repository *repo;
+	disambiguate_hint_fn fn;
+	void *cb_data;
+	struct object_id candidate;
+	unsigned candidate_exists:1;
+	unsigned candidate_checked:1;
+	unsigned candidate_ok:1;
+	unsigned disambiguate_fn_used:1;
+	unsigned ambiguous:1;
+	unsigned always_call_fn:1;
+};
+
+static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
+{
+	if (ds->always_call_fn) {
+		ds->ambiguous = ds->fn(ds->repo, current, ds->cb_data) ? 1 : 0;
+		return;
+	}
+	if (!ds->candidate_exists) {
+		/* this is the first candidate */
+		oidcpy(&ds->candidate, current);
+		ds->candidate_exists = 1;
+		return;
+	} else if (oideq(&ds->candidate, current)) {
+		/* the same as what we already have seen */
+		return;
+	}
+
+	if (!ds->fn) {
+		/* cannot disambiguate between ds->candidate and current */
+		ds->ambiguous = 1;
+		return;
+	}
+
+	if (!ds->candidate_checked) {
+		ds->candidate_ok = ds->fn(ds->repo, &ds->candidate, ds->cb_data);
+		ds->disambiguate_fn_used = 1;
+		ds->candidate_checked = 1;
+	}
+
+	if (!ds->candidate_ok) {
+		/* discard the candidate; we know it does not satisfy fn */
+		oidcpy(&ds->candidate, current);
+		ds->candidate_checked = 0;
+		return;
+	}
+
+	/* if we reach this point, we know ds->candidate satisfies fn */
+	if (ds->fn(ds->repo, current, ds->cb_data)) {
+		/*
+		 * if both current and candidate satisfy fn, we cannot
+		 * disambiguate.
+		 */
+		ds->candidate_ok = 0;
+		ds->ambiguous = 1;
+	}
+
+	/* otherwise, current can be discarded and candidate is still good */
+}
+
+static int match_sha(unsigned, const unsigned char *, const unsigned char *);
+
+static void find_short_object_filename(struct disambiguate_state *ds)
+{
+	struct object_directory *odb;
+
+	for (odb = ds->repo->objects->odb; odb && !ds->ambiguous; odb = odb->next) {
+		int pos;
+		struct oid_array *loose_objects;
+
+		loose_objects = odb_loose_cache(odb, &ds->bin_pfx);
+		pos = oid_array_lookup(loose_objects, &ds->bin_pfx);
+		if (pos < 0)
+			pos = -1 - pos;
+		while (!ds->ambiguous && pos < loose_objects->nr) {
+			const struct object_id *oid;
+			oid = loose_objects->oid + pos;
+			if (!match_sha(ds->len, ds->bin_pfx.hash, oid->hash))
+				break;
+			update_candidates(ds, oid);
+			pos++;
+		}
+	}
+}
+
+static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
+{
+	do {
+		if (*a != *b)
+			return 0;
+		a++;
+		b++;
+		len -= 2;
+	} while (len > 1);
+	if (len)
+		if ((*a ^ *b) & 0xf0)
+			return 0;
+	return 1;
+}
+
+static void unique_in_midx(struct multi_pack_index *m,
+			   struct disambiguate_state *ds)
+{
+	uint32_t num, i, first = 0;
+	const struct object_id *current = NULL;
+	num = m->num_objects;
+
+	if (!num)
+		return;
+
+	bsearch_midx(&ds->bin_pfx, m, &first);
+
+	/*
+	 * At this point, "first" is the location of the lowest object
+	 * with an object name that could match "bin_pfx".  See if we have
+	 * 0, 1 or more objects that actually match(es).
+	 */
+	for (i = first; i < num && !ds->ambiguous; i++) {
+		struct object_id oid;
+		current = nth_midxed_object_oid(&oid, m, i);
+		if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
+			break;
+		update_candidates(ds, current);
+	}
+}
+
+static void unique_in_pack(struct packed_git *p,
+			   struct disambiguate_state *ds)
+{
+	uint32_t num, i, first = 0;
+	const struct object_id *current = NULL;
+
+	if (p->multi_pack_index)
+		return;
+
+	if (open_pack_index(p) || !p->num_objects)
+		return;
+
+	num = p->num_objects;
+	bsearch_pack(&ds->bin_pfx, p, &first);
+
+	/*
+	 * At this point, "first" is the location of the lowest object
+	 * with an object name that could match "bin_pfx".  See if we have
+	 * 0, 1 or more objects that actually match(es).
+	 */
+	for (i = first; i < num && !ds->ambiguous; i++) {
+		struct object_id oid;
+		current = nth_packed_object_oid(&oid, p, i);
+		if (!match_sha(ds->len, ds->bin_pfx.hash, current->hash))
+			break;
+		update_candidates(ds, current);
+	}
+}
+
+static void find_short_packed_object(struct disambiguate_state *ds)
+{
+	struct multi_pack_index *m;
+	struct packed_git *p;
+
+	for (m = get_multi_pack_index(ds->repo); m && !ds->ambiguous;
+	     m = m->next)
+		unique_in_midx(m, ds);
+	for (p = get_packed_git(ds->repo); p && !ds->ambiguous;
+	     p = p->next)
+		unique_in_pack(p, ds);
+}
+
+static int finish_object_disambiguation(struct disambiguate_state *ds,
+					struct object_id *oid)
+{
+	if (ds->ambiguous)
+		return SHORT_NAME_AMBIGUOUS;
+
+	if (!ds->candidate_exists)
+		return MISSING_OBJECT;
+
+	if (!ds->candidate_checked)
+		/*
+		 * If this is the only candidate, there is no point
+		 * calling the disambiguation hint callback.
+		 *
+		 * On the other hand, if the current candidate
+		 * replaced an earlier candidate that did _not_ pass
+		 * the disambiguation hint callback, then we do have
+		 * more than one objects that match the short name
+		 * given, so we should make sure this one matches;
+		 * otherwise, if we discovered this one and the one
+		 * that we previously discarded in the reverse order,
+		 * we would end up showing different results in the
+		 * same repository!
