tree-walk: convert tree entry functions to object_id
[git/git.git] / match-trees.c
1 #include "cache.h"
2 #include "tree.h"
3 #include "tree-walk.h"
4
5 static int score_missing(unsigned mode, const char *path)
6 {
7 int score;
8
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;
16 }
17
18 static int score_differs(unsigned mode1, unsigned mode2, const char *path)
19 {
20 int score;
21
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;
29 }
30
31 static int score_matches(unsigned mode1, unsigned mode2, const char *path)
32 {
33 int score;
34
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;
40
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;
48 }
49
50 static void *fill_tree_desc_strict(struct tree_desc *desc,
51 const struct object_id *hash)
52 {
53 void *buffer;
54 enum object_type type;
55 unsigned long size;
56
57 buffer = read_sha1_file(hash->hash, &type, &size);
58 if (!buffer)
59 die("unable to read tree (%s)", oid_to_hex(hash));
60 if (type != OBJ_TREE)
61 die("%s is not a tree", oid_to_hex(hash));
62 init_tree_desc(desc, buffer, size);
63 return buffer;
64 }
65
66 static int base_name_entries_compare(const struct name_entry *a,
67 const struct name_entry *b)
68 {
69 return base_name_compare(a->path, tree_entry_len(a), a->mode,
70 b->path, tree_entry_len(b), b->mode);
71 }
72
73 /*
74 * Inspect two trees, and give a score that tells how similar they are.
75 */
76 static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
77 {
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;
83
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;
89
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;
100
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 (oidcmp(e1.oid, e2.oid))
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);
113 }
114 free(one_buf);
115 free(two_buf);
116 return score;
117 }
118
119 /*
120 * Match one itself and its subtrees with two and pick the best match.
121 */
122 static void match_trees(const struct object_id *hash1,
123 const struct object_id *hash2,
124 int *best_score,
125 char **best_match,
126 const char *base,
127 int recurse_limit)
128 {
129 struct tree_desc one;
130 void *one_buf = fill_tree_desc_strict(&one, hash1);
131
132 while (one.size) {
133 const char *path;
134 const struct object_id *elem;
135 unsigned mode;
136 int score;
137
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 free(*best_match);
144 *best_match = xstrfmt("%s%s", base, path);
145 *best_score = score;
146 }
147 if (recurse_limit) {
148 char *newbase = xstrfmt("%s%s/", base, path);
149 match_trees(elem, hash2, best_score, best_match,
150 newbase, recurse_limit - 1);
151 free(newbase);
152 }
153
154 next:
155 update_tree_entry(&one);
156 }
157 free(one_buf);
158 }
159
160 /*
161 * A tree "oid1" has a subdirectory at "prefix". Come up with a tree object by
162 * replacing it with another tree "oid2".
163 */
164 static int splice_tree(const struct object_id *oid1, const char *prefix,
165 const struct object_id *oid2, struct object_id *result)
166 {
167 char *subpath;
168 int toplen;
169 char *buf;
170 unsigned long sz;
171 struct tree_desc desc;
172 struct object_id *rewrite_here;
173 const struct object_id *rewrite_with;
174 struct object_id subtree;
175 enum object_type type;
176 int status;
177
178 subpath = strchrnul(prefix, '/');
179 toplen = subpath - prefix;
180 if (*subpath)
181 subpath++;
182
183 buf = read_sha1_file(oid1->hash, &type, &sz);
184 if (!buf)
185 die("cannot read tree %s", oid_to_hex(oid1));
186 init_tree_desc(&desc, buf, sz);
187
188 rewrite_here = NULL;
189 while (desc.size) {
190 const char *name;
191 unsigned mode;
192 const struct object_id *oid;
193
194 oid = tree_entry_extract(&desc, &name, &mode);
195 if (strlen(name) == toplen &&
196 !memcmp(name, prefix, toplen)) {
197 if (!S_ISDIR(mode))
198 die("entry %s in tree %s is not a tree", name,
199 oid_to_hex(oid1));
200 rewrite_here = (struct object_id *)oid;
201 break;
202 }
203 update_tree_entry(&desc);
204 }
205 if (!rewrite_here)
206 die("entry %.*s not found in tree %s", toplen, prefix,
207 oid_to_hex(oid1));
208 if (*subpath) {
209 status = splice_tree(rewrite_here, subpath, oid2, &subtree);
210 if (status)
211 return status;
212 rewrite_with = &subtree;
213 } else {
214 rewrite_with = oid2;
215 }
216 oidcpy(rewrite_here, rewrite_with);
217 status = write_object_file(buf, sz, tree_type, result);
218 free(buf);
219 return status;
220 }
221
222 /*
223 * We are trying to come up with a merge between one and two that
224 * results in a tree shape similar to one. The tree two might
225 * correspond to a subtree of one, in which case it needs to be
226 * shifted down by prefixing otherwise empty directories. On the
227 * other hand, it could cover tree one and we might need to pick a
228 * subtree of it.
