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Commit | Line | Data |
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68faf689 JH |
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 | ||
10a3fb00 RS |
50 | static void *fill_tree_desc_strict(struct tree_desc *desc, |
51 | const unsigned char *hash) | |
52 | { | |
53 | void *buffer; | |
54 | enum object_type type; | |
55 | unsigned long size; | |
56 | ||
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; | |
64 | } | |
65 | ||
d8febde3 RS |
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 | ||
68faf689 JH |
73 | /* |
74 | * Inspect two trees, and give a score that tells how similar they are. | |
75 | */ | |
76 | static int score_trees(const unsigned char *hash1, const unsigned char *hash2) | |
77 | { | |
78 | struct tree_desc one; | |
79 | struct tree_desc two; | |
10a3fb00 RS |
80 | void *one_buf = fill_tree_desc_strict(&one, hash1); |
81 | void *two_buf = fill_tree_desc_strict(&two, hash2); | |
68faf689 | 82 | int score = 0; |
68faf689 | 83 | |
d8febde3 RS |
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); | |
68faf689 JH |
88 | int cmp; |
89 | ||
d8febde3 RS |
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) | |
68faf689 | 93 | /* two lacks this entry */ |
d8febde3 RS |
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) | |
68faf689 | 102 | /* path1 does not appear in two */ |
d8febde3 RS |
103 | score += score_missing(e1.mode, e1.path); |
104 | else if (cmp > 0) | |
68faf689 | 105 | /* path2 does not appear in one */ |
d8febde3 RS |
106 | score += score_missing(e2.mode, e2.path); |
107 | else if (hashcmp(e1.sha1, e2.sha1)) | |
68faf689 | 108 | /* they are different */ |
d8febde3 | 109 | score += score_differs(e1.mode, e2.mode, e1.path); |
68faf689 JH |
110 | else |
111 | /* same subtree or blob */ | |
d8febde3 | 112 | score += score_matches(e1.mode, e2.mode, e1.path); |
68faf689 JH |
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 unsigned char *hash1, | |
123 | const unsigned char *hash2, | |
124 | int *best_score, | |
125 | char **best_match, | |
538dfe73 | 126 | const char *base, |
68faf689 JH |
127 | int recurse_limit) |
128 | { | |
129 | struct tree_desc one; | |
10a3fb00 | 130 | void *one_buf = fill_tree_desc_strict(&one, hash1); |
68faf689 JH |
131 | |
132 | while (one.size) { | |
133 | const char *path; | |
134 | const unsigned char *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 | 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; | |
149 | } | |
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); | |
157 | } | |
158 | ||
159 | next: | |
160 | update_tree_entry(&one); | |
161 | } | |
162 | free(one_buf); | |
163 | } | |
164 | ||
165 | /* | |
166 | * A tree "hash1" has a subdirectory at "prefix". Come up with a | |
167 | * tree object by replacing it with another tree "hash2". | |
168 | */ | |
169 | static int splice_tree(const unsigned char *hash1, | |
85e51b78 | 170 | const char *prefix, |
68faf689 JH |
171 | const unsigned char *hash2, |
172 | unsigned char *result) | |
173 | { | |
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; | |
184 | ||
185 | subpath = strchr(prefix, '/'); | |
186 | if (!subpath) | |
187 | toplen = strlen(prefix); | |
188 | else { | |
189 | toplen = subpath - prefix; | |
190 | subpath++; | |
191 | } | |
192 | ||
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); | |
197 | ||
198 | rewrite_here = NULL; | |
199 | while (desc.size) { | |
200 | const char *name; | |
201 | unsigned mode; | |
202 | const unsigned char *sha1; | |
203 | ||
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; | |
212 | } | |
213 | update_tree_entry(&desc); | |
214 | } | |
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; | |
223 | } | |
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; | |
230 | } | |
231 | ||
232 | /* | |
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. | |
239 | */ | |
240 | void shift_tree(const unsigned char *hash1, | |
241 | const unsigned char *hash2, | |
242 | unsigned char *shifted, | |
243 | int depth_limit) | |
244 | { | |
245 | char *add_prefix; | |
246 | char *del_prefix; | |
247 | int add_score, del_score; | |
248 | ||
85e51b78 JH |
249 | /* |
250 | * NEEDSWORK: this limits the recursion depth to hardcoded | |
251 | * value '2' to avoid excessive overhead. | |
252 | */ | |
253 | if (!depth_limit) | |
254 | depth_limit = 2; | |
255 | ||
68faf689 JH |
256 | add_score = del_score = score_trees(hash1, hash2); |
257 | add_prefix = xcalloc(1, 1); | |
258 | del_prefix = xcalloc(1, 1); | |
259 | ||
260 | /* | |
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. | |
263 | */ | |
264 | match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit); | |
265 | ||
266 | /* | |
267 | * See if two's subtree resembles one; if so we need to | |
268 | * pick only subtree of two. | |
269 | */ | |
270 | match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit); | |
271 | ||
272 | /* Assume we do not have to do any shifting */ | |
273 | hashcpy(shifted, hash2); | |
274 | ||
275 | if (add_score < del_score) { | |
276 | /* We need to pick a subtree of two */ | |
277 | unsigned mode; | |
278 | ||
279 | if (!*del_prefix) | |
280 | return; | |
281 | ||
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; | |
286 | } | |
287 | ||
288 | if (!*add_prefix) | |
289 | return; | |
290 | ||
291 | splice_tree(hash1, add_prefix, hash2, shifted); | |
292 | } | |
85e51b78 JH |
293 | |
294 | /* | |
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. | |
298 | */ | |
299 | void shift_tree_by(const unsigned char *hash1, | |
300 | const unsigned char *hash2, | |
301 | unsigned char *shifted, | |
302 | const char *shift_prefix) | |
303 | { | |
304 | unsigned char sub1[20], sub2[20]; | |
305 | unsigned mode1, mode2; | |
306 | unsigned candidate = 0; | |
307 | ||
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; | |
312 | ||
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; | |
317 | ||
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; | |
322 | ||
323 | candidate = 0; | |
324 | score = score_trees(sub1, hash2); | |
325 | if (score > best_score) { | |
326 | candidate = 1; | |
327 | best_score = score; | |
328 | } | |
329 | score = score_trees(sub2, hash1); | |
330 | if (score > best_score) | |
331 | candidate = 2; | |
332 | } | |
333 | ||
334 | if (!candidate) { | |
335 | /* Neither is plausible -- do not shift */ | |
336 | hashcpy(shifted, hash2); | |
337 | return; | |
338 | } | |
339 | ||
340 | if (candidate == 1) | |
341 | /* | |
342 | * shift tree2 down by adding shift_prefix above it | |
343 | * to match tree1. | |
344 | */ | |
345 | splice_tree(hash1, shift_prefix, hash2, shifted); | |
346 | else | |
347 | /* | |
348 | * shift tree2 up by removing shift_prefix from it | |
349 | * to match tree1. | |
350 | */ | |
351 | hashcpy(shifted, sub2); | |
352 | } |