+		 */
+		ds->candidate_ok = (!ds->disambiguate_fn_used ||
+				    ds->fn(ds->repo, &ds->candidate, ds->cb_data));
+
+	if (!ds->candidate_ok)
+		return SHORT_NAME_AMBIGUOUS;
+
+	oidcpy(oid, &ds->candidate);
+	return 0;
+}
+
+static int disambiguate_commit_only(struct repository *r,
+				    const struct object_id *oid,
+				    void *cb_data_unused)
+{
+	int kind = oid_object_info(r, oid, NULL);
+	return kind == OBJ_COMMIT;
+}
+
+static int disambiguate_committish_only(struct repository *r,
+					const struct object_id *oid,
+					void *cb_data_unused)
+{
+	struct object *obj;
+	int kind;
+
+	kind = oid_object_info(r, oid, NULL);
+	if (kind == OBJ_COMMIT)
+		return 1;
+	if (kind != OBJ_TAG)
+		return 0;
+
+	/* We need to do this the hard way... */
+	obj = deref_tag(r, parse_object(r, oid), NULL, 0);
+	if (obj && obj->type == OBJ_COMMIT)
+		return 1;
+	return 0;
+}
+
+static int disambiguate_tree_only(struct repository *r,
+				  const struct object_id *oid,
+				  void *cb_data_unused)
+{
+	int kind = oid_object_info(r, oid, NULL);
+	return kind == OBJ_TREE;
+}
+
+static int disambiguate_treeish_only(struct repository *r,
+				     const struct object_id *oid,
+				     void *cb_data_unused)
+{
+	struct object *obj;
+	int kind;
+
+	kind = oid_object_info(r, oid, NULL);
+	if (kind == OBJ_TREE || kind == OBJ_COMMIT)
+		return 1;
+	if (kind != OBJ_TAG)
+		return 0;
+
+	/* We need to do this the hard way... */
+	obj = deref_tag(r, parse_object(r, oid), NULL, 0);
+	if (obj && (obj->type == OBJ_TREE || obj->type == OBJ_COMMIT))
+		return 1;
+	return 0;
+}
+
+static int disambiguate_blob_only(struct repository *r,
+				  const struct object_id *oid,
+				  void *cb_data_unused)
+{
+	int kind = oid_object_info(r, oid, NULL);
+	return kind == OBJ_BLOB;
+}
+
+static disambiguate_hint_fn default_disambiguate_hint;
+
+int set_disambiguate_hint_config(const char *var, const char *value)
+{
+	static const struct {
+		const char *name;
+		disambiguate_hint_fn fn;
+	} hints[] = {
+		{ "none", NULL },
+		{ "commit", disambiguate_commit_only },
+		{ "committish", disambiguate_committish_only },
+		{ "tree", disambiguate_tree_only },
+		{ "treeish", disambiguate_treeish_only },
+		{ "blob", disambiguate_blob_only }
+	};
+	int i;
+
+	if (!value)
+		return config_error_nonbool(var);
+
+	for (i = 0; i < ARRAY_SIZE(hints); i++) {
+		if (!strcasecmp(value, hints[i].name)) {
+			default_disambiguate_hint = hints[i].fn;
+			return 0;
+		}
+	}
+
+	return error("unknown hint type for '%s': %s", var, value);
+}
+
+static int init_object_disambiguation(struct repository *r,
+				      const char *name, int len,
+				      struct disambiguate_state *ds)
+{
+	int i;
+
+	if (len < MINIMUM_ABBREV || len > the_hash_algo->hexsz)
+		return -1;
+
+	memset(ds, 0, sizeof(*ds));
+
+	for (i = 0; i < len ;i++) {
+		unsigned char c = name[i];
+		unsigned char val;
+		if (c >= '0' && c <= '9')
+			val = c - '0';
+		else if (c >= 'a' && c <= 'f')
+			val = c - 'a' + 10;
+		else if (c >= 'A' && c <='F') {
+			val = c - 'A' + 10;
+			c -= 'A' - 'a';
+		}
+		else
+			return -1;
+		ds->hex_pfx[i] = c;
+		if (!(i & 1))
+			val <<= 4;
+		ds->bin_pfx.hash[i >> 1] |= val;
+	}
+
+	ds->len = len;
+	ds->hex_pfx[len] = '\0';
+	ds->repo = r;
+	prepare_alt_odb(r);
+	return 0;
+}
+
+static int show_ambiguous_object(const struct object_id *oid, void *data)
+{
+	const struct disambiguate_state *ds = data;
+	struct strbuf desc = STRBUF_INIT;
+	int type;
+
+	if (ds->fn && !ds->fn(ds->repo, oid, ds->cb_data))
+		return 0;
+
+	type = oid_object_info(ds->repo, oid, NULL);
+	if (type == OBJ_COMMIT) {
+		struct commit *commit = lookup_commit(ds->repo, oid);
+		if (commit) {
+			struct pretty_print_context pp = {0};
+			pp.date_mode.type = DATE_SHORT;
+			format_commit_message(commit, " %ad - %s", &desc, &pp);
+		}
+	} else if (type == OBJ_TAG) {
+		struct tag *tag = lookup_tag(ds->repo, oid);
+		if (!parse_tag(tag) && tag->tag)
+			strbuf_addf(&desc, " %s", tag->tag);
+	}
+
+	advise("  %s %s%s",
+	       repo_find_unique_abbrev(ds->repo, oid, DEFAULT_ABBREV),
+	       type_name(type) ? type_name(type) : "unknown type",
+	       desc.buf);
+
+	strbuf_release(&desc);
+	return 0;
+}
+
+static int collect_ambiguous(const struct object_id *oid, void *data)
+{
+	oid_array_append(data, oid);
+	return 0;
+}
+
+static int repo_collect_ambiguous(struct repository *r,
+				  const struct object_id *oid,
+				  void *data)
+{
+	return collect_ambiguous(oid, data);
+}
+
+static struct repository *sort_ambiguous_repo;
+static int sort_ambiguous(const void *a, const void *b)
+{
+	int a_type = oid_object_info(sort_ambiguous_repo, a, NULL);
+	int b_type = oid_object_info(sort_ambiguous_repo, b, NULL);
+	int a_type_sort;
+	int b_type_sort;
+
+	/*
+	 * Sorts by hash within the same object type, just as
+	 * oid_array_for_each_unique() would do.
+	 */
+	if (a_type == b_type)
+		return oidcmp(a, b);
+
+	/*
+	 * Between object types show tags, then commits, and finally
+	 * trees and blobs.
+	 *
+	 * The object_type enum is commit, tree, blob, tag, but we
+	 * want tag, commit, tree blob. Cleverly (perhaps too
+	 * cleverly) do that with modulus, since the enum assigns 1 to
+	 * commit, so tag becomes 0.
+	 */
+	a_type_sort = a_type % 4;
+	b_type_sort = b_type % 4;
+	return a_type_sort > b_type_sort ? 1 : -1;
+}
+
+static void sort_ambiguous_oid_array(struct repository *r, struct oid_array *a)
+{
+	/* mutex will be needed if this code is to be made thread safe */
+	sort_ambiguous_repo = r;
+	QSORT(a->oid, a->nr, sort_ambiguous);
+	sort_ambiguous_repo = NULL;
+}
+
+static enum get_oid_result get_short_oid(struct repository *r,
+					 const char *name, int len,
+					 struct object_id *oid,
+					 unsigned flags)
+{
+	int status;
+	struct disambiguate_state ds;
+	int quietly = !!(flags & GET_OID_QUIETLY);
+
+	if (init_object_disambiguation(r, name, len, &ds) < 0)
+		return -1;
+
+	if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
+		BUG("multiple get_short_oid disambiguator flags");
+
+	if (flags & GET_OID_COMMIT)
+		ds.fn = disambiguate_commit_only;
+	else if (flags & GET_OID_COMMITTISH)
+		ds.fn = disambiguate_committish_only;
+	else if (flags & GET_OID_TREE)
+		ds.fn = disambiguate_tree_only;
+	else if (flags & GET_OID_TREEISH)
+		ds.fn = disambiguate_treeish_only;
+	else if (flags & GET_OID_BLOB)
+		ds.fn = disambiguate_blob_only;
+	else
+		ds.fn = default_disambiguate_hint;
+
+	find_short_object_filename(&ds);
+	find_short_packed_object(&ds);
+	status = finish_object_disambiguation(&ds, oid);
+
+	/*
+	 * If we didn't find it, do the usual reprepare() slow-path,
+	 * since the object may have recently been added to the repository
+	 * or migrated from loose to packed.
+	 */
+	if (status == MISSING_OBJECT) {
+		reprepare_packed_git(r);
+		find_short_object_filename(&ds);
+		find_short_packed_object(&ds);
+		status = finish_object_disambiguation(&ds, oid);
+	}
+
+	if (!quietly && (status == SHORT_NAME_AMBIGUOUS)) {
+		struct oid_array collect = OID_ARRAY_INIT;
+
+		error(_("short SHA1 %s is ambiguous"), ds.hex_pfx);
+
+		/*
+		 * We may still have ambiguity if we simply saw a series of
+		 * candidates that did not satisfy our hint function. In
+		 * that case, we still want to show them, so disable the hint
+		 * function entirely.