229 */
230 void shift_tree(const struct object_id *hash1,
231 const struct object_id *hash2,
232 struct object_id *shifted,
233 int depth_limit)
234 {
235 char *add_prefix;
236 char *del_prefix;
237 int add_score, del_score;
238
239 /*
240 * NEEDSWORK: this limits the recursion depth to hardcoded
241 * value '2' to avoid excessive overhead.
242 */
243 if (!depth_limit)
244 depth_limit = 2;
245
246 add_score = del_score = score_trees(hash1, hash2);
247 add_prefix = xcalloc(1, 1);
248 del_prefix = xcalloc(1, 1);
249
250 /*
251 * See if one's subtree resembles two; if so we need to prefix
252 * two with a few fake trees to match the prefix.
253 */
254 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
255
256 /*
257 * See if two's subtree resembles one; if so we need to
258 * pick only subtree of two.
259 */
260 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
261
262 /* Assume we do not have to do any shifting */
263 oidcpy(shifted, hash2);
264
265 if (add_score < del_score) {
266 /* We need to pick a subtree of two */
267 unsigned mode;
268
269 if (!*del_prefix)
270 return;
271
272 if (get_tree_entry(hash2, del_prefix, shifted, &mode))
273 die("cannot find path %s in tree %s",
274 del_prefix, oid_to_hex(hash2));
275 return;
276 }
277
278 if (!*add_prefix)
279 return;
280
281 splice_tree(hash1, add_prefix, hash2, shifted);
282 }
283
284 /*
285 * The user says the trees will be shifted by this much.
286 * Unfortunately we cannot fundamentally tell which one to
287 * be prefixed, as recursive merge can work in either direction.
288 */
289 void shift_tree_by(const struct object_id *hash1,
290 const struct object_id *hash2,
291 struct object_id *shifted,
292 const char *shift_prefix)
293 {
294 struct object_id sub1, sub2;
295 unsigned mode1, mode2;
296 unsigned candidate = 0;
297
298 /* Can hash2 be a tree at shift_prefix in tree hash1? */
299 if (!get_tree_entry(hash1, shift_prefix, &sub1, &mode1) &&
300 S_ISDIR(mode1))
301 candidate |= 1;
302
303 /* Can hash1 be a tree at shift_prefix in tree hash2? */
304 if (!get_tree_entry(hash2, shift_prefix, &sub2, &mode2) &&
305 S_ISDIR(mode2))
306 candidate |= 2;
307
308 if (candidate == 3) {
309 /* Both are plausible -- we need to evaluate the score */
310 int best_score = score_trees(hash1, hash2);
311 int score;
312
313 candidate = 0;
314 score = score_trees(&sub1, hash2);
315 if (score > best_score) {
316 candidate = 1;
317 best_score = score;
318 }
319 score = score_trees(&sub2, hash1);
320 if (score > best_score)
321 candidate = 2;
322 }
323
324 if (!candidate) {
325 /* Neither is plausible -- do not shift */
326 oidcpy(shifted, hash2);
327 return;
328 }
329
330 if (candidate == 1)
331 /*
332 * shift tree2 down by adding shift_prefix above it
333 * to match tree1.
334 */
335 splice_tree(hash1, shift_prefix, hash2, shifted);
336 else
337 /*
338 * shift tree2 up by removing shift_prefix from it
339 * to match tree1.
340 */
341 oidcpy(shifted, &sub2);
342 }