cocci: remove 'unused.cocci'
[git.git] / match-trees.c
blob5877fc64a8f93612ba65bfa19651d4e392695c55
1 #include "cache.h"
2 #include "hex.h"
3 #include "tree.h"
4 #include "tree-walk.h"
5 #include "object-store.h"
7 static int score_missing(unsigned mode)
9 int score;
11 if (S_ISDIR(mode))
12 score = -1000;
13 else if (S_ISLNK(mode))
14 score = -500;
15 else
16 score = -50;
17 return score;
20 static int score_differs(unsigned mode1, unsigned mode2)
22 int score;
24 if (S_ISDIR(mode1) != S_ISDIR(mode2))
25 score = -100;
26 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
27 score = -50;
28 else
29 score = -5;
30 return score;
33 static int score_matches(unsigned mode1, unsigned mode2)
35 int score;
37 /* Heh, we found SHA-1 collisions between different kind of objects */
38 if (S_ISDIR(mode1) != S_ISDIR(mode2))
39 score = -100;
40 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
41 score = -50;
43 else if (S_ISDIR(mode1))
44 score = 1000;
45 else if (S_ISLNK(mode1))
46 score = 500;
47 else
48 score = 250;
49 return score;
52 static void *fill_tree_desc_strict(struct tree_desc *desc,
53 const struct object_id *hash)
55 void *buffer;
56 enum object_type type;
57 unsigned long size;
59 buffer = repo_read_object_file(the_repository, hash, &type, &size);
60 if (!buffer)
61 die("unable to read tree (%s)", oid_to_hex(hash));
62 if (type != OBJ_TREE)
63 die("%s is not a tree", oid_to_hex(hash));
64 init_tree_desc(desc, buffer, size);
65 return buffer;
68 static int base_name_entries_compare(const struct name_entry *a,
69 const struct name_entry *b)
71 return base_name_compare(a->path, tree_entry_len(a), a->mode,
72 b->path, tree_entry_len(b), b->mode);
76 * Inspect two trees, and give a score that tells how similar they are.
78 static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
80 struct tree_desc one;
81 struct tree_desc two;
82 void *one_buf = fill_tree_desc_strict(&one, hash1);
83 void *two_buf = fill_tree_desc_strict(&two, hash2);
84 int score = 0;
86 for (;;) {
87 int cmp;
89 if (one.size && two.size)
90 cmp = base_name_entries_compare(&one.entry, &two.entry);
91 else if (one.size)
92 /* two lacks this entry */
93 cmp = -1;
94 else if (two.size)
95 /* two has more entries */
96 cmp = 1;
97 else
98 break;
100 if (cmp < 0) {
101 /* path1 does not appear in two */
102 score += score_missing(one.entry.mode);
103 update_tree_entry(&one);
104 } else if (cmp > 0) {
105 /* path2 does not appear in one */
106 score += score_missing(two.entry.mode);
107 update_tree_entry(&two);
108 } else {
109 /* path appears in both */
110 if (!oideq(&one.entry.oid, &two.entry.oid)) {
111 /* they are different */
112 score += score_differs(one.entry.mode,
113 two.entry.mode);
114 } else {
115 /* same subtree or blob */
116 score += score_matches(one.entry.mode,
117 two.entry.mode);
119 update_tree_entry(&one);
120 update_tree_entry(&two);
123 free(one_buf);
124 free(two_buf);
125 return score;
129 * Match one itself and its subtrees with two and pick the best match.
131 static void match_trees(const struct object_id *hash1,
132 const struct object_id *hash2,
133 int *best_score,
134 char **best_match,
135 const char *base,
136 int recurse_limit)
138 struct tree_desc one;
139 void *one_buf = fill_tree_desc_strict(&one, hash1);
141 while (one.size) {
142 const char *path;
143 const struct object_id *elem;
144 unsigned short mode;
145 int score;
147 elem = tree_entry_extract(&one, &path, &mode);
148 if (!S_ISDIR(mode))
149 goto next;
150 score = score_trees(elem, hash2);
151 if (*best_score < score) {
152 free(*best_match);
153 *best_match = xstrfmt("%s%s", base, path);
154 *best_score = score;
156 if (recurse_limit) {
157 char *newbase = xstrfmt("%s%s/", base, path);
158 match_trees(elem, hash2, best_score, best_match,
159 newbase, recurse_limit - 1);
160 free(newbase);
163 next:
164 update_tree_entry(&one);
166 free(one_buf);
170 * A tree "oid1" has a subdirectory at "prefix". Come up with a tree object by
171 * replacing it with another tree "oid2".