+		 */
+		if (!ds.ambiguous)
+			ds.fn = NULL;
+
+		advise(_("The candidates are:"));
+		repo_for_each_abbrev(r, ds.hex_pfx, collect_ambiguous, &collect);
+		sort_ambiguous_oid_array(r, &collect);
+
+		if (oid_array_for_each(&collect, show_ambiguous_object, &ds))
+			BUG("show_ambiguous_object shouldn't return non-zero");
+		oid_array_clear(&collect);
+	}
+
+	return status;
+}
+
+int repo_for_each_abbrev(struct repository *r, const char *prefix,
+			 each_abbrev_fn fn, void *cb_data)
+{
+	struct oid_array collect = OID_ARRAY_INIT;
+	struct disambiguate_state ds;
+	int ret;
+
+	if (init_object_disambiguation(r, prefix, strlen(prefix), &ds) < 0)
+		return -1;
+
+	ds.always_call_fn = 1;
+	ds.fn = repo_collect_ambiguous;
+	ds.cb_data = &collect;
+	find_short_object_filename(&ds);
+	find_short_packed_object(&ds);
+
+	ret = oid_array_for_each_unique(&collect, fn, cb_data);
+	oid_array_clear(&collect);
+	return ret;
+}
+
+/*
+ * Return the slot of the most-significant bit set in "val". There are various
+ * ways to do this quickly with fls() or __builtin_clzl(), but speed is
+ * probably not a big deal here.
+ */
+static unsigned msb(unsigned long val)
+{
+	unsigned r = 0;
+	while (val >>= 1)
+		r++;
+	return r;
+}
+
+struct min_abbrev_data {
+	unsigned int init_len;
+	unsigned int cur_len;
+	char *hex;
+	struct repository *repo;
+	const struct object_id *oid;
+};
+
+static inline char get_hex_char_from_oid(const struct object_id *oid,
+					 unsigned int pos)
+{
+	static const char hex[] = "0123456789abcdef";
+
+	if ((pos & 1) == 0)
+		return hex[oid->hash[pos >> 1] >> 4];
+	else
+		return hex[oid->hash[pos >> 1] & 0xf];
+}
+
+static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
+{
+	struct min_abbrev_data *mad = cb_data;
+
+	unsigned int i = mad->init_len;
+	while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
+		i++;
+
+	if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
+		mad->cur_len = i + 1;
+
+	return 0;
+}
+
+static int repo_extend_abbrev_len(struct repository *r,
+				  const struct object_id *oid,
+				  void *cb_data)
+{
+	return extend_abbrev_len(oid, cb_data);
+}
+
+static void find_abbrev_len_for_midx(struct multi_pack_index *m,
+				     struct min_abbrev_data *mad)
+{
+	int match = 0;
+	uint32_t num, first = 0;
+	struct object_id oid;
+	const struct object_id *mad_oid;
+
+	if (!m->num_objects)
+		return;
+
+	num = m->num_objects;
+	mad_oid = mad->oid;
+	match = bsearch_midx(mad_oid, m, &first);
+
+	/*
+	 * first is now the position in the packfile where we would insert
+	 * mad->hash if it does not exist (or the position of mad->hash if
+	 * it does exist). Hence, we consider a maximum of two objects
+	 * nearby for the abbreviation length.
+	 */
+	mad->init_len = 0;
+	if (!match) {
+		if (nth_midxed_object_oid(&oid, m, first))
+			extend_abbrev_len(&oid, mad);
+	} else if (first < num - 1) {
+		if (nth_midxed_object_oid(&oid, m, first + 1))
+			extend_abbrev_len(&oid, mad);
+	}
+	if (first > 0) {
+		if (nth_midxed_object_oid(&oid, m, first - 1))
+			extend_abbrev_len(&oid, mad);
+	}
+	mad->init_len = mad->cur_len;
+}
+
+static void find_abbrev_len_for_pack(struct packed_git *p,
+				     struct min_abbrev_data *mad)
+{
+	int match = 0;
+	uint32_t num, first = 0;
+	struct object_id oid;
+	const struct object_id *mad_oid;
+
+	if (p->multi_pack_index)
+		return;
+
+	if (open_pack_index(p) || !p->num_objects)
+		return;
+
+	num = p->num_objects;
+	mad_oid = mad->oid;
+	match = bsearch_pack(mad_oid, p, &first);
+
+	/*
+	 * first is now the position in the packfile where we would insert
+	 * mad->hash if it does not exist (or the position of mad->hash if
+	 * it does exist). Hence, we consider a maximum of two objects
+	 * nearby for the abbreviation length.
+	 */
+	mad->init_len = 0;
+	if (!match) {
+		if (nth_packed_object_oid(&oid, p, first))
+			extend_abbrev_len(&oid, mad);
+	} else if (first < num - 1) {
+		if (nth_packed_object_oid(&oid, p, first + 1))
+			extend_abbrev_len(&oid, mad);
+	}
+	if (first > 0) {
+		if (nth_packed_object_oid(&oid, p, first - 1))
+			extend_abbrev_len(&oid, mad);
+	}
+	mad->init_len = mad->cur_len;
+}
+
+static void find_abbrev_len_packed(struct min_abbrev_data *mad)
+{
+	struct multi_pack_index *m;
+	struct packed_git *p;
+
+	for (m = get_multi_pack_index(mad->repo); m; m = m->next)
+		find_abbrev_len_for_midx(m, mad);
+	for (p = get_packed_git(mad->repo); p; p = p->next)
+		find_abbrev_len_for_pack(p, mad);
+}
+
+int repo_find_unique_abbrev_r(struct repository *r, char *hex,
+			      const struct object_id *oid, int len)
+{
+	struct disambiguate_state ds;
+	struct min_abbrev_data mad;
+	struct object_id oid_ret;
+	const unsigned hexsz = r->hash_algo->hexsz;
+
+	if (len < 0) {
+		unsigned long count = repo_approximate_object_count(r);
+		/*
+		 * Add one because the MSB only tells us the highest bit set,
+		 * not including the value of all the _other_ bits (so "15"
+		 * is only one off of 2^4, but the MSB is the 3rd bit.
+		 */
+		len = msb(count) + 1;
+		/*
+		 * We now know we have on the order of 2^len objects, which
+		 * expects a collision at 2^(len/2). But we also care about hex
+		 * chars, not bits, and there are 4 bits per hex. So all
+		 * together we need to divide by 2 and round up.
+		 */
+		len = DIV_ROUND_UP(len, 2);
+		/*
+		 * For very small repos, we stick with our regular fallback.
