[thirdparty/git.git] / match-trees.c

#include "cache.h"
#include "tree.h"
#include "tree-walk.h"

static int score_missing(unsigned mode, const char *path)
{
	int score;

	if (S_ISDIR(mode))
		score = -1000;
	else if (S_ISLNK(mode))
		score = -500;
	else
		score = -50;
	return score;
}

static int score_differs(unsigned mode1, unsigned mode2, const char *path)
{
	int score;

	if (S_ISDIR(mode1) != S_ISDIR(mode2))
		score = -100;
	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
		score = -50;
	else
		score = -5;
	return score;
}

static int score_matches(unsigned mode1, unsigned mode2, const char *path)
{
	int score;

	/* Heh, we found SHA-1 collisions between different kind of objects */
	if (S_ISDIR(mode1) != S_ISDIR(mode2))
		score = -100;
	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
		score = -50;

	else if (S_ISDIR(mode1))
		score = 1000;
	else if (S_ISLNK(mode1))
		score = 500;
	else
		score = 250;
	return score;
}

static int base_name_entries_compare(const struct name_entry *a,
				     const struct name_entry *b)
{
	return base_name_compare(a->path, tree_entry_len(a), a->mode,
				 b->path, tree_entry_len(b), b->mode);
}

/*
 * Inspect two trees, and give a score that tells how similar they are.
 */
static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
{
	struct tree_desc one;
	struct tree_desc two;
	void *one_buf, *two_buf;
	int score = 0;
	enum object_type type;
	unsigned long size;

	one_buf = read_sha1_file(hash1, &type, &size);
	if (!one_buf)
		die("unable to read tree (%s)", sha1_to_hex(hash1));
	if (type != OBJ_TREE)
		die("%s is not a tree", sha1_to_hex(hash1));
	init_tree_desc(&one, one_buf, size);
	two_buf = read_sha1_file(hash2, &type, &size);
	if (!two_buf)
		die("unable to read tree (%s)", sha1_to_hex(hash2));
	if (type != OBJ_TREE)
		die("%s is not a tree", sha1_to_hex(hash2));
	init_tree_desc(&two, two_buf, size);
	for (;;) {
		struct name_entry e1, e2;
		int got_entry_from_one = tree_entry(&one, &e1);
		int got_entry_from_two = tree_entry(&two, &e2);
		int cmp;

		if (got_entry_from_one && got_entry_from_two)
			cmp = base_name_entries_compare(&e1, &e2);
		else if (got_entry_from_one)
			/* two lacks this entry */
			cmp = -1;
		else if (got_entry_from_two)
			/* two has more entries */
			cmp = 1;
		else
			break;

		if (cmp < 0)
			/* path1 does not appear in two */
			score += score_missing(e1.mode, e1.path);
		else if (cmp > 0)
			/* path2 does not appear in one */
			score += score_missing(e2.mode, e2.path);
		else if (hashcmp(e1.sha1, e2.sha1))
			/* they are different */
			score += score_differs(e1.mode, e2.mode, e1.path);
		else
			/* same subtree or blob */
			score += score_matches(e1.mode, e2.mode, e1.path);
	}
	free(one_buf);
	free(two_buf);
	return score;
}

/*
 * Match one itself and its subtrees with two and pick the best match.
 */
static void match_trees(const unsigned char *hash1,
			const unsigned char *hash2,
			int *best_score,
			char **best_match,
			const char *base,
			int recurse_limit)
{
	struct tree_desc one;
	void *one_buf;
	enum object_type type;
	unsigned long size;

	one_buf = read_sha1_file(hash1, &type, &size);
	if (!one_buf)
		die("unable to read tree (%s)", sha1_to_hex(hash1));
	if (type != OBJ_TREE)
		die("%s is not a tree", sha1_to_hex(hash1));
	init_tree_desc(&one, one_buf, size);

	while (one.size) {
		const char *path;
		const unsigned char *elem;
		unsigned mode;
		int score;

		elem = tree_entry_extract(&one, &path, &mode);
		if (!S_ISDIR(mode))
			goto next;
		score = score_trees(elem, hash2);
		if (*best_score < score) {
			char *newpath;
			newpath = xmalloc(strlen(base) + strlen(path) + 1);
			sprintf(newpath, "%s%s", base, path);
			free(*best_match);
			*best_match = newpath;
			*best_score = score;
		}
		if (recurse_limit) {
			char *newbase;
			newbase = xmalloc(strlen(base) + strlen(path) + 2);
			sprintf(newbase, "%s%s/", base, path);
			match_trees(elem, hash2, best_score, best_match,
				    newbase, recurse_limit - 1);
			free(newbase);
		}

