Merge branch 'maint'
[git] / diffcore-rename.c
1 /*
2  * Copyright (C) 2005 Junio C Hamano
3  */
4 #include "cache.h"
5 #include "diff.h"
6 #include "diffcore.h"
7 #include "hash.h"
8
9 /* Table of rename/copy destinations */
10
11 static struct diff_rename_dst {
12         struct diff_filespec *two;
13         struct diff_filepair *pair;
14 } *rename_dst;
15 static int rename_dst_nr, rename_dst_alloc;
16
17 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
18                                                  int insert_ok)
19 {
20         int first, last;
21
22         first = 0;
23         last = rename_dst_nr;
24         while (last > first) {
25                 int next = (last + first) >> 1;
26                 struct diff_rename_dst *dst = &(rename_dst[next]);
27                 int cmp = strcmp(two->path, dst->two->path);
28                 if (!cmp)
29                         return dst;
30                 if (cmp < 0) {
31                         last = next;
32                         continue;
33                 }
34                 first = next+1;
35         }
36         /* not found */
37         if (!insert_ok)
38                 return NULL;
39         /* insert to make it at "first" */
40         if (rename_dst_alloc <= rename_dst_nr) {
41                 rename_dst_alloc = alloc_nr(rename_dst_alloc);
42                 rename_dst = xrealloc(rename_dst,
43                                       rename_dst_alloc * sizeof(*rename_dst));
44         }
45         rename_dst_nr++;
46         if (first < rename_dst_nr)
47                 memmove(rename_dst + first + 1, rename_dst + first,
48                         (rename_dst_nr - first - 1) * sizeof(*rename_dst));
49         rename_dst[first].two = alloc_filespec(two->path);
50         fill_filespec(rename_dst[first].two, two->sha1, two->mode);
51         rename_dst[first].pair = NULL;
52         return &(rename_dst[first]);
53 }
54
55 /* Table of rename/copy src files */
56 static struct diff_rename_src {
57         struct diff_filespec *one;
58         unsigned short score; /* to remember the break score */
59 } *rename_src;
60 static int rename_src_nr, rename_src_alloc;
61
62 static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
63                                                    unsigned short score)
64 {
65         int first, last;
66
67         first = 0;
68         last = rename_src_nr;
69         while (last > first) {
70                 int next = (last + first) >> 1;
71                 struct diff_rename_src *src = &(rename_src[next]);
72                 int cmp = strcmp(one->path, src->one->path);
73                 if (!cmp)
74                         return src;
75                 if (cmp < 0) {
76                         last = next;
77                         continue;
78                 }
79                 first = next+1;
80         }
81
82         /* insert to make it at "first" */
83         if (rename_src_alloc <= rename_src_nr) {
84                 rename_src_alloc = alloc_nr(rename_src_alloc);
85                 rename_src = xrealloc(rename_src,
86                                       rename_src_alloc * sizeof(*rename_src));
87         }
88         rename_src_nr++;
89         if (first < rename_src_nr)
90                 memmove(rename_src + first + 1, rename_src + first,
91                         (rename_src_nr - first - 1) * sizeof(*rename_src));
92         rename_src[first].one = one;
93         rename_src[first].score = score;
94         return &(rename_src[first]);
95 }
96
97 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
98 {
99         int src_len = strlen(src->path), dst_len = strlen(dst->path);
100         while (src_len && dst_len) {
101                 char c1 = src->path[--src_len];
102                 char c2 = dst->path[--dst_len];
103                 if (c1 != c2)
104                         return 0;
105                 if (c1 == '/')
106                         return 1;
107         }
108         return (!src_len || src->path[src_len - 1] == '/') &&
109                 (!dst_len || dst->path[dst_len - 1] == '/');
110 }
111
112 struct diff_score {
113         int src; /* index in rename_src */
114         int dst; /* index in rename_dst */
115         int score;
116         int name_score;
117 };
118
119 static int estimate_similarity(struct diff_filespec *src,
120                                struct diff_filespec *dst,
121                                int minimum_score)
122 {
123         /* src points at a file that existed in the original tree (or
124          * optionally a file in the destination tree) and dst points
125          * at a newly created file.  They may be quite similar, in which
126          * case we want to say src is renamed to dst or src is copied into
127          * dst, and then some edit has been applied to dst.
128          *
129          * Compare them and return how similar they are, representing
130          * the score as an integer between 0 and MAX_SCORE.
131          *
132          * When there is an exact match, it is considered a better
133          * match than anything else; the destination does not even
134          * call into this function in that case.
135          */
136         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
137         unsigned long delta_limit;
138         int score;
139
140         /* We deal only with regular files.  Symlink renames are handled
141          * only when they are exact matches --- in other words, no edits
142          * after renaming.
143          */
144         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
145                 return 0;
146
147         /*
148          * Need to check that source and destination sizes are
149          * filled in before comparing them.
150          *
151          * If we already have "cnt_data" filled in, we know it's
152          * all good (avoid checking the size for zero, as that
153          * is a possible size - we really should have a flag to
154          * say whether the size is valid or not!)