+		 */
+		if (len < FALLBACK_DEFAULT_ABBREV)
+			len = FALLBACK_DEFAULT_ABBREV;
+	}
+
+	oid_to_hex_r(hex, oid);
+	if (len == hexsz || !len)
+		return hexsz;
+
+	mad.repo = r;
+	mad.init_len = len;
+	mad.cur_len = len;
+	mad.hex = hex;
+	mad.oid = oid;
+
+	find_abbrev_len_packed(&mad);
+
+	if (init_object_disambiguation(r, hex, mad.cur_len, &ds) < 0)
+		return -1;
+
+	ds.fn = repo_extend_abbrev_len;
+	ds.always_call_fn = 1;
+	ds.cb_data = (void *)&mad;
+
+	find_short_object_filename(&ds);
+	(void)finish_object_disambiguation(&ds, &oid_ret);
+
+	hex[mad.cur_len] = 0;
+	return mad.cur_len;
+}
+
+const char *repo_find_unique_abbrev(struct repository *r,
+				    const struct object_id *oid,
+				    int len)
+{
+	static int bufno;
+	static char hexbuffer[4][GIT_MAX_HEXSZ + 1];
+	char *hex = hexbuffer[bufno];
+	bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
+	repo_find_unique_abbrev_r(r, hex, oid, len);
+	return hex;
+}
+
+static int ambiguous_path(const char *path, int len)
+{
+	int slash = 1;
+	int cnt;
+
+	for (cnt = 0; cnt < len; cnt++) {
+		switch (*path++) {
+		case '\0':
+			break;
+		case '/':
+			if (slash)
+				break;
+			slash = 1;
+			continue;
+		case '.':
+			continue;
+		default:
+			slash = 0;
+			continue;
+		}
+		break;
+	}
+	return slash;
+}
+
+static inline int at_mark(const char *string, int len,
+			  const char **suffix, int nr)
+{
+	int i;
+
+	for (i = 0; i < nr; i++) {
+		int suffix_len = strlen(suffix[i]);
+		if (suffix_len <= len
+		    && !strncasecmp(string, suffix[i], suffix_len))
+			return suffix_len;
+	}
+	return 0;
+}
+
+static inline int upstream_mark(const char *string, int len)
+{
+	const char *suffix[] = { "@{upstream}", "@{u}" };
+	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
+}
+
+static inline int push_mark(const char *string, int len)
+{
+	const char *suffix[] = { "@{push}" };
+	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
+}
+
+static enum get_oid_result get_oid_1(struct repository *r, const char *name, int len, struct object_id *oid, unsigned lookup_flags);
+static int interpret_nth_prior_checkout(struct repository *r, const char *name, int namelen, struct strbuf *buf);
+
+static int get_oid_basic(struct repository *r, const char *str, int len,
+			 struct object_id *oid, unsigned int flags)
+{
+	static const char *warn_msg = "refname '%.*s' is ambiguous.";
+	static const char *object_name_msg = N_(
+	"Git normally never creates a ref that ends with 40 hex characters\n"
+	"because it will be ignored when you just specify 40-hex. These refs\n"
+	"may be created by mistake. For example,\n"
+	"\n"
+	"  git switch -c $br $(git rev-parse ...)\n"
+	"\n"
+	"where \"$br\" is somehow empty and a 40-hex ref is created. Please\n"
+	"examine these refs and maybe delete them. Turn this message off by\n"
+	"running \"git config advice.objectNameWarning false\"");
+	struct object_id tmp_oid;
+	char *real_ref = NULL;
+	int refs_found = 0;
+	int at, reflog_len, nth_prior = 0;
+
+	if (len == r->hash_algo->hexsz && !get_oid_hex(str, oid)) {
+		if (warn_ambiguous_refs && warn_on_object_refname_ambiguity) {
+			refs_found = repo_dwim_ref(r, str, len, &tmp_oid, &real_ref);
+			if (refs_found > 0) {
+				warning(warn_msg, len, str);
+				if (advice_object_name_warning)
+					fprintf(stderr, "%s\n", _(object_name_msg));
+			}
+			free(real_ref);
+		}
+		return 0;
+	}
+
+	/* basic@{time or number or -number} format to query ref-log */
+	reflog_len = at = 0;
+	if (len && str[len-1] == '}') {
+		for (at = len-4; at >= 0; at--) {
+			if (str[at] == '@' && str[at+1] == '{') {
+				if (str[at+2] == '-') {
+					if (at != 0)
+						/* @{-N} not at start */
+						return -1;
+					nth_prior = 1;
+					continue;
+				}
+				if (!upstream_mark(str + at, len - at) &&
+				    !push_mark(str + at, len - at)) {
+					reflog_len = (len-1) - (at+2);
+					len = at;
+				}
+				break;
+			}
+		}
+	}
+
+	/* Accept only unambiguous ref paths. */
+	if (len && ambiguous_path(str, len))
+		return -1;
+
+	if (nth_prior) {
+		struct strbuf buf = STRBUF_INIT;
+		int detached;
+
+		if (interpret_nth_prior_checkout(r, str, len, &buf) > 0) {
+			detached = (buf.len == r->hash_algo->hexsz && !get_oid_hex(buf.buf, oid));
+			strbuf_release(&buf);
+			if (detached)
+				return 0;
+		}
+	}
+
+	if (!len && reflog_len)
+		/* allow "@{...}" to mean the current branch reflog */
+		refs_found = repo_dwim_ref(r, "HEAD", 4, oid, &real_ref);
+	else if (reflog_len)
+		refs_found = repo_dwim_log(r, str, len, oid, &real_ref);
+	else
+		refs_found = repo_dwim_ref(r, str, len, oid, &real_ref);
+
+	if (!refs_found)
+		return -1;
+
+	if (warn_ambiguous_refs && !(flags & GET_OID_QUIETLY) &&
+	    (refs_found > 1 ||
+	     !get_short_oid(r, str, len, &tmp_oid, GET_OID_QUIETLY)))
+		warning(warn_msg, len, str);
+
+	if (reflog_len) {
+		int nth, i;
+		timestamp_t at_time;
+		timestamp_t co_time;
+		int co_tz, co_cnt;
+
+		/* Is it asking for N-th entry, or approxidate? */
+		for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
+			char ch = str[at+2+i];
+			if ('0' <= ch && ch <= '9')
+				nth = nth * 10 + ch - '0';
+			else
+				nth = -1;
+		}
+		if (100000000 <= nth) {
+			at_time = nth;
+			nth = -1;
+		} else if (0 <= nth)
+			at_time = 0;
+		else {
+			int errors = 0;
+			char *tmp = xstrndup(str + at + 2, reflog_len);
+			at_time = approxidate_careful(tmp, &errors);
+			free(tmp);
+			if (errors) {
+				free(real_ref);
+				return -1;
+			}
+		}
+		if (read_ref_at(get_main_ref_store(r),
+				real_ref, flags, at_time, nth, oid, NULL,
+				&co_time, &co_tz, &co_cnt)) {
+			if (!len) {
+				if (starts_with(real_ref, "refs/heads/")) {
+					str = real_ref + 11;
+					len = strlen(real_ref + 11);
+				} else {
+					/* detached HEAD */
+					str = "HEAD";
+					len = 4;
+				}
+			}
+			if (at_time) {
+				if (!(flags & GET_OID_QUIETLY)) {
+					warning("Log for '%.*s' only goes "
+						"back to %s.", len, str,
+						show_date(co_time, co_tz, DATE_MODE(RFC2822)));
+				}
+			} else {
+				if (flags & GET_OID_QUIETLY) {
+					exit(128);
+				}
+				die("Log for '%.*s' only has %d entries.",
+				    len, str, co_cnt);
+			}
+		}
+	}
+
+	free(real_ref);
+	return 0;
+}
+
+static enum get_oid_result get_parent(struct repository *r,
+				      const char *name, int len,
+				      struct object_id *result, int idx)
+{
+	struct object_id oid;
+	enum get_oid_result ret = get_oid_1(r, name, len, &oid,
+					    GET_OID_COMMITTISH);
+	struct commit *commit;
+	struct commit_list *p;
+
+	if (ret)
+		return ret;
+	commit = lookup_commit_reference(r, &oid);
+	if (parse_commit(commit))
+		return MISSING_OBJECT;
+	if (!idx) {
+		oidcpy(result, &commit->object.oid);
+		return FOUND;
+	}
+	p = commit->parents;
+	while (p) {
+		if (!--idx) {
+			oidcpy(result, &p->item->object.oid);
+			return FOUND;
+		}
+		p = p->next;
+	}
+	return MISSING_OBJECT;
+}
+
+static enum get_oid_result get_nth_ancestor(struct repository *r,
+					    const char *name, int len,
+					    struct object_id *result,
+					    int generation)
+{
+	struct object_id oid;
+	struct commit *commit;
+	int ret;
+
+	ret = get_oid_1(r, name, len, &oid, GET_OID_COMMITTISH);
+	if (ret)
+		return ret;
+	commit = lookup_commit_reference(r, &oid);
+	if (!commit)
+		return MISSING_OBJECT;
+
+	while (generation--) {
+		if (parse_commit(commit) || !commit->parents)
+			return MISSING_OBJECT;
+		commit = commit->parents->item;
+	}
+	oidcpy(result, &commit->object.oid);
+	return FOUND;
+}
+
+struct object *repo_peel_to_type(struct repository *r, const char *name, int namelen,
+				 struct object *o, enum object_type expected_type)
+{
+	if (name && !namelen)
+		namelen = strlen(name);
+	while (1) {
+		if (!o || (!o->parsed && !parse_object(r, &o->oid)))
+			return NULL;
+		if (expected_type == OBJ_ANY || o->type == expected_type)
+			return o;
+		if (o->type == OBJ_TAG)
+			o = ((struct tag*) o)->tagged;
+		else if (o->type == OBJ_COMMIT)
+			o = &(repo_get_commit_tree(r, ((struct commit *)o))->object);
+		else {
+			if (name)
+				error("%.*s: expected %s type, but the object "
+				      "dereferences to %s type",
+				      namelen, name, type_name(expected_type),
+				      type_name(o->type));
+			return NULL;
+		}
+	}
+}
+
+static int peel_onion(struct repository *r, const char *name, int len,
+		      struct object_id *oid, unsigned lookup_flags)
+{
+	struct object_id outer;
+	const char *sp;
+	unsigned int expected_type = 0;
+	struct object *o;
+
+	/*
+	 * "ref^{type}" dereferences ref repeatedly until you cannot
+	 * dereference anymore, or you get an object of given type,
+	 * whichever comes first.  "ref^{}" means just dereference
+	 * tags until you get a non-tag.  "ref^0" is a shorthand for
+	 * "ref^{commit}".  "commit^{tree}" could be used to find the
+	 * top-level tree of the given commit.