	next:
		update_tree_entry(&one);
	}
	free(one_buf);
}

/*
 * A tree "hash1" has a subdirectory at "prefix".  Come up with a
 * tree object by replacing it with another tree "hash2".
 */
static int splice_tree(const unsigned char *hash1,
		       const char *prefix,
		       const unsigned char *hash2,
		       unsigned char *result)
{
	char *subpath;
	int toplen;
	char *buf;
	unsigned long sz;
	struct tree_desc desc;
	unsigned char *rewrite_here;
	const unsigned char *rewrite_with;
	unsigned char subtree[20];
	enum object_type type;
	int status;

	subpath = strchr(prefix, '/');
	if (!subpath)
		toplen = strlen(prefix);
	else {
		toplen = subpath - prefix;
		subpath++;
	}

	buf = read_sha1_file(hash1, &type, &sz);
	if (!buf)
		die("cannot read tree %s", sha1_to_hex(hash1));
	init_tree_desc(&desc, buf, sz);

	rewrite_here = NULL;
	while (desc.size) {
		const char *name;
		unsigned mode;
		const unsigned char *sha1;

		sha1 = tree_entry_extract(&desc, &name, &mode);
		if (strlen(name) == toplen &&
		    !memcmp(name, prefix, toplen)) {
			if (!S_ISDIR(mode))
				die("entry %s in tree %s is not a tree",
				    name, sha1_to_hex(hash1));
			rewrite_here = (unsigned char *) sha1;
			break;
		}
		update_tree_entry(&desc);
	}
	if (!rewrite_here)
		die("entry %.*s not found in tree %s",
		    toplen, prefix, sha1_to_hex(hash1));
	if (subpath) {
		status = splice_tree(rewrite_here, subpath, hash2, subtree);
		if (status)
			return status;
		rewrite_with = subtree;
	}
	else
		rewrite_with = hash2;
	hashcpy(rewrite_here, rewrite_with);
	status = write_sha1_file(buf, sz, tree_type, result);
	free(buf);
	return status;
}

/*
 * We are trying to come up with a merge between one and two that
 * results in a tree shape similar to one.  The tree two might
 * correspond to a subtree of one, in which case it needs to be
 * shifted down by prefixing otherwise empty directories.  On the
 * other hand, it could cover tree one and we might need to pick a
 * subtree of it.
 */
void shift_tree(const unsigned char *hash1,
		const unsigned char *hash2,
		unsigned char *shifted,
		int depth_limit)
{
	char *add_prefix;
	char *del_prefix;
	int add_score, del_score;

	/*
	 * NEEDSWORK: this limits the recursion depth to hardcoded
	 * value '2' to avoid excessive overhead.
	 */
	if (!depth_limit)
		depth_limit = 2;

	add_score = del_score = score_trees(hash1, hash2);
	add_prefix = xcalloc(1, 1);
	del_prefix = xcalloc(1, 1);

	/*
	 * See if one's subtree resembles two; if so we need to prefix
	 * two with a few fake trees to match the prefix.
	 */
	match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);

	/*
	 * See if two's subtree resembles one; if so we need to
	 * pick only subtree of two.
	 */
	match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);

	/* Assume we do not have to do any shifting */
	hashcpy(shifted, hash2);

	if (add_score < del_score) {
		/* We need to pick a subtree of two */
		unsigned mode;

		if (!*del_prefix)
			return;

		if (get_tree_entry(hash2, del_prefix, shifted, &mode))
			die("cannot find path %s in tree %s",
			    del_prefix, sha1_to_hex(hash2));
		return;
	}

	if (!*add_prefix)
		return;

	splice_tree(hash1, add_prefix, hash2, shifted);
}

/*
 * The user says the trees will be shifted by this much.
 * Unfortunately we cannot fundamentally tell which one to
 * be prefixed, as recursive merge can work in either direction.
 */
void shift_tree_by(const unsigned char *hash1,
		   const unsigned char *hash2,
		   unsigned char *shifted,
		   const char *shift_prefix)
{
	unsigned char sub1[20], sub2[20];
	unsigned mode1, mode2;
	unsigned candidate = 0;

	/* Can hash2 be a tree at shift_prefix in tree hash1? */
	if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
	    S_ISDIR(mode1))
		candidate |= 1;

