sha1_name.c - jrn/git - Git at Google

 #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);
 }
	#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);
	}