+	 */
+	if (len < 4 || name[len-1] != '}')
+		return -1;
+
+	for (sp = name + len - 1; name <= sp; sp--) {
+		int ch = *sp;
+		if (ch == '{' && name < sp && sp[-1] == '^')
+			break;
+	}
+	if (sp <= name)
+		return -1;
+
+	sp++; /* beginning of type name, or closing brace for empty */
+	if (starts_with(sp, "commit}"))
+		expected_type = OBJ_COMMIT;
+	else if (starts_with(sp, "tag}"))
+		expected_type = OBJ_TAG;
+	else if (starts_with(sp, "tree}"))
+		expected_type = OBJ_TREE;
+	else if (starts_with(sp, "blob}"))
+		expected_type = OBJ_BLOB;
+	else if (starts_with(sp, "object}"))
+		expected_type = OBJ_ANY;
+	else if (sp[0] == '}')
+		expected_type = OBJ_NONE;
+	else if (sp[0] == '/')
+		expected_type = OBJ_COMMIT;
+	else
+		return -1;
+
+	lookup_flags &= ~GET_OID_DISAMBIGUATORS;
+	if (expected_type == OBJ_COMMIT)
+		lookup_flags |= GET_OID_COMMITTISH;
+	else if (expected_type == OBJ_TREE)
+		lookup_flags |= GET_OID_TREEISH;
+
+	if (get_oid_1(r, name, sp - name - 2, &outer, lookup_flags))
+		return -1;
+
+	o = parse_object(r, &outer);
+	if (!o)
+		return -1;
+	if (!expected_type) {
+		o = deref_tag(r, o, name, sp - name - 2);
+		if (!o || (!o->parsed && !parse_object(r, &o->oid)))
+			return -1;
+		oidcpy(oid, &o->oid);
+		return 0;
+	}
+
+	/*
+	 * At this point, the syntax look correct, so
+	 * if we do not get the needed object, we should
+	 * barf.
+	 */
+	o = repo_peel_to_type(r, name, len, o, expected_type);
+	if (!o)
+		return -1;
+
+	oidcpy(oid, &o->oid);
+	if (sp[0] == '/') {
+		/* "$commit^{/foo}" */
+		char *prefix;
+		int ret;
+		struct commit_list *list = NULL;
+
+		/*
+		 * $commit^{/}. Some regex implementation may reject.
+		 * We don't need regex anyway. '' pattern always matches.
+		 */
+		if (sp[1] == '}')
+			return 0;
+
+		prefix = xstrndup(sp + 1, name + len - 1 - (sp + 1));
+		commit_list_insert((struct commit *)o, &list);
+		ret = get_oid_oneline(r, prefix, oid, list);
+		free(prefix);
+		return ret;
+	}
+	return 0;
+}
+
+static int get_describe_name(struct repository *r,
+			     const char *name, int len,
+			     struct object_id *oid)
+{
+	const char *cp;
+	unsigned flags = GET_OID_QUIETLY | GET_OID_COMMIT;
+
+	for (cp = name + len - 1; name + 2 <= cp; cp--) {
+		char ch = *cp;
+		if (!isxdigit(ch)) {
+			/* We must be looking at g in "SOMETHING-g"
+			 * for it to be describe output.
+			 */
+			if (ch == 'g' && cp[-1] == '-') {
+				cp++;
+				len -= cp - name;
+				return get_short_oid(r,
+						     cp, len, oid, flags);
+			}
+		}
+	}
+	return -1;
+}
+
+static enum get_oid_result get_oid_1(struct repository *r,
+				     const char *name, int len,
+				     struct object_id *oid,
+				     unsigned lookup_flags)
+{
+	int ret, has_suffix;
+	const char *cp;
+
+	/*
+	 * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
+	 */
+	has_suffix = 0;
+	for (cp = name + len - 1; name <= cp; cp--) {
+		int ch = *cp;
+		if ('0' <= ch && ch <= '9')
+			continue;
+		if (ch == '~' || ch == '^')
+			has_suffix = ch;
+		break;
+	}
+
+	if (has_suffix) {
+		int num = 0;
+		int len1 = cp - name;
+		cp++;
+		while (cp < name + len)
+			num = num * 10 + *cp++ - '0';
+		if (!num && len1 == len - 1)
+			num = 1;
+		if (has_suffix == '^')
+			return get_parent(r, name, len1, oid, num);
+		/* else if (has_suffix == '~') -- goes without saying */
+		return get_nth_ancestor(r, name, len1, oid, num);
+	}
+
+	ret = peel_onion(r, name, len, oid, lookup_flags);
+	if (!ret)
+		return FOUND;
+
+	ret = get_oid_basic(r, name, len, oid, lookup_flags);
+	if (!ret)
+		return FOUND;
+
+	/* It could be describe output that is "SOMETHING-gXXXX" */
+	ret = get_describe_name(r, name, len, oid);
+	if (!ret)
+		return FOUND;
+
+	return get_short_oid(r, name, len, oid, lookup_flags);
+}
+
+/*
+ * This interprets names like ':/Initial revision of "git"' by searching
+ * through history and returning the first commit whose message starts
+ * the given regular expression.
+ *
+ * For negative-matching, prefix the pattern-part with '!-', like: ':/!-WIP'.
+ *
+ * For a literal '!' character at the beginning of a pattern, you have to repeat
+ * that, like: ':/!!foo'
+ *
+ * For future extension, all other sequences beginning with ':/!' are reserved.
