Function shift_tree

match-trees.c:262–319

* 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. */

 * subtree of it.
 */
void shift_tree(struct repository *r,
		const struct object_id *hash1,
		const struct object_id *hash2,
		struct object_id *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(r, 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(r, 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(r, hash2, hash1, &del_score, &del_prefix, "", depth_limit);

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

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

		if (!*del_prefix)
			goto out;

		if (get_tree_entry(r, hash2, del_prefix, shifted, &mode))
			die("cannot find path %s in tree %s",
			    del_prefix, oid_to_hex(hash2));
		goto out;
	}

	if (!*add_prefix)
		goto out;

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

out:
	free(add_prefix);
	free(del_prefix);
}