[thirdparty/git.git] / sha1_name.c

#include "cache.h"
#include "tag.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"

static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
{
	struct alternate_object_database *alt;
	char hex[40];
	int found = 0;
	static struct alternate_object_database *fakeent;

	if (!fakeent) {
		const char *objdir = get_object_directory();
		int objdir_len = strlen(objdir);
		int entlen = objdir_len + 43;
		fakeent = xmalloc(sizeof(*fakeent) + entlen);
		memcpy(fakeent->base, objdir, objdir_len);
		fakeent->name = fakeent->base + objdir_len + 1;
		fakeent->name[-1] = '/';
	}
	fakeent->next = alt_odb_list;

	sprintf(hex, "%.2s", name);
	for (alt = fakeent; alt && found < 2; alt = alt->next) {
		struct dirent *de;
		DIR *dir;
		sprintf(alt->name, "%.2s/", name);
		dir = opendir(alt->base);
		if (!dir)
			continue;
		while ((de = readdir(dir)) != NULL) {
			if (strlen(de->d_name) != 38)
				continue;
			if (memcmp(de->d_name, name + 2, len - 2))
				continue;
			if (!found) {
				memcpy(hex + 2, de->d_name, 38);
				found++;
			}
			else if (memcmp(hex + 2, de->d_name, 38)) {
				found = 2;
				break;
			}
		}
		closedir(dir);
	}
	if (found == 1)
		return get_sha1_hex(hex, sha1) == 0;
	return found;
}

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 int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
{
	struct packed_git *p;
	unsigned char found_sha1[20];
	int found = 0;

	prepare_packed_git();
	for (p = packed_git; p && found < 2; p = p->next) {
		unsigned num = num_packed_objects(p);
		unsigned first = 0, last = num;
		while (first < last) {
			unsigned mid = (first + last) / 2;
			unsigned char now[20];
			int cmp;

			nth_packed_object_sha1(p, mid, now);
			cmp = memcmp(match, now, 20);
			if (!cmp) {
				first = mid;
				break;
			}
			if (cmp > 0) {
				first = mid+1;
				continue;
			}
			last = mid;
		}
		if (first < num) {
			unsigned char now[20], next[20];
			nth_packed_object_sha1(p, first, now);
			if (match_sha(len, match, now)) {
				if (nth_packed_object_sha1(p, first+1, next) ||
				    !match_sha(len, match, next)) {
					/* unique within this pack */
					if (!found) {
						memcpy(found_sha1, now, 20);
						found++;
					}
					else if (memcmp(found_sha1, now, 20)) {
						found = 2;
						break;
					}
				}
				else {
					/* not even unique within this pack */
					found = 2;
					break;
				}
			}
		}
	}
	if (found == 1)
		memcpy(sha1, found_sha1, 20);
	return found;
}

#define SHORT_NAME_NOT_FOUND (-1)
#define SHORT_NAME_AMBIGUOUS (-2)

static int find_unique_short_object(int len, char *canonical,
				    unsigned char *res, unsigned char *sha1)
{
	int has_unpacked, has_packed;
	unsigned char unpacked_sha1[20], packed_sha1[20];

	has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
	has_packed = find_short_packed_object(len, res, packed_sha1);
	if (!has_unpacked && !has_packed)
		return SHORT_NAME_NOT_FOUND;
	if (1 < has_unpacked || 1 < has_packed)
		return SHORT_NAME_AMBIGUOUS;
	if (has_unpacked != has_packed) {
		memcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1), 20);
		return 0;
	}
	/* Both have unique ones -- do they match? */
	if (memcmp(packed_sha1, unpacked_sha1, 20))
		return SHORT_NAME_AMBIGUOUS;
	memcpy(sha1, packed_sha1, 20);
	return 0;
}

static int get_short_sha1(const char *name, int len, unsigned char *sha1,
			  int quietly)
{
	int i, status;
	char canonical[40];
	unsigned char res[20];

