Merge branch 'rb/hpe'
[git.git] / match-trees.c
blob2b6d31ef9d35d9422e7ef90792651dcb7a2f9189
1 #include "cache.h"
2 #include "tree.h"
3 #include "tree-walk.h"
4 #include "object-store.h"
6 static int score_missing(unsigned mode, const char *path)
8 int score;
10 if (S_ISDIR(mode))
11 score = -1000;
12 else if (S_ISLNK(mode))
13 score = -500;
14 else
15 score = -50;
16 return score;
19 static int score_differs(unsigned mode1, unsigned mode2, const char *path)
21 int score;
23 if (S_ISDIR(mode1) != S_ISDIR(mode2))
24 score = -100;
25 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
26 score = -50;
27 else
28 score = -5;
29 return score;
32 static int score_matches(unsigned mode1, unsigned mode2, const char *path)
34 int score;
36 /* Heh, we found SHA-1 collisions between different kind of objects */
37 if (S_ISDIR(mode1) != S_ISDIR(mode2))
38 score = -100;
39 else if (S_ISLNK(mode1) != S_ISLNK(mode2))
40 score = -50;
42 else if (S_ISDIR(mode1))
43 score = 1000;
44 else if (S_ISLNK(mode1))
45 score = 500;
46 else
47 score = 250;
48 return score;
51 static void *fill_tree_desc_strict(struct tree_desc *desc,
52 const struct object_id *hash)
54 void *buffer;
55 enum object_type type;
56 unsigned long size;
58 buffer = read_object_file(hash, &type, &size);
59 if (!buffer)
60 die("unable to read tree (%s)", oid_to_hex(hash));
61 if (type != OBJ_TREE)
62 die("%s is not a tree", oid_to_hex(hash));
63 init_tree_desc(desc, buffer, size);
64 return buffer;
67 static int base_name_entries_compare(const struct name_entry *a,
68 const struct name_entry *b)
70 return base_name_compare(a->path, tree_entry_len(a), a->mode,
71 b->path, tree_entry_len(b), b->mode);
75 * Inspect two trees, and give a score that tells how similar they are.
77 static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
79 struct tree_desc one;
80 struct tree_desc two;
81 void *one_buf = fill_tree_desc_strict(&one, hash1);
82 void *two_buf = fill_tree_desc_strict(&two, hash2);
83 int score = 0;
85 for (;;) {
86 int cmp;
88 if (one.size && two.size)
89 cmp = base_name_entries_compare(&one.entry, &two.entry);
90 else if (one.size)
91 /* two lacks this entry */
92 cmp = -1;
93 else if (two.size)
94 /* two has more entries */
95 cmp = 1;
96 else
97 break;
99 if (cmp < 0) {
100 /* path1 does not appear in two */
101 score += score_missing(one.entry.mode, one.entry.path);
102 update_tree_entry(&one);
103 } else if (cmp > 0) {
104 /* path2 does not appear in one */
105 score += score_missing(two.entry.mode, two.entry.path);
106 update_tree_entry(&two);
107 } else {
108 /* path appears in both */
109 if (!oideq(one.entry.oid, two.entry.oid)) {
110 /* they are different */
111 score += score_differs(one.entry.mode,
112 two.entry.mode,
113 one.entry.path);
114 } else {
115 /* same subtree or blob */
116 score += score_matches(one.entry.mode,
117 two.entry.mode,
118 one.entry.path);
120 update_tree_entry(&one);
121 update_tree_entry(&two);
124 free(one_buf);
125 free(two_buf);
126 return score;
130 * Match one itself and its subtrees with two and pick the best match.
132 static void match_trees(const struct object_id *hash1,
133 const struct object_id *hash2,
134 int *best_score,
135 char **best_match,
136 const char *base,
137 int recurse_limit)
139 struct tree_desc one;
140 void *one_buf = fill_tree_desc_strict(&one, hash1);
142 while (one.size) {
143 const char *path;
144 const struct object_id *elem;
145 unsigned mode;
146 int score;
148 elem = tree_entry_extract(&one, &path, &mode);
149 if (!S_ISDIR(mode))
150 goto next;
151 score = score_trees(elem, hash2);
152 if (*best_score < score) {
153 free(*best_match);
154 *best_match = xstrfmt("%s%s", base, path);
155 *best_score = score;
157 if (recurse_limit) {
158 char *newbase = xstrfmt("%s%s/", base, path);
159 match_trees(elem, hash2, best_score, best_match,
160 newbase, recurse_limit - 1);
161 free(newbase);
164 next:
165 update_tree_entry(&one);
167 free(one_buf);
171 * A tree "oid1" has a subdirectory at "prefix". Come up with a tree object by
172 * replacing it with another tree "oid2".
174 static int splice_tree(const struct object_id *oid1, const char *prefix,
175 const struct object_id *oid2, struct object_id *result)
177 char *subpath;
178 int toplen;
179 char *buf;
180 unsigned long sz;
181 struct tree_desc desc;
182 struct object_id *rewrite_here;
183 const struct object_id *rewrite_with;
184 struct object_id subtree;
185 enum object_type type;
186 int status;
188 subpath = strchrnul(prefix, '/');
189 toplen = subpath - prefix;
190 if (*subpath)
191 subpath++;
193 buf = read_object_file(oid1, &type, &sz);
194 if (!buf)
195 die("cannot read tree %s", oid_to_hex(oid1));
196 init_tree_desc(&desc, buf, sz);
198 rewrite_here = NULL;
199 while (desc.size) {
200 const char *name;
201 unsigned mode;
202 const struct object_id *oid;
204 oid = 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", name,
209 oid_to_hex(oid1));
210 rewrite_here = (struct object_id *)oid;
211 break;
213 update_tree_entry(&desc);
215 if (!rewrite_here)
216 die("entry %.*s not found in tree %s", toplen, prefix,
217 oid_to_hex(oid1));
218 if (*subpath) {
219 status = splice_tree(rewrite_here, subpath, oid2, &subtree);
220 if (status)
221 return status;
222 rewrite_with = &subtree;
223 } else {
224 rewrite_with = oid2;
226 oidcpy(rewrite_here, rewrite_with);
227 status = write_object_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 struct object_id *hash1,
241 const struct object_id *hash2,
242 struct object_id *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 oidcpy(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, oid_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 struct object_id *hash1,
300 const struct object_id *hash2,
301 struct object_id *shifted,
302 const char *shift_prefix)
304 struct object_id sub1, sub2;
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 oidcpy(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 oidcpy(shifted, &sub2);