Start preparing for 1.8.4.2
[alt-git.git] / match-trees.c
blob7873cdec581eea66feab06c22b83ef7c27c7c5b6
1 #include "cache.h"
2 #include "tree.h"
3 #include "tree-walk.h"
5 static int score_missing(unsigned mode, const char *path)
7 int score;
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;
18 static int score_differs(unsigned mode1, unsigned mode2, const char *path)
20 int score;
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;
31 static int score_matches(unsigned mode1, unsigned mode2, const char *path)
33 int score;
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;
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;
50 static void *fill_tree_desc_strict(struct tree_desc *desc,
51 const unsigned char *hash)
53 void *buffer;
54 enum object_type type;
55 unsigned long size;
57 buffer = read_sha1_file(hash, &type, &size);
58 if (!buffer)
59 die("unable to read tree (%s)", sha1_to_hex(hash));
60 if (type != OBJ_TREE)
61 die("%s is not a tree", sha1_to_hex(hash));
62 init_tree_desc(desc, buffer, size);
63 return buffer;
66 static int base_name_entries_compare(const struct name_entry *a,
67 const struct name_entry *b)
69 return base_name_compare(a->path, tree_entry_len(a), a->mode,
70 b->path, tree_entry_len(b), b->mode);
74 * Inspect two trees, and give a score that tells how similar they are.
76 static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
78 struct tree_desc one;
79 struct tree_desc two;
80 void *one_buf = fill_tree_desc_strict(&one, hash1);
81 void *two_buf = fill_tree_desc_strict(&two, hash2);
82 int score = 0;
84 for (;;) {
85 struct name_entry e1, e2;
86 int got_entry_from_one = tree_entry(&one, &e1);
87 int got_entry_from_two = tree_entry(&two, &e2);
88 int cmp;
90 if (got_entry_from_one && got_entry_from_two)
91 cmp = base_name_entries_compare(&e1, &e2);
92 else if (got_entry_from_one)
93 /* two lacks this entry */
94 cmp = -1;
95 else if (got_entry_from_two)
96 /* two has more entries */
97 cmp = 1;
98 else
99 break;
101 if (cmp < 0)
102 /* path1 does not appear in two */
103 score += score_missing(e1.mode, e1.path);
104 else if (cmp > 0)
105 /* path2 does not appear in one */
106 score += score_missing(e2.mode, e2.path);
107 else if (hashcmp(e1.sha1, e2.sha1))
108 /* they are different */
109 score += score_differs(e1.mode, e2.mode, e1.path);
110 else
111 /* same subtree or blob */
112 score += score_matches(e1.mode, e2.mode, e1.path);
114 free(one_buf);
115 free(two_buf);
116 return score;
120 * Match one itself and its subtrees with two and pick the best match.
122 static void match_trees(const unsigned char *hash1,
123 const unsigned char *hash2,
124 int *best_score,
125 char **best_match,
126 const char *base,
127 int recurse_limit)
129 struct tree_desc one;
130 void *one_buf = fill_tree_desc_strict(&one, hash1);
132 while (one.size) {
133 const char *path;
134 const unsigned char *elem;
135 unsigned mode;
136 int score;
138 elem = tree_entry_extract(&one, &path, &mode);
139 if (!S_ISDIR(mode))
140 goto next;
141 score = score_trees(elem, hash2);
142 if (*best_score < score) {
143 char *newpath;
144 newpath = xmalloc(strlen(base) + strlen(path) + 1);
145 sprintf(newpath, "%s%s", base, path);
146 free(*best_match);
147 *best_match = newpath;
148 *best_score = score;
150 if (recurse_limit) {
151 char *newbase;
152 newbase = xmalloc(strlen(base) + strlen(path) + 2);
153 sprintf(newbase, "%s%s/", base, path);
154 match_trees(elem, hash2, best_score, best_match,
155 newbase, recurse_limit - 1);
156 free(newbase);
159 next:
160 update_tree_entry(&one);
162 free(one_buf);
166 * A tree "hash1" has a subdirectory at "prefix". Come up with a
167 * tree object by replacing it with another tree "hash2".
