| #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 void *fill_tree_desc_strict(struct tree_desc *desc, |
| const unsigned char *hash) |
| { |
| void *buffer; |
| enum object_type type; |
| unsigned long size; |
| |
| buffer = read_sha1_file(hash, &type, &size); |
| if (!buffer) |
| die("unable to read tree (%s)", sha1_to_hex(hash)); |
| if (type != OBJ_TREE) |
| die("%s is not a tree", sha1_to_hex(hash)); |
| init_tree_desc(desc, buffer, size); |
| return buffer; |
| } |
| |
| 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 = fill_tree_desc_strict(&one, hash1); |
| void *two_buf = fill_tree_desc_strict(&two, hash2); |
| int score = 0; |
| |
| 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 = fill_tree_desc_strict(&one, hash1); |
| |
| 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 = strchrnul(prefix, '/'); |
| toplen = subpath - prefix; |
| if (*subpath) |
| 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); |
| } |