Merge branch 'maint-1.8.2' into maint
[git/git.git] / match-trees.c
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1#include "cache.h"
2#include "tree.h"
3#include "tree-walk.h"
4
5static 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
18static 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
31static 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
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50static int base_name_entries_compare(const struct name_entry *a,
51 const struct name_entry *b)
52{
53 return base_name_compare(a->path, tree_entry_len(a), a->mode,
54 b->path, tree_entry_len(b), b->mode);
55}
56
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57/*
58 * Inspect two trees, and give a score that tells how similar they are.
59 */
60static int score_trees(const unsigned char *hash1, const unsigned char *hash2)
61{
62 struct tree_desc one;
63 struct tree_desc two;
64 void *one_buf, *two_buf;
65 int score = 0;
66 enum object_type type;
67 unsigned long size;
68
69 one_buf = read_sha1_file(hash1, &type, &size);
70 if (!one_buf)
71 die("unable to read tree (%s)", sha1_to_hex(hash1));
72 if (type != OBJ_TREE)
73 die("%s is not a tree", sha1_to_hex(hash1));
74 init_tree_desc(&one, one_buf, size);
75 two_buf = read_sha1_file(hash2, &type, &size);
76 if (!two_buf)
77 die("unable to read tree (%s)", sha1_to_hex(hash2));
78 if (type != OBJ_TREE)
79 die("%s is not a tree", sha1_to_hex(hash2));
80 init_tree_desc(&two, two_buf, size);
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81 for (;;) {
82 struct name_entry e1, e2;
83 int got_entry_from_one = tree_entry(&one, &e1);
84 int got_entry_from_two = tree_entry(&two, &e2);
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85 int cmp;
86
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87 if (got_entry_from_one && got_entry_from_two)
88 cmp = base_name_entries_compare(&e1, &e2);
89 else if (got_entry_from_one)
68faf689 90 /* two lacks this entry */
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91 cmp = -1;
92 else if (got_entry_from_two)
93 /* two has more entries */
94 cmp = 1;
95 else
96 break;
97
98 if (cmp < 0)
68faf689 99 /* path1 does not appear in two */
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100 score += score_missing(e1.mode, e1.path);
101 else if (cmp > 0)
68faf689 102 /* path2 does not appear in one */
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103 score += score_missing(e2.mode, e2.path);
104 else if (hashcmp(e1.sha1, e2.sha1))
68faf689 105 /* they are different */
d8febde3 106 score += score_differs(e1.mode, e2.mode, e1.path);
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107 else
108 /* same subtree or blob */
d8febde3 109 score += score_matches(e1.mode, e2.mode, e1.path);
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110 }
111 free(one_buf);
112 free(two_buf);
113 return score;
114}
115
116/*
117 * Match one itself and its subtrees with two and pick the best match.
118 */
119static void match_trees(const unsigned char *hash1,
120 const unsigned char *hash2,
121 int *best_score,
122 char **best_match,
538dfe73 123 const char *base,
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124 int recurse_limit)
125{
126 struct tree_desc one;
127 void *one_buf;
128 enum object_type type;
129 unsigned long size;
130
131 one_buf = read_sha1_file(hash1, &type, &size);
132 if (!one_buf)
133 die("unable to read tree (%s)", sha1_to_hex(hash1));
134 if (type != OBJ_TREE)
135 die("%s is not a tree", sha1_to_hex(hash1));
136 init_tree_desc(&one, one_buf, size);
137
138 while (one.size) {
139 const char *path;
140 const unsigned char *elem;
141 unsigned mode;
142 int score;
143
144 elem = tree_entry_extract(&one, &path, &mode);
145 if (!S_ISDIR(mode))
146 goto next;
147 score = score_trees(elem, hash2);
148 if (*best_score < score) {
149 char *newpath;
150 newpath = xmalloc(strlen(base) + strlen(path) + 1);
151 sprintf(newpath, "%s%s", base, path);
152 free(*best_match);
153 *best_match = newpath;
154 *best_score = score;
155 }
156 if (recurse_limit) {
157 char *newbase;
158 newbase = xmalloc(strlen(base) + strlen(path) + 2);
159 sprintf(newbase, "%s%s/", base, path);
160 match_trees(elem, hash2, best_score, best_match,
161 newbase, recurse_limit - 1);
162 free(newbase);
163 }
164
165 next:
166 update_tree_entry(&one);
167 }
168 free(one_buf);
169}
170
171/*
172 * A tree "hash1" has a subdirectory at "prefix". Come up with a
173 * tree object by replacing it with another tree "hash2".