	/* Can hash1 be a tree at shift_prefix in tree hash2? */
	if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
	    S_ISDIR(mode2))
		candidate |= 2;

	if (candidate == 3) {
		/* Both are plausible -- we need to evaluate the score */
		int best_score = score_trees(hash1, hash2);
		int score;

		candidate = 0;
		score = score_trees(sub1, hash2);
		if (score > best_score) {
			candidate = 1;
			best_score = score;
		}
		score = score_trees(sub2, hash1);
		if (score > best_score)
			candidate = 2;
	}

	if (!candidate) {
		/* Neither is plausible -- do not shift */
		hashcpy(shifted, hash2);
		return;
	}

	if (candidate == 1)
		/*
		 * shift tree2 down by adding shift_prefix above it
		 * to match tree1.
		 */
		splice_tree(hash1, shift_prefix, hash2, shifted);
	else
		/*
		 * shift tree2 up by removing shift_prefix from it
		 * to match tree1.
		 */
		hashcpy(shifted, sub2);
}
Commit	Line	Data
68faf689 JH	1	#include "cache.h"
	2	#include "tree.h"
	3	#include "tree-walk.h"
	4
	5	static int score_missing(unsigned mode, const char *path)
	6	{
	7	int score;
	8
	9	if (S_ISDIR(mode))
	10	score = -1000;
	11	else if (S_ISLNK(mode))
	12	score = -500;
	13	else
	14	score = -50;
	15	return score;
	16	}
	17
	18	static int score_differs(unsigned mode1, unsigned mode2, const char *path)
	19	{
	20	int score;
	21
	22	if (S_ISDIR(mode1) != S_ISDIR(mode2))
	23	score = -100;
	24	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
	25	score = -50;
	26	else
	27	score = -5;
	28	return score;
	29	}
	30
	31	static int score_matches(unsigned mode1, unsigned mode2, const char *path)
	32	{
	33	int score;
	34
	35	/* Heh, we found SHA-1 collisions between different kind of objects */
	36	if (S_ISDIR(mode1) != S_ISDIR(mode2))
	37	score = -100;
	38	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
	39	score = -50;
	40
	41	else if (S_ISDIR(mode1))
	42	score = 1000;
	43	else if (S_ISLNK(mode1))
	44	score = 500;
	45	else
	46	score = 250;
	47	return score;
	48	}
	49
d8febde3 RS	50	static int base_name_entries_compare(const struct name_entry *a,
	51	const struct name_entry *b)
	52	{
	53	return base_name_compare(a->path, tree_entry_len(a), a->mode,
	54	b->path, tree_entry_len(b), b->mode);
	55	}
	56
68faf689 JH	57	/*
	58	* Inspect two trees, and give a score that tells how similar they are.
	59	*/
	60	static int score_trees(const unsigned char hash1, const unsigned char hash2)
	61	{
	62	struct tree_desc one;
	63	struct tree_desc two;
	64	void one_buf, two_buf;
	65	int score = 0;
	66	enum object_type type;
	67	unsigned long size;
	68
	69	one_buf = read_sha1_file(hash1, &type, &size);
	70	if (!one_buf)
	71	die("unable to read tree (%s)", sha1_to_hex(hash1));
	72	if (type != OBJ_TREE)
	73	die("%s is not a tree", sha1_to_hex(hash1));
	74	init_tree_desc(&one, one_buf, size);
	75	two_buf = read_sha1_file(hash2, &type, &size);
	76	if (!two_buf)
	77	die("unable to read tree (%s)", sha1_to_hex(hash2));
	78	if (type != OBJ_TREE)
	79	die("%s is not a tree", sha1_to_hex(hash2));
	80	init_tree_desc(&two, two_buf, size);
d8febde3 RS	81	for (;;) {
	82	struct name_entry e1, e2;
	83	int got_entry_from_one = tree_entry(&one, &e1);
	84	int got_entry_from_two = tree_entry(&two, &e2);
68faf689 JH	85	int cmp;
68faf689 JH	86
d8febde3 RS	87	if (got_entry_from_one && got_entry_from_two)
	88	cmp = base_name_entries_compare(&e1, &e2);
	89	else if (got_entry_from_one)
68faf689	90	/* two lacks this entry */
d8febde3 RS	91	cmp = -1;
	92	else if (got_entry_from_two)
	93	/* two has more entries */
	94	cmp = 1;
	95	else
	96	break;
	97
	98	if (cmp < 0)
68faf689	99	/* path1 does not appear in two */
d8febde3 RS	100	score += score_missing(e1.mode, e1.path);