+ */
+
+/* Remember to update object flag allocation in object.h */
+#define ONELINE_SEEN (1u<<20)
+
+struct handle_one_ref_cb {
+	struct repository *repo;
+	struct commit_list **list;
+};
+
+static int handle_one_ref(const char *path, const struct object_id *oid,
+			  int flag, void *cb_data)
+{
+	struct handle_one_ref_cb *cb = cb_data;
+	struct commit_list **list = cb->list;
+	struct object *object = parse_object(cb->repo, oid);
+	if (!object)
+		return 0;
+	if (object->type == OBJ_TAG) {
+		object = deref_tag(cb->repo, object, path,
+				   strlen(path));
+		if (!object)
+			return 0;
+	}
+	if (object->type != OBJ_COMMIT)
+		return 0;
+	commit_list_insert((struct commit *)object, list);
+	return 0;
+}
+
+static int get_oid_oneline(struct repository *r,
+			   const char *prefix, struct object_id *oid,
+			   struct commit_list *list)
+{
+	struct commit_list *backup = NULL, *l;
+	int found = 0;
+	int negative = 0;
+	regex_t regex;
+
+	if (prefix[0] == '!') {
+		prefix++;
+
+		if (prefix[0] == '-') {
+			prefix++;
+			negative = 1;
+		} else if (prefix[0] != '!') {
+			return -1;
+		}
+	}
+
+	if (regcomp(&regex, prefix, REG_EXTENDED))
+		return -1;
+
+	for (l = list; l; l = l->next) {
+		l->item->object.flags |= ONELINE_SEEN;
+		commit_list_insert(l->item, &backup);
+	}
+	while (list) {
+		const char *p, *buf;
+		struct commit *commit;
+		int matches;
+
+		commit = pop_most_recent_commit(&list, ONELINE_SEEN);
+		if (!parse_object(r, &commit->object.oid))
+			continue;
+		buf = get_commit_buffer(commit, NULL);
+		p = strstr(buf, "\n\n");
+		matches = negative ^ (p && !regexec(&regex, p + 2, 0, NULL, 0));
+		unuse_commit_buffer(commit, buf);
+
+		if (matches) {
+			oidcpy(oid, &commit->object.oid);
+			found = 1;
+			break;
+		}
+	}
+	regfree(&regex);
+	free_commit_list(list);
+	for (l = backup; l; l = l->next)
+		clear_commit_marks(l->item, ONELINE_SEEN);
+	free_commit_list(backup);
+	return found ? 0 : -1;
+}
+
+struct grab_nth_branch_switch_cbdata {
+	int remaining;
+	struct strbuf buf;
+};
+
+static int grab_nth_branch_switch(struct object_id *ooid, struct object_id *noid,
+				  const char *email, timestamp_t timestamp, int tz,
+				  const char *message, void *cb_data)
+{
+	struct grab_nth_branch_switch_cbdata *cb = cb_data;
+	const char *match = NULL, *target = NULL;
+	size_t len;
+
+	if (skip_prefix(message, "checkout: moving from ", &match))
+		target = strstr(match, " to ");
+
+	if (!match || !target)
+		return 0;
+	if (--(cb->remaining) == 0) {
+		len = target - match;
+		strbuf_reset(&cb->buf);
+		strbuf_add(&cb->buf, match, len);
+		return 1; /* we are done */
+	}
+	return 0;
+}
+
+/*
+ * Parse @{-N} syntax, return the number of characters parsed
+ * if successful; otherwise signal an error with negative value.
+ */
+static int interpret_nth_prior_checkout(struct repository *r,
+					const char *name, int namelen,
+					struct strbuf *buf)
+{
+	long nth;
+	int retval;
+	struct grab_nth_branch_switch_cbdata cb;
+	const char *brace;
+	char *num_end;
+
+	if (namelen < 4)
+		return -1;
+	if (name[0] != '@' || name[1] != '{' || name[2] != '-')
+		return -1;
+	brace = memchr(name, '}', namelen);
+	if (!brace)
+		return -1;
+	nth = strtol(name + 3, &num_end, 10);
+	if (num_end != brace)
+		return -1;
+	if (nth <= 0)
+		return -1;
+	cb.remaining = nth;
+	strbuf_init(&cb.buf, 20);
+
+	retval = refs_for_each_reflog_ent_reverse(get_main_ref_store(r),
+			"HEAD", grab_nth_branch_switch, &cb);
+	if (0 < retval) {
+		strbuf_reset(buf);
+		strbuf_addbuf(buf, &cb.buf);
+		retval = brace - name + 1;
+	} else
+		retval = 0;
+
+	strbuf_release(&cb.buf);
+	return retval;
+}
+
+int repo_get_oid_mb(struct repository *r,
+		    const char *name,
+		    struct object_id *oid)
+{
+	struct commit *one, *two;
+	struct commit_list *mbs;
+	struct object_id oid_tmp;
+	const char *dots;
+	int st;
+
+	dots = strstr(name, "...");
+	if (!dots)
+		return repo_get_oid(r, name, oid);
+	if (dots == name)
+		st = repo_get_oid(r, "HEAD", &oid_tmp);
+	else {
+		struct strbuf sb;
+		strbuf_init(&sb, dots - name);
+		strbuf_add(&sb, name, dots - name);
+		st = repo_get_oid_committish(r, sb.buf, &oid_tmp);
+		strbuf_release(&sb);
+	}
+	if (st)
+		return st;
+	one = lookup_commit_reference_gently(r, &oid_tmp, 0);
+	if (!one)
+		return -1;
+
+	if (repo_get_oid_committish(r, dots[3] ? (dots + 3) : "HEAD", &oid_tmp))
+		return -1;
+	two = lookup_commit_reference_gently(r, &oid_tmp, 0);
+	if (!two)
+		return -1;
+	mbs = repo_get_merge_bases(r, one, two);
+	if (!mbs || mbs->next)
+		st = -1;
+	else {
+		st = 0;
+		oidcpy(oid, &mbs->item->object.oid);
+	}
+	free_commit_list(mbs);
+	return st;
+}
+
+/* parse @something syntax, when 'something' is not {.*} */
+static int interpret_empty_at(const char *name, int namelen, int len, struct strbuf *buf)
+{
+	const char *next;
+
+	if (len || name[1] == '{')
+		return -1;
+
+	/* make sure it's a single @, or @@{.*}, not @foo */
+	next = memchr(name + len + 1, '@', namelen - len - 1);
+	if (next && next[1] != '{')
+		return -1;
+	if (!next)
+		next = name + namelen;
+	if (next != name + 1)
+		return -1;
+
+	strbuf_reset(buf);
+	strbuf_add(buf, "HEAD", 4);
+	return 1;
+}
+
+static int reinterpret(struct repository *r,
+		       const char *name, int namelen, int len,
+		       struct strbuf *buf, unsigned allowed)
+{
+	/* we have extra data, which might need further processing */
+	struct strbuf tmp = STRBUF_INIT;
+	int used = buf->len;
+	int ret;
+
+	strbuf_add(buf, name + len, namelen - len);
+	ret = repo_interpret_branch_name(r, buf->buf, buf->len, &tmp, allowed);
+	/* that data was not interpreted, remove our cruft */
+	if (ret < 0) {
+		strbuf_setlen(buf, used);
+		return len;
+	}
+	strbuf_reset(buf);
+	strbuf_addbuf(buf, &tmp);
+	strbuf_release(&tmp);
+	/* tweak for size of {-N} versus expanded ref name */
+	return ret - used + len;
+}
+
+static void set_shortened_ref(struct repository *r, struct strbuf *buf, const char *ref)
+{
+	char *s = refs_shorten_unambiguous_ref(get_main_ref_store(r), ref, 0);
+	strbuf_reset(buf);
+	strbuf_addstr(buf, s);
+	free(s);
+}
+
+static int branch_interpret_allowed(const char *refname, unsigned allowed)
+{
+	if (!allowed)
+		return 1;
+
+	if ((allowed & INTERPRET_BRANCH_LOCAL) &&
+	    starts_with(refname, "refs/heads/"))
+		return 1;
+	if ((allowed & INTERPRET_BRANCH_REMOTE) &&
+	    starts_with(refname, "refs/remotes/"))
+		return 1;
+
+	return 0;