169 static int splice_tree(const unsigned char *hash1,
170 const char *prefix,
171 const unsigned char *hash2,
172 unsigned char *result)
174 char *subpath;
175 int toplen;
176 char *buf;
177 unsigned long sz;
178 struct tree_desc desc;
179 unsigned char *rewrite_here;
180 const unsigned char *rewrite_with;
181 unsigned char subtree[20];
182 enum object_type type;
183 int status;
185 subpath = strchr(prefix, '/');
186 if (!subpath)
187 toplen = strlen(prefix);
188 else {
189 toplen = subpath - prefix;
190 subpath++;
193 buf = read_sha1_file(hash1, &type, &sz);
194 if (!buf)
195 die("cannot read tree %s", sha1_to_hex(hash1));
196 init_tree_desc(&desc, buf, sz);
198 rewrite_here = NULL;
199 while (desc.size) {
200 const char *name;
201 unsigned mode;
202 const unsigned char *sha1;
204 sha1 = tree_entry_extract(&desc, &name, &mode);
205 if (strlen(name) == toplen &&
206 !memcmp(name, prefix, toplen)) {
207 if (!S_ISDIR(mode))
208 die("entry %s in tree %s is not a tree",
209 name, sha1_to_hex(hash1));
210 rewrite_here = (unsigned char *) sha1;
211 break;
213 update_tree_entry(&desc);
215 if (!rewrite_here)
216 die("entry %.*s not found in tree %s",
217 toplen, prefix, sha1_to_hex(hash1));
218 if (subpath) {
219 status = splice_tree(rewrite_here, subpath, hash2, subtree);
220 if (status)
221 return status;
222 rewrite_with = subtree;
224 else
225 rewrite_with = hash2;
226 hashcpy(rewrite_here, rewrite_with);
227 status = write_sha1_file(buf, sz, tree_type, result);
228 free(buf);
229 return status;
233 * We are trying to come up with a merge between one and two that
234 * results in a tree shape similar to one. The tree two might
235 * correspond to a subtree of one, in which case it needs to be
236 * shifted down by prefixing otherwise empty directories. On the
237 * other hand, it could cover tree one and we might need to pick a
238 * subtree of it.
240 void shift_tree(const unsigned char *hash1,
241 const unsigned char *hash2,
242 unsigned char *shifted,
243 int depth_limit)
245 char *add_prefix;
246 char *del_prefix;
247 int add_score, del_score;
250 * NEEDSWORK: this limits the recursion depth to hardcoded
251 * value '2' to avoid excessive overhead.
253 if (!depth_limit)
254 depth_limit = 2;
256 add_score = del_score = score_trees(hash1, hash2);
257 add_prefix = xcalloc(1, 1);
258 del_prefix = xcalloc(1, 1);
261 * See if one's subtree resembles two; if so we need to prefix
262 * two with a few fake trees to match the prefix.
264 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
267 * See if two's subtree resembles one; if so we need to
268 * pick only subtree of two.
270 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
272 /* Assume we do not have to do any shifting */
273 hashcpy(shifted, hash2);
275 if (add_score < del_score) {
276 /* We need to pick a subtree of two */
277 unsigned mode;
279 if (!*del_prefix)
280 return;
282 if (get_tree_entry(hash2, del_prefix, shifted, &mode))
283 die("cannot find path %s in tree %s",
284 del_prefix, sha1_to_hex(hash2));
285 return;
288 if (!*add_prefix)
289 return;
291 splice_tree(hash1, add_prefix, hash2, shifted);
295 * The user says the trees will be shifted by this much.
296 * Unfortunately we cannot fundamentally tell which one to
297 * be prefixed, as recursive merge can work in either direction.
299 void shift_tree_by(const unsigned char *hash1,
300 const unsigned char *hash2,
301 unsigned char *shifted,
302 const char *shift_prefix)
304 unsigned char sub1[20], sub2[20];
305 unsigned mode1, mode2;
306 unsigned candidate = 0;
308 /* Can hash2 be a tree at shift_prefix in tree hash1? */
309 if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
310 S_ISDIR(mode1))
311 candidate |= 1;
313 /* Can hash1 be a tree at shift_prefix in tree hash2? */
314 if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
315 S_ISDIR(mode2))
316 candidate |= 2;
318 if (candidate == 3) {
319 /* Both are plausible -- we need to evaluate the score */
320 int best_score = score_trees(hash1, hash2);
321 int score;
323 candidate = 0;
324 score = score_trees(sub1, hash2);
325 if (score > best_score) {
326 candidate = 1;
327 best_score = score;
329 score = score_trees(sub2, hash1);
330 if (score > best_score)
331 candidate = 2;
334 if (!candidate) {
335 /* Neither is plausible -- do not shift */
336 hashcpy(shifted, hash2);
337 return;
340 if (candidate == 1)
342 * shift tree2 down by adding shift_prefix above it
343 * to match tree1.
345 splice_tree(hash1, shift_prefix, hash2, shifted);
346 else
348 * shift tree2 up by removing shift_prefix from it
349 * to match tree1.
351 hashcpy(shifted, sub2);