173 static int splice_tree(const struct object_id *oid1, const char *prefix,
174 const struct object_id *oid2, struct object_id *result)
176 char *subpath;
177 int toplen;
178 char *buf;
179 unsigned long sz;
180 struct tree_desc desc;
181 unsigned char *rewrite_here;
182 const struct object_id *rewrite_with;
183 struct object_id subtree;
184 enum object_type type;
185 int status;
187 subpath = strchrnul(prefix, '/');
188 toplen = subpath - prefix;
189 if (*subpath)
190 subpath++;
192 buf = repo_read_object_file(the_repository, oid1, &type, &sz);
193 if (!buf)
194 die("cannot read tree %s", oid_to_hex(oid1));
195 init_tree_desc(&desc, buf, sz);
197 rewrite_here = NULL;
198 while (desc.size) {
199 const char *name;
200 unsigned short mode;
202 tree_entry_extract(&desc, &name, &mode);
203 if (strlen(name) == toplen &&
204 !memcmp(name, prefix, toplen)) {
205 if (!S_ISDIR(mode))
206 die("entry %s in tree %s is not a tree", name,
207 oid_to_hex(oid1));
210 * We cast here for two reasons:
212 * - to flip the "char *" (for the path) to "unsigned
213 * char *" (for the hash stored after it)
215 * - to discard the "const"; this is OK because we
216 * know it points into our non-const "buf"
218 rewrite_here = (unsigned char *)(desc.entry.path +
219 strlen(desc.entry.path) +
221 break;
223 update_tree_entry(&desc);
225 if (!rewrite_here)
226 die("entry %.*s not found in tree %s", toplen, prefix,
227 oid_to_hex(oid1));
228 if (*subpath) {
229 struct object_id tree_oid;
230 oidread(&tree_oid, rewrite_here);
231 status = splice_tree(&tree_oid, subpath, oid2, &subtree);
232 if (status)
233 return status;
234 rewrite_with = &subtree;
235 } else {
236 rewrite_with = oid2;
238 hashcpy(rewrite_here, rewrite_with->hash);
239 status = write_object_file(buf, sz, OBJ_TREE, result);
240 free(buf);
241 return status;
245 * We are trying to come up with a merge between one and two that
246 * results in a tree shape similar to one. The tree two might
247 * correspond to a subtree of one, in which case it needs to be
248 * shifted down by prefixing otherwise empty directories. On the
249 * other hand, it could cover tree one and we might need to pick a
250 * subtree of it.
252 void shift_tree(struct repository *r,
253 const struct object_id *hash1,
254 const struct object_id *hash2,
255 struct object_id *shifted,
256 int depth_limit)
258 char *add_prefix;
259 char *del_prefix;
260 int add_score, del_score;
263 * NEEDSWORK: this limits the recursion depth to hardcoded
264 * value '2' to avoid excessive overhead.
266 if (!depth_limit)
267 depth_limit = 2;
269 add_score = del_score = score_trees(hash1, hash2);
270 add_prefix = xcalloc(1, 1);
271 del_prefix = xcalloc(1, 1);
274 * See if one's subtree resembles two; if so we need to prefix
275 * two with a few fake trees to match the prefix.
277 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
280 * See if two's subtree resembles one; if so we need to
281 * pick only subtree of two.
283 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
285 /* Assume we do not have to do any shifting */
286 oidcpy(shifted, hash2);
288 if (add_score < del_score) {
289 /* We need to pick a subtree of two */
290 unsigned short mode;
292 if (!*del_prefix)
293 return;
295 if (get_tree_entry(r, hash2, del_prefix, shifted, &mode))
296 die("cannot find path %s in tree %s",
297 del_prefix, oid_to_hex(hash2));
298 return;
301 if (!*add_prefix)
302 return;
304 splice_tree(hash1, add_prefix, hash2, shifted);
308 * The user says the trees will be shifted by this much.
309 * Unfortunately we cannot fundamentally tell which one to
310 * be prefixed, as recursive merge can work in either direction.
312 void shift_tree_by(struct repository *r,
313 const struct object_id *hash1,
314 const struct object_id *hash2,
315 struct object_id *shifted,
316 const char *shift_prefix)
318 struct object_id sub1, sub2;
319 unsigned short mode1, mode2;
320 unsigned candidate = 0;
322 /* Can hash2 be a tree at shift_prefix in tree hash1? */
323 if (!get_tree_entry(r, hash1, shift_prefix, &sub1, &mode1) &&
324 S_ISDIR(mode1))
325 candidate |= 1;
327 /* Can hash1 be a tree at shift_prefix in tree hash2? */
328 if (!get_tree_entry(r, hash2, shift_prefix, &sub2, &mode2) &&
329 S_ISDIR(mode2))
330 candidate |= 2;
332 if (candidate == 3) {
333 /* Both are plausible -- we need to evaluate the score */
334 int best_score = score_trees(hash1, hash2);
335 int score;
337 candidate = 0;
338 score = score_trees(&sub1, hash2);
339 if (score > best_score) {
340 candidate = 1;
341 best_score = score;
343 score = score_trees(&sub2, hash1);
344 if (score > best_score)
345 candidate = 2;
348 if (!candidate) {
349 /* Neither is plausible -- do not shift */
350 oidcpy(shifted, hash2);
351 return;
354 if (candidate == 1)
356 * shift tree2 down by adding shift_prefix above it
357 * to match tree1.
359 splice_tree(hash1, shift_prefix, hash2, shifted);
360 else
362 * shift tree2 up by removing shift_prefix from it
363 * to match tree1.
365 oidcpy(shifted, &sub2);