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[git/git.git] / match-trees.c
CommitLineData
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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
10a3fb00 50static void *fill_tree_desc_strict(struct tree_desc *desc,
b6aec868 51 const struct object_id *hash)
10a3fb00
RS
52{
53 void *buffer;
54 enum object_type type;
55 unsigned long size;
56
b6aec868 57 buffer = read_sha1_file(hash->hash, &type, &size);
10a3fb00 58 if (!buffer)
b6aec868 59 die("unable to read tree (%s)", oid_to_hex(hash));
10a3fb00 60 if (type != OBJ_TREE)
b6aec868 61 die("%s is not a tree", oid_to_hex(hash));
10a3fb00
RS
62 init_tree_desc(desc, buffer, size);
63 return buffer;
64}
65
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66static 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
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73/*
74 * Inspect two trees, and give a score that tells how similar they are.
75 */
b6aec868 76static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
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77{
78 struct tree_desc one;
79 struct tree_desc two;
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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
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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);
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88 int cmp;
89
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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 */
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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 */
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103 score += score_missing(e1.mode, e1.path);
104 else if (cmp > 0)
68faf689 105 /* path2 does not appear in one */
d8febde3 106 score += score_missing(e2.mode, e2.path);
7d924c91 107 else if (oidcmp(e1.oid, e2.oid))
68faf689 108 /* they are different */
d8febde3 109 score += score_differs(e1.mode, e2.mode, e1.path);
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110 else
111 /* same subtree or blob */
d8febde3 112 score += score_matches(e1.mode, e2.mode, e1.path);
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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 */
b6aec868 122static void match_trees(const struct object_id *hash1,
123 const struct object_id *hash2,
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124 int *best_score,
125 char **best_match,
538dfe73 126 const char *base,
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127 int recurse_limit)
128{
129 struct tree_desc one;
10a3fb00 130 void *one_buf = fill_tree_desc_strict(&one, hash1);
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131
132 while (one.size) {
133 const char *path;
ce6663a9 134 const struct object_id *elem;
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135 unsigned mode;
136 int score;
137
138 elem = tree_entry_extract(&one, &path, &mode);
139 if (!S_ISDIR(mode))
140 goto next;
b6aec868 141 score = score_trees(elem, hash2);
68faf689 142 if (*best_score < score) {
68faf689 143 free(*best_match);
28310186 144 *best_match = xstrfmt("%s%s", base, path);
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145 *best_score = score;
146 }
147 if (recurse_limit) {
28310186 148 char *newbase = xstrfmt("%s%s/", base, path);
b6aec868 149 match_trees(elem, hash2, best_score, best_match,
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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 "hash1" has a subdirectory at "prefix". Come up with a
162 * tree object by replacing it with another tree "hash2".
163 */
164static int splice_tree(const unsigned char *hash1,
85e51b78 165 const char *prefix,
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166 const unsigned char *hash2,
167 unsigned char *result)
168{
169 char *subpath;
170 int toplen;
171 char *buf;
172 unsigned long sz;
173 struct tree_desc desc;
174 unsigned char *rewrite_here;
175 const unsigned char *rewrite_with;
176 unsigned char subtree[20];
177 enum object_type type;
178 int status;
179
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180 subpath = strchrnul(prefix, '/');
181 toplen = subpath - prefix;
182 if (*subpath)
68faf689 183 subpath++;
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184
185 buf = read_sha1_file(hash1, &type, &sz);
186 if (!buf)
187 die("cannot read tree %s", sha1_to_hex(hash1));
188 init_tree_desc(&desc, buf, sz);
189
190 rewrite_here = NULL;
191 while (desc.size) {
192 const char *name;
193 unsigned mode;
ce6663a9 194 const struct object_id *oid;
68faf689 195
ce6663a9 196 oid = tree_entry_extract(&desc, &name, &mode);
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197 if (strlen(name) == toplen &&
198 !memcmp(name, prefix, toplen)) {
199 if (!S_ISDIR(mode))
200 die("entry %s in tree %s is not a tree",
201 name, sha1_to_hex(hash1));
ce6663a9 202 rewrite_here = (unsigned char *) oid->hash;
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203 break;
204 }
205 update_tree_entry(&desc);
206 }
207 if (!rewrite_here)
208 die("entry %.*s not found in tree %s",
209 toplen, prefix, sha1_to_hex(hash1));
2c5495f7 210 if (*subpath) {
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211 status = splice_tree(rewrite_here, subpath, hash2, subtree);
212 if (status)
213 return status;
214 rewrite_with = subtree;
215 }
216 else
217 rewrite_with = hash2;
218 hashcpy(rewrite_here, rewrite_with);
219 status = write_sha1_file(buf, sz, tree_type, result);
220 free(buf);
221 return status;
222}
223
224/*
225 * We are trying to come up with a merge between one and two that
226 * results in a tree shape similar to one. The tree two might
227 * correspond to a subtree of one, in which case it needs to be
228 * shifted down by prefixing otherwise empty directories. On the
229 * other hand, it could cover tree one and we might need to pick a
230 * subtree of it.