	if (len < MINIMUM_ABBREV)
		return -1;
	memset(res, 0, 20);
	memset(canonical, 'x', 40);
	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;
		canonical[i] = c;
		if (!(i & 1))
			val <<= 4;
		res[i >> 1] |= val;
	}

	status = find_unique_short_object(i, canonical, res, sha1);
	if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
		return error("short SHA1 %.*s is ambiguous.", len, canonical);
	return status;
}

const char *find_unique_abbrev(const unsigned char *sha1, int len)
{
	int status, is_null;
	static char hex[41];

	is_null = !memcmp(sha1, null_sha1, 20);
	memcpy(hex, sha1_to_hex(sha1), 40);
	if (len == 40)
		return hex;
	while (len < 40) {
		unsigned char sha1_ret[20];
		status = get_short_sha1(hex, len, sha1_ret, 1);
		if (!status ||
		    (is_null && status != SHORT_NAME_AMBIGUOUS)) {
			hex[len] = 0;
			return hex;
		}
		if (status != SHORT_NAME_AMBIGUOUS)
			return NULL;
		len++;
	}
	return NULL;
}

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 int get_sha1_basic(const char *str, int len, unsigned char *sha1)
{
	static const char *fmt[] = {
		"%.*s",
		"refs/%.*s",
		"refs/tags/%.*s",
		"refs/heads/%.*s",
		"refs/remotes/%.*s",
		"refs/remotes/%.*s/HEAD",
		NULL
	};
	const char **p;
	const char *warning = "warning: refname '%.*s' is ambiguous.\n";
	char *pathname;
	int already_found = 0;
	unsigned char *this_result;
	unsigned char sha1_from_ref[20];

	if (len == 40 && !get_sha1_hex(str, sha1))
		return 0;

	/* Accept only unambiguous ref paths. */
	if (ambiguous_path(str, len))
		return -1;

	for (p = fmt; *p; p++) {
		this_result = already_found ? sha1_from_ref : sha1;
		pathname = git_path(*p, len, str);
		if (!read_ref(pathname, this_result)) {
			if (warn_ambiguous_refs) {
				if (already_found)
					fprintf(stderr, warning, len, str);
				already_found++;
			}
			else
				return 0;
		}
	}
	if (already_found)
		return 0;
	return -1;
}

static int get_sha1_1(const char *name, int len, unsigned char *sha1);

static int get_parent(const char *name, int len,
		      unsigned char *result, int idx)
{
	unsigned char sha1[20];
	int ret = get_sha1_1(name, len, sha1);
	struct commit *commit;
	struct commit_list *p;

	if (ret)
		return ret;
	commit = lookup_commit_reference(sha1);
	if (!commit)
		return -1;
	if (parse_commit(commit))
		return -1;
	if (!idx) {
		memcpy(result, commit->object.sha1, 20);
		return 0;
	}
	p = commit->parents;
	while (p) {
		if (!--idx) {
			memcpy(result, p->item->object.sha1, 20);
			return 0;
		}
		p = p->next;
	}
	return -1;
}

static int get_nth_ancestor(const char *name, int len,
			    unsigned char *result, int generation)
{
	unsigned char sha1[20];
	int ret = get_sha1_1(name, len, sha1);
	if (ret)
		return ret;

	while (generation--) {
		struct commit *commit = lookup_commit_reference(sha1);

		if (!commit || parse_commit(commit) || !commit->parents)
			return -1;
		memcpy(sha1, commit->parents->item->object.sha1, 20);
	}
	memcpy(result, sha1, 20);
	return 0;
}

static int peel_onion(const char *name, int len, unsigned char *sha1)
{
	unsigned char outer[20];
	const char *sp;
	const char *type_string = NULL;
	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 (!strncmp(commit_type, sp, 6) && sp[6] == '}')
		type_string = commit_type;
	else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
		type_string = tree_type;
	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
		type_string = blob_type;
	else if (sp[0] == '}')
		type_string = NULL;
	else
		return -1;