155          */
156         if (!src->cnt_data && diff_populate_filespec(src, 0))
157                 return 0;
158         if (!dst->cnt_data && diff_populate_filespec(dst, 0))
159                 return 0;
160
161         max_size = ((src->size > dst->size) ? src->size : dst->size);
162         base_size = ((src->size < dst->size) ? src->size : dst->size);
163         delta_size = max_size - base_size;
164
165         /* We would not consider edits that change the file size so
166          * drastically.  delta_size must be smaller than
167          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
168          *
169          * Note that base_size == 0 case is handled here already
170          * and the final score computation below would not have a
171          * divide-by-zero issue.
172          */
173         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
174                 return 0;
175
176         delta_limit = (unsigned long)
177                 (base_size * (MAX_SCORE-minimum_score) / MAX_SCORE);
178         if (diffcore_count_changes(src, dst,
179                                    &src->cnt_data, &dst->cnt_data,
180                                    delta_limit,
181                                    &src_copied, &literal_added))
182                 return 0;
183
184         /* How similar are they?
185          * what percentage of material in dst are from source?
186          */
187         if (!dst->size)
188                 score = 0; /* should not happen */
189         else
190                 score = (int)(src_copied * MAX_SCORE / max_size);
191         return score;
192 }
193
194 static void record_rename_pair(int dst_index, int src_index, int score)
195 {
196         struct diff_filespec *src, *dst;
197         struct diff_filepair *dp;
198
199         if (rename_dst[dst_index].pair)
200                 die("internal error: dst already matched.");
201
202         src = rename_src[src_index].one;
203         src->rename_used++;
204         src->count++;
205
206         dst = rename_dst[dst_index].two;
207         dst->count++;
208
209         dp = diff_queue(NULL, src, dst);
210         dp->renamed_pair = 1;
211         if (!strcmp(src->path, dst->path))
212                 dp->score = rename_src[src_index].score;
213         else
214                 dp->score = score;
215         rename_dst[dst_index].pair = dp;
216 }
217
218 /*
219  * We sort the rename similarity matrix with the score, in descending
220  * order (the most similar first).
221  */
222 static int score_compare(const void *a_, const void *b_)
223 {
224         const struct diff_score *a = a_, *b = b_;
225
226         if (a->score == b->score)
227                 return b->name_score - a->name_score;
228
229         return b->score - a->score;
230 }
231
232 struct file_similarity {
233         int src_dst, index;
234         struct diff_filespec *filespec;
235         struct file_similarity *next;
236 };
237
238 static int find_identical_files(struct file_similarity *src,
239                                 struct file_similarity *dst)
240 {
241         int renames = 0;
242
243         /*
244          * Walk over all the destinations ...
245          */
246         do {
247                 struct diff_filespec *one = dst->filespec;
248                 struct file_similarity *p, *best;
249                 int i = 100;
250
251                 /*
252                  * .. to find the best source match
253                  */
254                 best = NULL;
255                 for (p = src; p; p = p->next) {
256                         struct diff_filespec *two = p->filespec;
257
258                         /* False hash collission? */
259                         if (hashcmp(one->sha1, two->sha1))
260                                 continue;
261                         /* Non-regular files? If so, the modes must match! */
262                         if (!S_ISREG(one->mode) || !S_ISREG(two->mode)) {
263                                 if (one->mode != two->mode)
264                                         continue;
265                         }
266                         best = p;
267                         if (basename_same(one, two))
268                                 break;
269
270                         /* Too many identical alternatives? Pick one */
271                         if (!--i)
272                                 break;
273                 }
274                 if (best) {
275                         record_rename_pair(dst->index, best->index, MAX_SCORE);
276                         renames++;
277                 }
278         } while ((dst = dst->next) != NULL);
279         return renames;
280 }
281
282 static void free_similarity_list(struct file_similarity *p)
283 {
284         while (p) {
285                 struct file_similarity *entry = p;
286                 p = p->next;
287                 free(entry);
288         }
289 }
290
291 static int find_same_files(void *ptr)
292 {
293         int ret;
294         struct file_similarity *p = ptr;
295         struct file_similarity *src = NULL, *dst = NULL;
296
297         /* Split the hash list up into sources and destinations */
298         do {
299                 struct file_similarity *entry = p;
300                 p = p->next;
301                 if (entry->src_dst < 0) {
302                         entry->next = src;
303                         src = entry;
304                 } else {
305                         entry->next = dst;
306                         dst = entry;
307                 }
308         } while (p);
309
310         /*
311          * If we have both sources *and* destinations, see if
312          * we can match them up
313          */
314         ret = (src && dst) ? find_identical_files(src, dst) : 0;
315
316         /* Free the hashes and return the number of renames found */
317         free_similarity_list(src);
318         free_similarity_list(dst);
319         return ret;
320 }
321
322 static unsigned int hash_filespec(struct diff_filespec *filespec)
323 {
324         unsigned int hash;
325         if (!filespec->sha1_valid) {
326                 if (diff_populate_filespec(filespec, 0))
327                         return 0;
328                 hash_sha1_file(filespec->data, filespec->size, "blob", filespec->sha1);
329         }
330         memcpy(&hash, filespec->sha1, sizeof(hash));
331         return hash;
332 }
333
334 static void insert_file_table(struct hash_table *table, int src_dst, int index, struct diff_filespec *filespec)
335 {
336         void **pos;
337         unsigned int hash;
338         struct file_similarity *entry = xmalloc(sizeof(*entry));
339
340         entry->src_dst = src_dst;
341         entry->index = index;
342         entry->filespec = filespec;
343         entry->next = NULL;
344
345         hash = hash_filespec(filespec);
346         pos = insert_hash(hash, entry, table);
347
348         /* We already had an entry there? */
349         if (pos) {
350                 entry->next = *pos;
351                 *pos = entry;
352         }
353 }
354
355 /*
356  * Find exact renames first.