+}
+
+static int interpret_branch_mark(struct repository *r,
+				 const char *name, int namelen,
+				 int at, struct strbuf *buf,
+				 int (*get_mark)(const char *, int),
+				 const char *(*get_data)(struct branch *,
+							 struct strbuf *),
+				 unsigned allowed)
+{
+	int len;
+	struct branch *branch;
+	struct strbuf err = STRBUF_INIT;
+	const char *value;
+
+	len = get_mark(name + at, namelen - at);
+	if (!len)
+		return -1;
+
+	if (memchr(name, ':', at))
+		return -1;
+
+	if (at) {
+		char *name_str = xmemdupz(name, at);
+		branch = branch_get(name_str);
+		free(name_str);
+	} else
+		branch = branch_get(NULL);
+
+	value = get_data(branch, &err);
+	if (!value)
+		die("%s", err.buf);
+
+	if (!branch_interpret_allowed(value, allowed))
+		return -1;
+
+	set_shortened_ref(r, buf, value);
+	return len + at;
+}
+
+int repo_interpret_branch_name(struct repository *r,
+			       const char *name, int namelen,
+			       struct strbuf *buf,
+			       unsigned allowed)
+{
+	char *at;
+	const char *start;
+	int len;
+
+	if (!namelen)
+		namelen = strlen(name);
+
+	if (!allowed || (allowed & INTERPRET_BRANCH_LOCAL)) {
+		len = interpret_nth_prior_checkout(r, name, namelen, buf);
+		if (!len) {
+			return len; /* syntax Ok, not enough switches */
+		} else if (len > 0) {
+			if (len == namelen)
+				return len; /* consumed all */
+			else
+				return reinterpret(r, name, namelen, len, buf, allowed);
+		}
+	}
+
+	for (start = name;
+	     (at = memchr(start, '@', namelen - (start - name)));
+	     start = at + 1) {
+
+		if (!allowed || (allowed & INTERPRET_BRANCH_HEAD)) {
+			len = interpret_empty_at(name, namelen, at - name, buf);
+			if (len > 0)
+				return reinterpret(r, name, namelen, len, buf,
+						   allowed);
+		}
+
+		len = interpret_branch_mark(r, name, namelen, at - name, buf,
+					    upstream_mark, branch_get_upstream,
+					    allowed);
+		if (len > 0)
+			return len;
+
+		len = interpret_branch_mark(r, name, namelen, at - name, buf,
+					    push_mark, branch_get_push,
+					    allowed);
+		if (len > 0)
+			return len;
+	}
+
+	return -1;
+}
+
+void strbuf_branchname(struct strbuf *sb, const char *name, unsigned allowed)
+{
+	int len = strlen(name);
+	int used = interpret_branch_name(name, len, sb, allowed);
+
+	if (used < 0)
+		used = 0;
+	strbuf_add(sb, name + used, len - used);
+}
+
+int strbuf_check_branch_ref(struct strbuf *sb, const char *name)
+{
+	if (startup_info->have_repository)
+		strbuf_branchname(sb, name, INTERPRET_BRANCH_LOCAL);
+	else
+		strbuf_addstr(sb, name);
+
+	/*
+	 * This splice must be done even if we end up rejecting the
+	 * name; builtin/branch.c::copy_or_rename_branch() still wants
+	 * to see what the name expanded to so that "branch -m" can be
+	 * used as a tool to correct earlier mistakes.
+	 */
+	strbuf_splice(sb, 0, 0, "refs/heads/", 11);
+
+	if (*name == '-' ||
+	    !strcmp(sb->buf, "refs/heads/HEAD"))
+		return -1;
+
+	return check_refname_format(sb->buf, 0);
+}
+
+/*
+ * This is like "get_oid_basic()", except it allows "object ID expressions",
+ * notably "xyz^" for "parent of xyz"
+ */
+int repo_get_oid(struct repository *r, const char *name, struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, 0, oid, &unused);
+}
+
+/*
+ * This returns a non-zero value if the string (built using printf
+ * format and the given arguments) is not a valid object.
+ */
+int get_oidf(struct object_id *oid, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+	struct strbuf sb = STRBUF_INIT;
+
+	va_start(ap, fmt);
+	strbuf_vaddf(&sb, fmt, ap);
+	va_end(ap);
+
+	ret = get_oid(sb.buf, oid);
+	strbuf_release(&sb);
+
+	return ret;
+}
+
+/*
+ * Many callers know that the user meant to name a commit-ish by
+ * syntactical positions where the object name appears.  Calling this
+ * function allows the machinery to disambiguate shorter-than-unique
+ * abbreviated object names between commit-ish and others.
+ *
+ * Note that this does NOT error out when the named object is not a
+ * commit-ish. It is merely to give a hint to the disambiguation
+ * machinery.
+ */
+int repo_get_oid_committish(struct repository *r,
+			    const char *name,
+			    struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, GET_OID_COMMITTISH,
+				    oid, &unused);
+}
+
+int repo_get_oid_treeish(struct repository *r,
+			 const char *name,
+			 struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, GET_OID_TREEISH,
+				    oid, &unused);
+}
+
+int repo_get_oid_commit(struct repository *r,
+			const char *name,
+			struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, GET_OID_COMMIT,
+				    oid, &unused);
+}
+
+int repo_get_oid_tree(struct repository *r,
+		      const char *name,
+		      struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, GET_OID_TREE,
+				    oid, &unused);
+}
+
+int repo_get_oid_blob(struct repository *r,
+		      const char *name,
+		      struct object_id *oid)
+{
+	struct object_context unused;
+	return get_oid_with_context(r, name, GET_OID_BLOB,
+				    oid, &unused);
+}
+
+/* Must be called only when object_name:filename doesn't exist. */
+static void diagnose_invalid_oid_path(struct repository *r,
+				      const char *prefix,
+				      const char *filename,
+				      const struct object_id *tree_oid,
+				      const char *object_name,
+				      int object_name_len)
+{
+	struct object_id oid;
+	unsigned short mode;
+
+	if (!prefix)
+		prefix = "";
+
+	if (file_exists(filename))
+		die("Path '%s' exists on disk, but not in '%.*s'.",
+		    filename, object_name_len, object_name);
+	if (is_missing_file_error(errno)) {
+		char *fullname = xstrfmt("%s%s", prefix, filename);
+
+		if (!get_tree_entry(r, tree_oid, fullname, &oid, &mode)) {
+			die("Path '%s' exists, but not '%s'.\n"
+			    "Did you mean '%.*s:%s' aka '%.*s:./%s'?",
+			    fullname,
+			    filename,
+			    object_name_len, object_name,
+			    fullname,
+			    object_name_len, object_name,
+			    filename);
+		}
+		die("Path '%s' does not exist in '%.*s'",
+		    filename, object_name_len, object_name);
+	}
+}
+
+/* Must be called only when :stage:filename doesn't exist. */
+static void diagnose_invalid_index_path(struct repository *r,
+					int stage,
+					const char *prefix,
+					const char *filename)
+{
+	struct index_state *istate = r->index;
+	const struct cache_entry *ce;
+	int pos;
+	unsigned namelen = strlen(filename);
+	struct strbuf fullname = STRBUF_INIT;