174 */
175static int splice_tree(const unsigned char *hash1,
85e51b78 176 const char *prefix,
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177 const unsigned char *hash2,
178 unsigned char *result)
179{
180 char *subpath;
181 int toplen;
182 char *buf;
183 unsigned long sz;
184 struct tree_desc desc;
185 unsigned char *rewrite_here;
186 const unsigned char *rewrite_with;
187 unsigned char subtree[20];
188 enum object_type type;
189 int status;
190
191 subpath = strchr(prefix, '/');
192 if (!subpath)
193 toplen = strlen(prefix);
194 else {
195 toplen = subpath - prefix;
196 subpath++;
197 }
198
199 buf = read_sha1_file(hash1, &type, &sz);
200 if (!buf)
201 die("cannot read tree %s", sha1_to_hex(hash1));
202 init_tree_desc(&desc, buf, sz);
203
204 rewrite_here = NULL;
205 while (desc.size) {
206 const char *name;
207 unsigned mode;
208 const unsigned char *sha1;
209
210 sha1 = tree_entry_extract(&desc, &name, &mode);
211 if (strlen(name) == toplen &&
212 !memcmp(name, prefix, toplen)) {
213 if (!S_ISDIR(mode))
214 die("entry %s in tree %s is not a tree",
215 name, sha1_to_hex(hash1));
216 rewrite_here = (unsigned char *) sha1;
217 break;
218 }
219 update_tree_entry(&desc);
220 }
221 if (!rewrite_here)
222 die("entry %.*s not found in tree %s",
223 toplen, prefix, sha1_to_hex(hash1));
224 if (subpath) {
225 status = splice_tree(rewrite_here, subpath, hash2, subtree);
226 if (status)
227 return status;
228 rewrite_with = subtree;
229 }
230 else
231 rewrite_with = hash2;
232 hashcpy(rewrite_here, rewrite_with);
233 status = write_sha1_file(buf, sz, tree_type, result);
234 free(buf);
235 return status;
236}
237
238/*
239 * We are trying to come up with a merge between one and two that
240 * results in a tree shape similar to one. The tree two might
241 * correspond to a subtree of one, in which case it needs to be
242 * shifted down by prefixing otherwise empty directories. On the
243 * other hand, it could cover tree one and we might need to pick a
244 * subtree of it.
245 */
246void shift_tree(const unsigned char *hash1,
247 const unsigned char *hash2,
248 unsigned char *shifted,
249 int depth_limit)
250{
251 char *add_prefix;
252 char *del_prefix;
253 int add_score, del_score;
254
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255 /*
256 * NEEDSWORK: this limits the recursion depth to hardcoded
257 * value '2' to avoid excessive overhead.
258 */
259 if (!depth_limit)
260 depth_limit = 2;
261
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262 add_score = del_score = score_trees(hash1, hash2);
263 add_prefix = xcalloc(1, 1);
264 del_prefix = xcalloc(1, 1);
265
266 /*
267 * See if one's subtree resembles two; if so we need to prefix
268 * two with a few fake trees to match the prefix.
269 */
270 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
271
272 /*
273 * See if two's subtree resembles one; if so we need to
274 * pick only subtree of two.
275 */
276 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
277
278 /* Assume we do not have to do any shifting */
279 hashcpy(shifted, hash2);
280
281 if (add_score < del_score) {
282 /* We need to pick a subtree of two */
283 unsigned mode;
284
285 if (!*del_prefix)
286 return;
287
288 if (get_tree_entry(hash2, del_prefix, shifted, &mode))
289 die("cannot find path %s in tree %s",
290 del_prefix, sha1_to_hex(hash2));
291 return;
292 }
293
294 if (!*add_prefix)
295 return;
296
297 splice_tree(hash1, add_prefix, hash2, shifted);
298}
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299
300/*
301 * The user says the trees will be shifted by this much.
302 * Unfortunately we cannot fundamentally tell which one to
303 * be prefixed, as recursive merge can work in either direction.
304 */
305void shift_tree_by(const unsigned char *hash1,
306 const unsigned char *hash2,
307 unsigned char *shifted,
308 const char *shift_prefix)
309{
310 unsigned char sub1[20], sub2[20];
311 unsigned mode1, mode2;
312 unsigned candidate = 0;
313
314 /* Can hash2 be a tree at shift_prefix in tree hash1? */
315 if (!get_tree_entry(hash1, shift_prefix, sub1, &mode1) &&
316 S_ISDIR(mode1))
317 candidate |= 1;
318
319 /* Can hash1 be a tree at shift_prefix in tree hash2? */
320 if (!get_tree_entry(hash2, shift_prefix, sub2, &mode2) &&
321 S_ISDIR(mode2))
322 candidate |= 2;
323
324 if (candidate == 3) {
325 /* Both are plausible -- we need to evaluate the score */
326 int best_score = score_trees(hash1, hash2);
327 int score;
328
329 candidate = 0;
330 score = score_trees(sub1, hash2);
331 if (score > best_score) {
332 candidate = 1;
333 best_score = score;
334 }
335 score = score_trees(sub2, hash1);
336 if (score > best_score)
337 candidate = 2;
338 }
339
340 if (!candidate) {
341 /* Neither is plausible -- do not shift */
342 hashcpy(shifted, hash2);
343 return;
344 }
345
346 if (candidate == 1)
347 /*
348 * shift tree2 down by adding shift_prefix above it
349 * to match tree1.
350 */
351 splice_tree(hash1, shift_prefix, hash2, shifted);
352 else
353 /*
354 * shift tree2 up by removing shift_prefix from it
355 * to match tree1.
356 */
357 hashcpy(shifted, sub2);
358}