	if (get_sha1_1(name, sp - name - 2, outer))
		return -1;

	o = parse_object(outer);
	if (!o)
		return -1;
	if (!type_string) {
		o = deref_tag(o, name, sp - name - 2);
		if (!o || (!o->parsed && !parse_object(o->sha1)))
			return -1;
		memcpy(sha1, o->sha1, 20);
	}
	else {
		/* At this point, the syntax look correct, so
		 * if we do not get the needed object, we should
		 * barf.
		 */

		while (1) {
			if (!o || (!o->parsed && !parse_object(o->sha1)))
				return -1;
			if (o->type == type_string) {
				memcpy(sha1, o->sha1, 20);
				return 0;
			}
			if (o->type == tag_type)
				o = ((struct tag*) o)->tagged;
			else if (o->type == commit_type)
				o = &(((struct commit *) o)->tree->object);
			else
				return error("%.*s: expected %s type, but the object dereferences to %s type",
					     len, name, type_string,
					     o->type);
			if (!o->parsed)
				parse_object(o->sha1);
		}
	}
	return 0;
}

static int get_sha1_1(const char *name, int len, unsigned char *sha1)
{
	int ret, has_suffix;
	const char *cp;

	/* "name~3" is "name^^^",
	 * "name~" and "name~0" are name -- not "name^0"!
	 * "name^" is not "name^0"; it 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 (has_suffix == '^') {
			if (!num && len1 == len - 1)
				num = 1;
			return get_parent(name, len1, sha1, num);
		}
		/* else if (has_suffix == '~') -- goes without saying */
		return get_nth_ancestor(name, len1, sha1, num);
	}

	ret = peel_onion(name, len, sha1);
	if (!ret)
		return 0;

	ret = get_sha1_basic(name, len, sha1);
	if (!ret)
		return 0;
	return get_short_sha1(name, len, sha1, 0);
}