d8febde3 RS	101	else if (cmp > 0)
68faf689	102	/* path2 does not appear in one */
d8febde3 RS	103	score += score_missing(e2.mode, e2.path);
d8febde3 RS	104	else if (hashcmp(e1.sha1, e2.sha1))
68faf689	105	/* they are different */
d8febde3	106	score += score_differs(e1.mode, e2.mode, e1.path);
68faf689 JH	107	else
68faf689 JH	108	/* same subtree or blob */
d8febde3	109	score += score_matches(e1.mode, e2.mode, e1.path);
68faf689 JH	110	}
	111	free(one_buf);
	112	free(two_buf);
	113	return score;
	114	}
	115
	116	/*
	117	* Match one itself and its subtrees with two and pick the best match.
	118	*/
	119	static void match_trees(const unsigned char *hash1,
	120	const unsigned char *hash2,
	121	int *best_score,
	122	char **best_match,
538dfe73	123	const char *base,
68faf689 JH	124	int recurse_limit)
	125	{
	126	struct tree_desc one;
	127	void *one_buf;
	128	enum object_type type;
	129	unsigned long size;
	130
	131	one_buf = read_sha1_file(hash1, &type, &size);
	132	if (!one_buf)
	133	die("unable to read tree (%s)", sha1_to_hex(hash1));
	134	if (type != OBJ_TREE)
	135	die("%s is not a tree", sha1_to_hex(hash1));
	136	init_tree_desc(&one, one_buf, size);
	137
	138	while (one.size) {
	139	const char *path;
	140	const unsigned char *elem;
	141	unsigned mode;
	142	int score;
	143
	144	elem = tree_entry_extract(&one, &path, &mode);
	145	if (!S_ISDIR(mode))
	146	goto next;
	147	score = score_trees(elem, hash2);
	148	if (*best_score < score) {
	149	char *newpath;
	150	newpath = xmalloc(strlen(base) + strlen(path) + 1);
	151	sprintf(newpath, "%s%s", base, path);
	152	free(*best_match);
	153	*best_match = newpath;
	154	*best_score = score;
	155	}
	156	if (recurse_limit) {
	157	char *newbase;
	158	newbase = xmalloc(strlen(base) + strlen(path) + 2);
	159	sprintf(newbase, "%s%s/", base, path);
	160	match_trees(elem, hash2, best_score, best_match,
	161	newbase, recurse_limit - 1);
	162	free(newbase);
	163	}
	164
	165	next:
	166	update_tree_entry(&one);
	167	}
	168	free(one_buf);
	169	}
	170
	171	/*
	172	* A tree "hash1" has a subdirectory at "prefix". Come up with a
	173	* tree object by replacing it with another tree "hash2".
	174	*/
	175	static int splice_tree(const unsigned char *hash1,
85e51b78	176	const char *prefix,
68faf689 JH	177	const unsigned char *hash2,
	178	unsigned char *result)
	179	{
	180	char *subpath;
	181	int toplen;
	182	char *buf;
	183	unsigned long sz;
	184	struct tree_desc desc;
	185	unsigned char *rewrite_here;
	186	const unsigned char *rewrite_with;
	187	unsigned char subtree[20];
	188	enum object_type type;
	189	int status;
	190
	191	subpath = strchr(prefix, '/');
	192	if (!subpath)
	193	toplen = strlen(prefix);
	194	else {
	195	toplen = subpath - prefix;
	196	subpath++;
	197	}
	198
	199	buf = read_sha1_file(hash1, &type, &sz);
	200	if (!buf)
	201	die("cannot read tree %s", sha1_to_hex(hash1));
	202	init_tree_desc(&desc, buf, sz);
	203
	204	rewrite_here = NULL;
	205	while (desc.size) {
	206	const char *name;
	207	unsigned mode;
	208	const unsigned char *sha1;
	209
	210	sha1 = tree_entry_extract(&desc, &name, &mode);
	211	if (strlen(name) == toplen &&
	212	!memcmp(name, prefix, toplen)) {
	213	if (!S_ISDIR(mode))
	214	die("entry %s in tree %s is not a tree",
	215	name, sha1_to_hex(hash1));
	216	rewrite_here = (unsigned char *) sha1;
	217	break;
	218	}
	219	update_tree_entry(&desc);
	220	}
	221	if (!rewrite_here)
	222	die("entry %.*s not found in tree %s",
	223	toplen, prefix, sha1_to_hex(hash1));
	224	if (subpath) {
	225	status = splice_tree(rewrite_here, subpath, hash2, subtree);
	226	if (status)
	227	return status;
	228	rewrite_with = subtree;
	229	}
