git

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#define USE_THE_REPOSITORY_VARIABLE
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#include "git-compat-util.h"
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#include "hex.h"
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#include "match-trees.h"
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#include "strbuf.h"
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#include "tree.h"
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#include "tree-walk.h"
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#include "object-store-ll.h"
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static int score_missing(unsigned mode)
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{
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	int score;
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	if (S_ISDIR(mode))
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		score = -1000;
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	else if (S_ISLNK(mode))
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		score = -500;
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	else
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		score = -50;
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	return score;
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}
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static int score_differs(unsigned mode1, unsigned mode2)
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{
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	int score;
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	if (S_ISDIR(mode1) != S_ISDIR(mode2))
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		score = -100;
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	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
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		score = -50;
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	else
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		score = -5;
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	return score;
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}
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static int score_matches(unsigned mode1, unsigned mode2)
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{
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	int score;
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	/* Heh, we found SHA-1 collisions between different kind of objects */
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	if (S_ISDIR(mode1) != S_ISDIR(mode2))
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		score = -100;
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	else if (S_ISLNK(mode1) != S_ISLNK(mode2))
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		score = -50;
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	else if (S_ISDIR(mode1))
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		score = 1000;
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	else if (S_ISLNK(mode1))
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		score = 500;
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	else
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		score = 250;
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	return score;
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}
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static void *fill_tree_desc_strict(struct tree_desc *desc,
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				   const struct object_id *hash)
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{
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	void *buffer;
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	enum object_type type;
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	unsigned long size;
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	buffer = repo_read_object_file(the_repository, hash, &type, &size);
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	if (!buffer)
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		die("unable to read tree (%s)", oid_to_hex(hash));
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	if (type != OBJ_TREE)
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		die("%s is not a tree", oid_to_hex(hash));
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	init_tree_desc(desc, hash, buffer, size);
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	return buffer;
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}
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static int base_name_entries_compare(const struct name_entry *a,
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				     const struct name_entry *b)
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{
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	return base_name_compare(a->path, tree_entry_len(a), a->mode,
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				 b->path, tree_entry_len(b), b->mode);
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}
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/*
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 * Inspect two trees, and give a score that tells how similar they are.
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 */
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static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
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{
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	struct tree_desc one;
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	struct tree_desc two;
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	void *one_buf = fill_tree_desc_strict(&one, hash1);
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	void *two_buf = fill_tree_desc_strict(&two, hash2);
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	int score = 0;
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	for (;;) {
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		int cmp;
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		if (one.size && two.size)
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			cmp = base_name_entries_compare(&one.entry, &two.entry);
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		else if (one.size)
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			/* two lacks this entry */
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			cmp = -1;
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		else if (two.size)
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			/* two has more entries */
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			cmp = 1;
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		else
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			break;
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		if (cmp < 0) {
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			/* path1 does not appear in two */
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			score += score_missing(one.entry.mode);
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			update_tree_entry(&one);
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		} else if (cmp > 0) {
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			/* path2 does not appear in one */
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			score += score_missing(two.entry.mode);
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			update_tree_entry(&two);
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		} else {
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			/* path appears in both */
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			if (!oideq(&one.entry.oid, &two.entry.oid)) {
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				/* they are different */
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				score += score_differs(one.entry.mode,
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						       two.entry.mode);
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			} else {
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				/* same subtree or blob */
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				score += score_matches(one.entry.mode,
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						       two.entry.mode);
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			}
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			update_tree_entry(&one);
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			update_tree_entry(&two);
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		}
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	}
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	free(one_buf);
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	free(two_buf);
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	return score;
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}
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/*
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 * Match one itself and its subtrees with two and pick the best match.
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 */
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static void match_trees(const struct object_id *hash1,
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			const struct object_id *hash2,
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			int *best_score,
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			char **best_match,
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			const char *base,
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			int recurse_limit)
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{
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	struct tree_desc one;
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	void *one_buf = fill_tree_desc_strict(&one, hash1);
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	while (one.size) {
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		const char *path;
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		const struct object_id *elem;
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		unsigned short mode;
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		int score;
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		elem = tree_entry_extract(&one, &path, &mode);
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		if (!S_ISDIR(mode))
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			goto next;
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		score = score_trees(elem, hash2);
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		if (*best_score < score) {
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			free(*best_match);
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			*best_match = xstrfmt("%s%s", base, path);
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			*best_score = score;
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		}
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		if (recurse_limit) {
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			char *newbase = xstrfmt("%s%s/", base, path);
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			match_trees(elem, hash2, best_score, best_match,
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				    newbase, recurse_limit - 1);
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			free(newbase);
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		}
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	next:
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		update_tree_entry(&one);
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	}
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	free(one_buf);
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}
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/*
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 * A tree "oid1" has a subdirectory at "prefix".  Come up with a tree object by
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 * replacing it with another tree "oid2".