/*
 * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 * notably "xyz^" for "parent of xyz"
 */
int get_sha1(const char *name, unsigned char *sha1)
{
	prepare_alt_odb();
	return get_sha1_1(name, strlen(name), sha1);
}
Commit	Line	Data
9938af6a	1	#include "cache.h"
5385f52d	2	#include "tag.h"
9938af6a	3	#include "commit.h"
5385f52d JH	4	#include "tree.h"
5385f52d JH	5	#include "blob.h"
9938af6a JH	6
	7	static int find_short_object_filename(int len, const char name, unsigned char sha1)
	8	{
99a19b43	9	struct alternate_object_database *alt;
9938af6a	10	char hex[40];
99a19b43 JH	11	int found = 0;
	12	static struct alternate_object_database *fakeent;
	13
	14	if (!fakeent) {
	15	const char *objdir = get_object_directory();
	16	int objdir_len = strlen(objdir);
	17	int entlen = objdir_len + 43;
	18	fakeent = xmalloc(sizeof(*fakeent) + entlen);
	19	memcpy(fakeent->base, objdir, objdir_len);
	20	fakeent->name = fakeent->base + objdir_len + 1;
	21	fakeent->name[-1] = '/';
	22	}
	23	fakeent->next = alt_odb_list;
9938af6a	24
9938af6a	25	sprintf(hex, "%.2s", name);
99a19b43	26	for (alt = fakeent; alt && found < 2; alt = alt->next) {
9938af6a	27	struct dirent *de;
99a19b43 JH	28	DIR *dir;
	29	sprintf(alt->name, "%.2s/", name);
	30	dir = opendir(alt->base);
	31	if (!dir)
	32	continue;
9938af6a JH	33	while ((de = readdir(dir)) != NULL) {
	34	if (strlen(de->d_name) != 38)
	35	continue;
99a19b43	36	if (memcmp(de->d_name, name + 2, len - 2))
9938af6a	37	continue;
99a19b43 JH	38	if (!found) {
	39	memcpy(hex + 2, de->d_name, 38);
	40	found++;
	41	}
	42	else if (memcmp(hex + 2, de->d_name, 38)) {
	43	found = 2;
9938af6a	44	break;
99a19b43	45	}
9938af6a JH	46	}
	47	closedir(dir);
	48	}
	49	if (found == 1)
	50	return get_sha1_hex(hex, sha1) == 0;
99a19b43	51	return found;
9938af6a JH	52	}
	53
	54	static int match_sha(unsigned len, const unsigned char a, const unsigned char b)
	55	{
	56	do {
	57	if (a != b)
	58	return 0;
	59	a++;
	60	b++;
	61	len -= 2;
	62	} while (len > 1);
	63	if (len)
	64	if ((a ^ b) & 0xf0)
	65	return 0;
	66	return 1;
	67	}
	68
	69	static int find_short_packed_object(int len, const unsigned char match, unsigned char sha1)
	70	{
	71	struct packed_git *p;
99a19b43 JH	72	unsigned char found_sha1[20];
99a19b43 JH	73	int found = 0;
9938af6a JH	74
9938af6a JH	75	prepare_packed_git();
99a19b43	76	for (p = packed_git; p && found < 2; p = p->next) {
9938af6a JH	77	unsigned num = num_packed_objects(p);
	78	unsigned first = 0, last = num;
	79	while (first < last) {
	80	unsigned mid = (first + last) / 2;
	81	unsigned char now[20];
	82	int cmp;
	83
	84	nth_packed_object_sha1(p, mid, now);
	85	cmp = memcmp(match, now, 20);
	86	if (!cmp) {
	87	first = mid;
	88	break;
	89	}
	90	if (cmp > 0) {
	91	first = mid+1;
	92	continue;
	93	}
	94	last = mid;
	95	}
	96	if (first < num) {
0bc45890	97	unsigned char now[20], next[20];
9938af6a JH	98	nth_packed_object_sha1(p, first, now);
9938af6a JH	99	if (match_sha(len, match, now)) {
0bc45890 JH	100	if (nth_packed_object_sha1(p, first+1, next) \|\|
	101	!match_sha(len, match, next)) {
	102	/* unique within this pack */
	103	if (!found) {
	104	memcpy(found_sha1, now, 20);
	105	found++;
	106	}
	107	else if (memcmp(found_sha1, now, 20)) {
	108	found = 2;
	109	break;
	110	}
99a19b43	111	}
0bc45890 JH	112	else {
0bc45890 JH	113	/* not even unique within this pack */