	230	else
	231	rewrite_with = hash2;
	232	hashcpy(rewrite_here, rewrite_with);
	233	status = write_sha1_file(buf, sz, tree_type, result);
	234	free(buf);
	235	return status;
	236	}
	237
	238	/*
	239	* We are trying to come up with a merge between one and two that
	240	* results in a tree shape similar to one. The tree two might
241	* correspond to a subtree of one, in which case it needs to be
242	* shifted down by prefixing otherwise empty directories. On the
243	* other hand, it could cover tree one and we might need to pick a
244	* subtree of it.
245	*/
246	void shift_tree(const unsigned char *hash1,
247	const unsigned char *hash2,
248	unsigned char *shifted,
249	int depth_limit)
250	{
251	char *add_prefix;
252	char *del_prefix;
253	int add_score, del_score;
254
85e51b78 JH	255	/*
	256	* NEEDSWORK: this limits the recursion depth to hardcoded
	257	* value '2' to avoid excessive overhead.
	258	*/
	259	if (!depth_limit)
	260	depth_limit = 2;
	261
68faf689 JH	262	add_score = del_score = score_trees(hash1, hash2);
	263	add_prefix = xcalloc(1, 1);
	264	del_prefix = xcalloc(1, 1);
	265
	266	/*
	267	* See if one's subtree resembles two; if so we need to prefix
	268	* two with a few fake trees to match the prefix.
	269	*/
	270	match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
	271
	272	/*
	273	* See if two's subtree resembles one; if so we need to
	274	* pick only subtree of two.
	275	*/
	276	match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
	277
	278	/* Assume we do not have to do any shifting */
	279	hashcpy(shifted, hash2);
	280
	281	if (add_score < del_score) {
	282	/* We need to pick a subtree of two */
	283	unsigned mode;
	284
	285	if (!*del_prefix)
	286	return;
	287
	288	if (get_tree_entry(hash2, del_prefix, shifted, &mode))
	289	die("cannot find path %s in tree %s",
	290	del_prefix, sha1_to_hex(hash2));
	291	return;
	292	}
	293
	294	if (!*add_prefix)
	295	return;
	296
	297	splice_tree(hash1, add_prefix, hash2, shifted);
	298	}
85e51b78 JH	299
	300	/*
	301	* The user says the trees will be shifted by this much.
	302	* Unfortunately we cannot fundamentally tell which one to
	303	* be prefixed, as recursive merge can work in either direction.
	304	*/
	305	void shift_tree_by(const unsigned char *hash1,
	306	const unsigned char *hash2,
	307	unsigned char *shifted,
	308	const char *shift_prefix)
	309	{
	310	unsigned char sub1[20], sub2[20];
	311	unsigned mode1, mode2;
	312	unsigned candidate = 0;
	313
	314	/* Can hash2 be a tree at shift_prefix in tree hash1? */
	315	if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
	316	S_ISDIR(mode1))
	317	candidate \|= 1;
	318
	319	/* Can hash1 be a tree at shift_prefix in tree hash2? */
	320	if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
	321	S_ISDIR(mode2))
	322	candidate \|= 2;
	323
	324	if (candidate == 3) {
	325	/* Both are plausible -- we need to evaluate the score */
	326	int best_score = score_trees(hash1, hash2);
	327	int score;
	328
	329	candidate = 0;
	330	score = score_trees(sub1, hash2);
	331	if (score > best_score) {
	332	candidate = 1;
	333	best_score = score;
	334	}
	335	score = score_trees(sub2, hash1);
	336	if (score > best_score)
	337	candidate = 2;
	338	}
	339
	340	if (!candidate) {
	341	/* Neither is plausible -- do not shift */
	342	hashcpy(shifted, hash2);
	343	return;
	344	}
	345
	346	if (candidate == 1)
	347	/*
	348	* shift tree2 down by adding shift_prefix above it
	349	* to match tree1.
	350	*/
	351	splice_tree(hash1, shift_prefix, hash2, shifted);
	352	else
	353	/*
	354	* shift tree2 up by removing shift_prefix from it
	355	* to match tree1.
	356	*/
	357	hashcpy(shifted, sub2);
	358	}