+
+	if (!prefix)
+		prefix = "";
+
+	/* Wrong stage number? */
+	pos = index_name_pos(istate, filename, namelen);
+	if (pos < 0)
+		pos = -pos - 1;
+	if (pos < istate->cache_nr) {
+		ce = istate->cache[pos];
+		if (ce_namelen(ce) == namelen &&
+		    !memcmp(ce->name, filename, namelen))
+			die("Path '%s' is in the index, but not at stage %d.\n"
+			    "Did you mean ':%d:%s'?",
+			    filename, stage,
+			    ce_stage(ce), filename);
+	}
+
+	/* Confusion between relative and absolute filenames? */
+	strbuf_addstr(&fullname, prefix);
+	strbuf_addstr(&fullname, filename);
+	pos = index_name_pos(istate, fullname.buf, fullname.len);
+	if (pos < 0)
+		pos = -pos - 1;
+	if (pos < istate->cache_nr) {
+		ce = istate->cache[pos];
+		if (ce_namelen(ce) == fullname.len &&
+		    !memcmp(ce->name, fullname.buf, fullname.len))
+			die("Path '%s' is in the index, but not '%s'.\n"
+			    "Did you mean ':%d:%s' aka ':%d:./%s'?",
+			    fullname.buf, filename,
+			    ce_stage(ce), fullname.buf,
+			    ce_stage(ce), filename);
+	}
+
+	if (repo_file_exists(r, filename))
+		die("Path '%s' exists on disk, but not in the index.", filename);
+	if (is_missing_file_error(errno))
+		die("Path '%s' does not exist (neither on disk nor in the index).",
+		    filename);
+
+	strbuf_release(&fullname);
+}
+
+
+static char *resolve_relative_path(struct repository *r, const char *rel)
+{
+	if (!starts_with(rel, "./") && !starts_with(rel, "../"))
+		return NULL;
+
+	if (r != the_repository || !is_inside_work_tree())
+		die("relative path syntax can't be used outside working tree.");
+
+	/* die() inside prefix_path() if resolved path is outside worktree */
+	return prefix_path(startup_info->prefix,
+			   startup_info->prefix ? strlen(startup_info->prefix) : 0,
+			   rel);
+}
+
+static enum get_oid_result get_oid_with_context_1(struct repository *repo,
+				  const char *name,
+				  unsigned flags,
+				  const char *prefix,
+				  struct object_id *oid,
+				  struct object_context *oc)
+{
+	int ret, bracket_depth;
+	int namelen = strlen(name);
+	const char *cp;
+	int only_to_die = flags & GET_OID_ONLY_TO_DIE;
+
+	if (only_to_die)
+		flags |= GET_OID_QUIETLY;
+
+	memset(oc, 0, sizeof(*oc));
+	oc->mode = S_IFINVALID;
+	strbuf_init(&oc->symlink_path, 0);
+	ret = get_oid_1(repo, name, namelen, oid, flags);
+	if (!ret)
+		return ret;
+	/*
+	 * sha1:path --> object name of path in ent sha1
+	 * :path -> object name of absolute path in index
+	 * :./path -> object name of path relative to cwd in index
+	 * :[0-3]:path -> object name of path in index at stage
+	 * :/foo -> recent commit matching foo
+	 */
+	if (name[0] == ':') {
+		int stage = 0;
+		const struct cache_entry *ce;
+		char *new_path = NULL;
+		int pos;
+		if (!only_to_die && namelen > 2 && name[1] == '/') {
+			struct handle_one_ref_cb cb;
+			struct commit_list *list = NULL;
+
+			cb.repo = repo;
+			cb.list = &list;
+			refs_for_each_ref(repo->refs, handle_one_ref, &cb);
+			refs_head_ref(repo->refs, handle_one_ref, &cb);
+			commit_list_sort_by_date(&list);
+			return get_oid_oneline(repo, name + 2, oid, list);
+		}
+		if (namelen < 3 ||
+		    name[2] != ':' ||
+		    name[1] < '0' || '3' < name[1])
+			cp = name + 1;
+		else {
+			stage = name[1] - '0';
+			cp = name + 3;
+		}
+		new_path = resolve_relative_path(repo, cp);
+		if (!new_path) {
+			namelen = namelen - (cp - name);
+		} else {
+			cp = new_path;
+			namelen = strlen(cp);
+		}
+
+		if (flags & GET_OID_RECORD_PATH)
+			oc->path = xstrdup(cp);
+
+		if (!repo->index || !repo->index->cache)
+			repo_read_index(repo);
+		pos = index_name_pos(repo->index, cp, namelen);
+		if (pos < 0)
+			pos = -pos - 1;
+		while (pos < repo->index->cache_nr) {
+			ce = repo->index->cache[pos];
+			if (ce_namelen(ce) != namelen ||
+			    memcmp(ce->name, cp, namelen))
+				break;
+			if (ce_stage(ce) == stage) {
+				oidcpy(oid, &ce->oid);
+				oc->mode = ce->ce_mode;
+				free(new_path);
+				return 0;
+			}
+			pos++;
+		}
+		if (only_to_die && name[1] && name[1] != '/')
+			diagnose_invalid_index_path(repo, stage, prefix, cp);
+		free(new_path);
+		return -1;
+	}
+	for (cp = name, bracket_depth = 0; *cp; cp++) {
+		if (*cp == '{')
+			bracket_depth++;
+		else if (bracket_depth && *cp == '}')
+			bracket_depth--;
+		else if (!bracket_depth && *cp == ':')
+			break;
+	}
+	if (*cp == ':') {
+		struct object_id tree_oid;
+		int len = cp - name;
+		unsigned sub_flags = flags;
+
+		sub_flags &= ~GET_OID_DISAMBIGUATORS;
+		sub_flags |= GET_OID_TREEISH;
+
+		if (!get_oid_1(repo, name, len, &tree_oid, sub_flags)) {
+			const char *filename = cp+1;
+			char *new_filename = NULL;
+
+			new_filename = resolve_relative_path(repo, filename);
+			if (new_filename)
+				filename = new_filename;
+			if (flags & GET_OID_FOLLOW_SYMLINKS) {
+				ret = get_tree_entry_follow_symlinks(repo, &tree_oid,
+					filename, oid, &oc->symlink_path,
+					&oc->mode);
+			} else {
+				ret = get_tree_entry(repo, &tree_oid, filename, oid,
+						     &oc->mode);
+				if (ret && only_to_die) {
+					diagnose_invalid_oid_path(repo, prefix,
+								   filename,
+								   &tree_oid,
+								   name, len);
+				}
+			}
+			if (flags & GET_OID_RECORD_PATH)
+				oc->path = xstrdup(filename);
+
+			free(new_filename);
+			return ret;
+		} else {
+			if (only_to_die)
+				die("Invalid object name '%.*s'.", len, name);
+		}
+	}
+	return ret;
+}
+
+/*
+ * Call this function when you know "name" given by the end user must
+ * name an object but it doesn't; the function _may_ die with a better
+ * diagnostic message than "no such object 'name'", e.g. "Path 'doc' does not
+ * exist in 'HEAD'" when given "HEAD:doc", or it may return in which case
+ * you have a chance to diagnose the error further.
+ */
+void maybe_die_on_misspelt_object_name(struct repository *r,
+				       const char *name,
+				       const char *prefix)
+{
+	struct object_context oc;
+	struct object_id oid;
+	get_oid_with_context_1(r, name, GET_OID_ONLY_TO_DIE,
+			       prefix, &oid, &oc);
+}
+
+enum get_oid_result get_oid_with_context(struct repository *repo,
+					 const char *str,
+					 unsigned flags,
+					 struct object_id *oid,
+					 struct object_context *oc)
+{
+	if (flags & GET_OID_FOLLOW_SYMLINKS && flags & GET_OID_ONLY_TO_DIE)
+		BUG("incompatible flags for get_sha1_with_context");
+	return get_oid_with_context_1(repo, str, flags, NULL, oid, oc);
+}