99a19b43 JH	114	found = 2;
99a19b43 JH	115	break;
9938af6a JH	116	}
	117	}
	118	}
	119	}
99a19b43 JH	120	if (found == 1)
	121	memcpy(sha1, found_sha1, 20);
	122	return found;
	123	}
	124
013f276e JH	125	#define SHORT_NAME_NOT_FOUND (-1)
	126	#define SHORT_NAME_AMBIGUOUS (-2)
	127
99a19b43 JH	128	static int find_unique_short_object(int len, char *canonical,
	129	unsigned char res, unsigned char sha1)
	130	{
	131	int has_unpacked, has_packed;
	132	unsigned char unpacked_sha1[20], packed_sha1[20];
	133
	134	has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
	135	has_packed = find_short_packed_object(len, res, packed_sha1);
	136	if (!has_unpacked && !has_packed)
013f276e	137	return SHORT_NAME_NOT_FOUND;
99a19b43	138	if (1 < has_unpacked \|\| 1 < has_packed)
013f276e	139	return SHORT_NAME_AMBIGUOUS;
99a19b43 JH	140	if (has_unpacked != has_packed) {
	141	memcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1), 20);
	142	return 0;
	143	}
	144	/* Both have unique ones -- do they match? */
	145	if (memcmp(packed_sha1, unpacked_sha1, 20))
e974c9ab	146	return SHORT_NAME_AMBIGUOUS;
99a19b43	147	memcpy(sha1, packed_sha1, 20);
9938af6a JH	148	return 0;
	149	}
	150
013f276e JH	151	static int get_short_sha1(const char name, int len, unsigned char sha1,
013f276e JH	152	int quietly)
9938af6a	153	{
013f276e	154	int i, status;
9938af6a JH	155	char canonical[40];
	156	unsigned char res[20];
	157
46a6c262	158	if (len < MINIMUM_ABBREV)
af61c6e0	159	return -1;
9938af6a JH	160	memset(res, 0, 20);
9938af6a JH	161	memset(canonical, 'x', 40);
af61c6e0	162	for (i = 0; i < len ;i++) {
9938af6a JH	163	unsigned char c = name[i];
9938af6a JH	164	unsigned char val;
9938af6a JH	165	if (c >= '0' && c <= '9')
	166	val = c - '0';
	167	else if (c >= 'a' && c <= 'f')
	168	val = c - 'a' + 10;
	169	else if (c >= 'A' && c <='F') {
	170	val = c - 'A' + 10;
	171	c -= 'A' - 'a';
	172	}
	173	else
	174	return -1;
	175	canonical[i] = c;
	176	if (!(i & 1))
	177	val <<= 4;
	178	res[i >> 1] \|= val;
	179	}
99a19b43	180
013f276e JH	181	status = find_unique_short_object(i, canonical, res, sha1);
	182	if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
	183	return error("short SHA1 %.*s is ambiguous.", len, canonical);
	184	return status;
	185	}
	186
	187	const char find_unique_abbrev(const unsigned char sha1, int len)
	188	{
297a1aad	189	int status, is_null;
013f276e	190	static char hex[41];
47dd0d59	191
297a1aad	192	is_null = !memcmp(sha1, null_sha1, 20);
013f276e	193	memcpy(hex, sha1_to_hex(sha1), 40);
47dd0d59 JH	194	if (len == 40)
47dd0d59 JH	195	return hex;
013f276e JH	196	while (len < 40) {
	197	unsigned char sha1_ret[20];
	198	status = get_short_sha1(hex, len, sha1_ret, 1);
297a1aad JH	199	if (!status \|\|
297a1aad JH	200	(is_null && status != SHORT_NAME_AMBIGUOUS)) {
013f276e JH	201	hex[len] = 0;
	202	return hex;
	203	}
	204	if (status != SHORT_NAME_AMBIGUOUS)
	205	return NULL;
	206	len++;
	207	}
	208	return NULL;
9938af6a JH	209	}
9938af6a JH	210
6677c466	211	static int ambiguous_path(const char *path, int len)
af13cdf2 LT	212	{
af13cdf2 LT	213	int slash = 1;
6677c466	214	int cnt;
af13cdf2	215
6677c466	216	for (cnt = 0; cnt < len; cnt++) {
af13cdf2 LT	217	switch (*path++) {
	218	case '\0':
	219	break;
	220	case '/':
	221	if (slash)
	222	break;
	223	slash = 1;
	224	continue;
	225	case '.':
	226	continue;
	227	default:
	228	slash = 0;
	229	continue;
	230	}
c054d64e	231	break;
af13cdf2	232	}
6677c466	233	return slash;
af13cdf2 LT	234	}
af13cdf2 LT	235
9938af6a JH	236	static int get_sha1_basic(const char str, int len, unsigned char sha1)
9938af6a JH	237	{
c51d1369	238	static const char *fmt[] = {
84a9b58c	239	"%.*s",
c51d1369 JH	240	"refs/%.*s",
	241	"refs/tags/%.*s",
	242	"refs/heads/%.*s",
	243	"refs/remotes/%.*s",
	244	"refs/remotes/%.*s/HEAD",
9938af6a JH	245	NULL
	246	};
	247	const char **p;
2f8acdb3 JH	248	const char warning = "warning: refname '%.s' is ambiguous.\n";
	249	char *pathname;
	250	int already_found = 0;
c51d1369 JH	251	unsigned char *this_result;
c51d1369 JH	252	unsigned char sha1_from_ref[20];
9938af6a	253
3c3852e3	254	if (len == 40 && !get_sha1_hex(str, sha1))
9938af6a JH	255	return 0;
9938af6a JH	256
af13cdf2	257	/* Accept only unambiguous ref paths. */
6677c466	258	if (ambiguous_path(str, len))
af13cdf2 LT	259	return -1;
af13cdf2 LT	260
c51d1369 JH	261	for (p = fmt; *p; p++) {
	262	this_result = already_found ? sha1_from_ref : sha1;
	263	pathname = git_path(*p, len, str);
2f8acdb3 JH	264	if (!read_ref(pathname, this_result)) {
2f8acdb3 JH	265	if (warn_ambiguous_refs) {
84a9b58c	266	if (already_found)
2f8acdb3 JH	267	fprintf(stderr, warning, len, str);
	268	already_found++;
	269	}
	270	else
	271	return 0;
	272	}
6677c466	273	}
2f8acdb3 JH	274	if (already_found)
2f8acdb3 JH	275	return 0;
011fbc7f	276	return -1;
9938af6a JH	277	}
	278
	279	static int get_sha1_1(const char name, int len, unsigned char sha1);
	280
	281	static int get_parent(const char *name, int len,
	282	unsigned char *result, int idx)
	283	{
	284	unsigned char sha1[20];
	285	int ret = get_sha1_1(name, len, sha1);
	286	struct commit *commit;
	287	struct commit_list *p;
	288
	289	if (ret)
	290	return ret;
	291	commit = lookup_commit_reference(sha1);
	292	if (!commit)
	293	return -1;
	294	if (parse_commit(commit))
	295	return -1;
	296	if (!idx) {
	297	memcpy(result, commit->object.sha1, 20);
	298	return 0;
	299	}
	300	p = commit->parents;
	301	while (p) {
	302	if (!--idx) {
	303	memcpy(result, p->item->object.sha1, 20);
	304	return 0;
	305	}
	306	p = p->next;
	307	}
	308	return -1;
	309	}
	310
4f7599ac JH	311	static int get_nth_ancestor(const char *name, int len,
	312	unsigned char *result, int generation)
	313	{
	314	unsigned char sha1[20];
	315	int ret = get_sha1_1(name, len, sha1);
	316	if (ret)
	317	return ret;
	318
	319	while (generation--) {
	320	struct commit *commit = lookup_commit_reference(sha1);
	321
	322	if (!commit \|\| parse_commit(commit) \|\| !commit->parents)
	323	return -1;
	324	memcpy(sha1, commit->parents->item->object.sha1, 20);
	325	}
	326	memcpy(result, sha1, 20);
	327	return 0;
	328	}
	329
5385f52d JH	330	static int peel_onion(const char name, int len, unsigned char sha1)
	331	{
	332	unsigned char outer[20];
	333	const char *sp;
	334	const char *type_string = NULL;
	335	struct object *o;
	336
	337	/*
	338	* "ref^{type}" dereferences ref repeatedly until you cannot
	339	* dereference anymore, or you get an object of given type,
	340	* whichever comes first. "ref^{}" means just dereference
	341	* tags until you get a non-tag. "ref^0" is a shorthand for
	342	* "ref^{commit}". "commit^{tree}" could be used to find the
	343	* top-level tree of the given commit.
	344	*/
	345	if (len < 4 \|\| name[len-1] != '}')