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 */
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static int splice_tree(const struct object_id *oid1, const char *prefix,
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		       const struct object_id *oid2, struct object_id *result)
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{
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	char *subpath;
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	int toplen;
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	char *buf;
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	unsigned long sz;
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	struct tree_desc desc;
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	unsigned char *rewrite_here;
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	const struct object_id *rewrite_with;
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	struct object_id subtree;
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	enum object_type type;
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	int status;
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	subpath = strchrnul(prefix, '/');
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	toplen = subpath - prefix;
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	if (*subpath)
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		subpath++;
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	buf = repo_read_object_file(the_repository, oid1, &type, &sz);
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	if (!buf)
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		die("cannot read tree %s", oid_to_hex(oid1));
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	init_tree_desc(&desc, oid1, buf, sz);
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	rewrite_here = NULL;
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	while (desc.size) {
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		const char *name;
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		unsigned short mode;
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		tree_entry_extract(&desc, &name, &mode);
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		if (strlen(name) == toplen &&
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		    !memcmp(name, prefix, toplen)) {
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			if (!S_ISDIR(mode))
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				die("entry %s in tree %s is not a tree", name,
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				    oid_to_hex(oid1));
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			/*
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			 * We cast here for two reasons:
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			 *
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			 *   - to flip the "char *" (for the path) to "unsigned
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			 *     char *" (for the hash stored after it)
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			 *
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			 *   - to discard the "const"; this is OK because we
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			 *     know it points into our non-const "buf"
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			 */
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			rewrite_here = (unsigned char *)(desc.entry.path +
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							 strlen(desc.entry.path) +
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							 1);
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			break;
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		}
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		update_tree_entry(&desc);
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	}
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	if (!rewrite_here)
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		die("entry %.*s not found in tree %s", toplen, prefix,
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		    oid_to_hex(oid1));
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	if (*subpath) {
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		struct object_id tree_oid;
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		oidread(&tree_oid, rewrite_here, the_repository->hash_algo);
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		status = splice_tree(&tree_oid, subpath, oid2, &subtree);
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		if (status)
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			return status;
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		rewrite_with = &subtree;
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	} else {
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		rewrite_with = oid2;
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	}
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	hashcpy(rewrite_here, rewrite_with->hash, the_repository->hash_algo);
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	status = write_object_file(buf, sz, OBJ_TREE, result);
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	free(buf);
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	return status;
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}
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/*
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 * We are trying to come up with a merge between one and two that
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 * results in a tree shape similar to one.  The tree two might
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 * correspond to a subtree of one, in which case it needs to be
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 * shifted down by prefixing otherwise empty directories.  On the
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 * other hand, it could cover tree one and we might need to pick a
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 * subtree of it.
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 */
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void shift_tree(struct repository *r,
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		const struct object_id *hash1,
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		const struct object_id *hash2,
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		struct object_id *shifted,
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		int depth_limit)
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{
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	char *add_prefix;
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	char *del_prefix;
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	int add_score, del_score;
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	/*
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	 * NEEDSWORK: this limits the recursion depth to hardcoded
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	 * value '2' to avoid excessive overhead.
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	 */
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	if (!depth_limit)
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		depth_limit = 2;
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	add_score = del_score = score_trees(hash1, hash2);
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	add_prefix = xcalloc(1, 1);
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	del_prefix = xcalloc(1, 1);
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	/*
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	 * See if one's subtree resembles two; if so we need to prefix
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	 * two with a few fake trees to match the prefix.
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	 */
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	match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
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	/*
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	 * See if two's subtree resembles one; if so we need to
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	 * pick only subtree of two.
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	 */
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	match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
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	/* Assume we do not have to do any shifting */
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	oidcpy(shifted, hash2);
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	if (add_score < del_score) {
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		/* We need to pick a subtree of two */
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		unsigned short mode;
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		if (!*del_prefix)
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			return;
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		if (get_tree_entry(r, hash2, del_prefix, shifted, &mode))
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			die("cannot find path %s in tree %s",
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			    del_prefix, oid_to_hex(hash2));
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		return;
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	}
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	if (!*add_prefix)
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		return;
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	splice_tree(hash1, add_prefix, hash2, shifted);
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}
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/*
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 * The user says the trees will be shifted by this much.
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 * Unfortunately we cannot fundamentally tell which one to
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 * be prefixed, as recursive merge can work in either direction.
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 */
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void shift_tree_by(struct repository *r,
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		   const struct object_id *hash1,
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		   const struct object_id *hash2,
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		   struct object_id *shifted,
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		   const char *shift_prefix)
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{
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	struct object_id sub1, sub2;
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	unsigned short mode1, mode2;
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	unsigned candidate = 0;
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	/* Can hash2 be a tree at shift_prefix in tree hash1? */
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	if (!get_tree_entry(r, hash1, shift_prefix, &sub1, &mode1) &&
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	    S_ISDIR(mode1))
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		candidate |= 1;
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	/* Can hash1 be a tree at shift_prefix in tree hash2? */
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	if (!get_tree_entry(r, hash2, shift_prefix, &sub2, &mode2) &&
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	    S_ISDIR(mode2))
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		candidate |= 2;
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	if (candidate == 3) {
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		/* Both are plausible -- we need to evaluate the score */
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		int best_score = score_trees(hash1, hash2);
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		int score;
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		candidate = 0;
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		score = score_trees(&sub1, hash2);
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		if (score > best_score) {
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			candidate = 1;
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			best_score = score;
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		}
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		score = score_trees(&sub2, hash1);
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		if (score > best_score)
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			candidate = 2;
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	}
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	if (!candidate) {
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		/* Neither is plausible -- do not shift */
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		oidcpy(shifted, hash2);
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		return;
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	}
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	if (candidate == 1)
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		/*
360
		 * shift tree2 down by adding shift_prefix above it
361
		 * to match tree1.
362
		 */
363
		splice_tree(hash1, shift_prefix, hash2, shifted);
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	else
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		/*
366
		 * shift tree2 up by removing shift_prefix from it
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		 * to match tree1.
368
		 */
369
		oidcpy(shifted, &sub2);
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}
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