231 */
82db3d44 232void shift_tree(const struct object_id *hash1,
233 const struct object_id *hash2,
234 struct object_id *shifted,
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235 int depth_limit)
236{
237 char *add_prefix;
238 char *del_prefix;
239 int add_score, del_score;
240
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241 /*
242 * NEEDSWORK: this limits the recursion depth to hardcoded
243 * value '2' to avoid excessive overhead.
244 */
245 if (!depth_limit)
246 depth_limit = 2;
247
b6aec868 248 add_score = del_score = score_trees(hash1, hash2);
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249 add_prefix = xcalloc(1, 1);
250 del_prefix = xcalloc(1, 1);
251
252 /*
253 * See if one's subtree resembles two; if so we need to prefix
254 * two with a few fake trees to match the prefix.
255 */
b6aec868 256 match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
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257
258 /*
259 * See if two's subtree resembles one; if so we need to
260 * pick only subtree of two.
261 */
b6aec868 262 match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
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263
264 /* Assume we do not have to do any shifting */
82db3d44 265 oidcpy(shifted, hash2);
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266
267 if (add_score < del_score) {
268 /* We need to pick a subtree of two */
269 unsigned mode;
270
271 if (!*del_prefix)
272 return;
273
82db3d44 274 if (get_tree_entry(hash2->hash, del_prefix, shifted->hash, &mode))
68faf689 275 die("cannot find path %s in tree %s",
82db3d44 276 del_prefix, oid_to_hex(hash2));
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277 return;
278 }
279
280 if (!*add_prefix)
281 return;
282
82db3d44 283 splice_tree(hash1->hash, add_prefix, hash2->hash, shifted->hash);
68faf689 284}
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285
286/*
287 * The user says the trees will be shifted by this much.
288 * Unfortunately we cannot fundamentally tell which one to
289 * be prefixed, as recursive merge can work in either direction.
290 */
82db3d44 291void shift_tree_by(const struct object_id *hash1,
292 const struct object_id *hash2,
293 struct object_id *shifted,
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294 const char *shift_prefix)
295{
82db3d44 296 struct object_id sub1, sub2;
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297 unsigned mode1, mode2;
298 unsigned candidate = 0;
299
300 /* Can hash2 be a tree at shift_prefix in tree hash1? */
82db3d44 301 if (!get_tree_entry(hash1->hash, shift_prefix, sub1.hash, &mode1) &&
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302 S_ISDIR(mode1))
303 candidate |= 1;
304
305 /* Can hash1 be a tree at shift_prefix in tree hash2? */
82db3d44 306 if (!get_tree_entry(hash2->hash, shift_prefix, sub2.hash, &mode2) &&
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307 S_ISDIR(mode2))
308 candidate |= 2;
309
310 if (candidate == 3) {
311 /* Both are plausible -- we need to evaluate the score */
b6aec868 312 int best_score = score_trees(hash1, hash2);
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313 int score;
314
315 candidate = 0;
b6aec868 316 score = score_trees(&sub1, hash2);
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317 if (score > best_score) {
318 candidate = 1;
319 best_score = score;
320 }
b6aec868 321 score = score_trees(&sub2, hash1);
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322 if (score > best_score)
323 candidate = 2;
324 }
325
326 if (!candidate) {
327 /* Neither is plausible -- do not shift */
82db3d44 328 oidcpy(shifted, hash2);
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329 return;
330 }
331
332 if (candidate == 1)
333 /*
334 * shift tree2 down by adding shift_prefix above it
335 * to match tree1.
336 */
82db3d44 337 splice_tree(hash1->hash, shift_prefix, hash2->hash, shifted->hash);
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338 else
339 /*
340 * shift tree2 up by removing shift_prefix from it
341 * to match tree1.
342 */
82db3d44 343 oidcpy(shifted, &sub2);
85e51b78 344}