	346	return -1;
	347
	348	for (sp = name + len - 1; name <= sp; sp--) {
	349	int ch = *sp;
	350	if (ch == '{' && name < sp && sp[-1] == '^')
	351	break;
	352	}
	353	if (sp <= name)
	354	return -1;
	355
	356	sp++; /* beginning of type name, or closing brace for empty */
	357	if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
	358	type_string = commit_type;
	359	else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
	360	type_string = tree_type;
	361	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
	362	type_string = blob_type;
	363	else if (sp[0] == '}')
	364	type_string = NULL;
	365	else
	366	return -1;
	367
	368	if (get_sha1_1(name, sp - name - 2, outer))
	369	return -1;
	370
	371	o = parse_object(outer);
	372	if (!o)
	373	return -1;
	374	if (!type_string) {
9534f40b	375	o = deref_tag(o, name, sp - name - 2);
6e1c6c10 JH	376	if (!o \|\| (!o->parsed && !parse_object(o->sha1)))
6e1c6c10 JH	377	return -1;
5385f52d JH	378	memcpy(sha1, o->sha1, 20);
	379	}
	380	else {
	381	/* At this point, the syntax look correct, so
	382	* if we do not get the needed object, we should
	383	* barf.
	384	*/
	385
	386	while (1) {
6e1c6c10	387	if (!o \|\| (!o->parsed && !parse_object(o->sha1)))
5385f52d JH	388	return -1;
	389	if (o->type == type_string) {
	390	memcpy(sha1, o->sha1, 20);
	391	return 0;
	392	}
	393	if (o->type == tag_type)
	394	o = ((struct tag*) o)->tagged;
	395	else if (o->type == commit_type)
	396	o = &(((struct commit *) o)->tree->object);
	397	else
	398	return error("%.*s: expected %s type, but the object dereferences to %s type",
	399	len, name, type_string,
	400	o->type);
	401	if (!o->parsed)
	402	parse_object(o->sha1);
	403	}
	404	}
	405	return 0;
	406	}
	407
9938af6a JH	408	static int get_sha1_1(const char name, int len, unsigned char sha1)
9938af6a JH	409	{
0601dbe1	410	int ret, has_suffix;
4f7599ac	411	const char *cp;
9938af6a	412
4f7599ac	413	/* "name~3" is "name^^^",
4f7599ac	414	* "name~" and "name~0" are name -- not "name^0"!
0601dbe1	415	* "name^" is not "name^0"; it is "name^1".
4f7599ac	416	*/
0601dbe1	417	has_suffix = 0;
4f7599ac JH	418	for (cp = name + len - 1; name <= cp; cp--) {
	419	int ch = *cp;
	420	if ('0' <= ch && ch <= '9')
	421	continue;
0601dbe1 JH	422	if (ch == '~' \|\| ch == '^')
0601dbe1 JH	423	has_suffix = ch;
4f7599ac JH	424	break;
4f7599ac JH	425	}
0601dbe1 JH	426
	427	if (has_suffix) {
	428	int num = 0;
4f7599ac JH	429	int len1 = cp - name;
	430	cp++;
	431	while (cp < name + len)
0601dbe1 JH	432	num = num * 10 + *cp++ - '0';
	433	if (has_suffix == '^') {
	434	if (!num && len1 == len - 1)
	435	num = 1;
	436	return get_parent(name, len1, sha1, num);
	437	}
	438	/* else if (has_suffix == '~') -- goes without saying */
	439	return get_nth_ancestor(name, len1, sha1, num);
4f7599ac JH	440	}
4f7599ac JH	441
5385f52d JH	442	ret = peel_onion(name, len, sha1);
	443	if (!ret)
	444	return 0;
	445
9938af6a JH	446	ret = get_sha1_basic(name, len, sha1);
	447	if (!ret)
	448	return 0;
013f276e	449	return get_short_sha1(name, len, sha1, 0);
9938af6a JH	450	}
	451
	452	/*
	453	* This is like "get_sha1_basic()", except it allows "sha1 expressions",
	454	* notably "xyz^" for "parent of xyz"
	455	*/
	456	int get_sha1(const char name, unsigned char sha1)
	457	{
99a19b43	458	prepare_alt_odb();
9938af6a JH	459	return get_sha1_1(name, strlen(name), sha1);
9938af6a JH	460	}