357  *
358  * The first round matches up the up-to-date entries,
359  * and then during the second round we try to match
360  * cache-dirty entries as well.
361  */
362 static int find_exact_renames(void)
363 {
364         int i;
365         struct hash_table file_table;
366
367         init_hash(&file_table);
368         for (i = 0; i < rename_src_nr; i++)
369                 insert_file_table(&file_table, -1, i, rename_src[i].one);
370
371         for (i = 0; i < rename_dst_nr; i++)
372                 insert_file_table(&file_table, 1, i, rename_dst[i].two);
373
374         /* Find the renames */
375         i = for_each_hash(&file_table, find_same_files);
376
377         /* .. and free the hash data structure */
378         free_hash(&file_table);
379
380         return i;
381 }
382
383 void diffcore_rename(struct diff_options *options)
384 {
385         int detect_rename = options->detect_rename;
386         int minimum_score = options->rename_score;
387         int rename_limit = options->rename_limit;
388         struct diff_queue_struct *q = &diff_queued_diff;
389         struct diff_queue_struct outq;
390         struct diff_score *mx;
391         int i, j, rename_count;
392         int num_create, num_src, dst_cnt;
393
394         if (!minimum_score)
395                 minimum_score = DEFAULT_RENAME_SCORE;
396
397         for (i = 0; i < q->nr; i++) {
398                 struct diff_filepair *p = q->queue[i];
399                 if (!DIFF_FILE_VALID(p->one)) {
400                         if (!DIFF_FILE_VALID(p->two))
401                                 continue; /* unmerged */
402                         else if (options->single_follow &&
403                                  strcmp(options->single_follow, p->two->path))
404                                 continue; /* not interested */
405                         else
406                                 locate_rename_dst(p->two, 1);
407                 }
408                 else if (!DIFF_FILE_VALID(p->two)) {
409                         /*
410                          * If the source is a broken "delete", and
411                          * they did not really want to get broken,
412                          * that means the source actually stays.
413                          * So we increment the "rename_used" score
414                          * by one, to indicate ourselves as a user
415                          */
416                         if (p->broken_pair && !p->score)
417                                 p->one->rename_used++;
418                         register_rename_src(p->one, p->score);
419                 }
420                 else if (detect_rename == DIFF_DETECT_COPY) {
421                         /*
422                          * Increment the "rename_used" score by
423                          * one, to indicate ourselves as a user.
424                          */
425                         p->one->rename_used++;
426                         register_rename_src(p->one, p->score);
427                 }
428         }
429         if (rename_dst_nr == 0 || rename_src_nr == 0)
430                 goto cleanup; /* nothing to do */
431
432         /*
433          * We really want to cull the candidates list early
434          * with cheap tests in order to avoid doing deltas.
435          */
436         rename_count = find_exact_renames();
437
438         /* Did we only want exact renames? */
439         if (minimum_score == MAX_SCORE)
440                 goto cleanup;
441
442         /*
443          * Calculate how many renames are left (but all the source
444          * files still remain as options for rename/copies!)
445          */
446         num_create = (rename_dst_nr - rename_count);
447         num_src = rename_src_nr;
448
449         /* All done? */
450         if (!num_create)
451                 goto cleanup;
452
453         /*
454          * This basically does a test for the rename matrix not
455          * growing larger than a "rename_limit" square matrix, ie:
456          *
457          *    num_create * num_src > rename_limit * rename_limit
458          *
459          * but handles the potential overflow case specially (and we
460          * assume at least 32-bit integers)
461          */
462         if (rename_limit <= 0 || rename_limit > 32767)
463                 rename_limit = 32767;
464         if (num_create > rename_limit && num_src > rename_limit)
465                 goto cleanup;
466         if (num_create * num_src > rename_limit * rename_limit)
467                 goto cleanup;
468
469         mx = xmalloc(sizeof(*mx) * num_create * num_src);
470         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
471                 int base = dst_cnt * num_src;
472                 struct diff_filespec *two = rename_dst[i].two;
473                 if (rename_dst[i].pair)
474                         continue; /* dealt with exact match already. */
475                 for (j = 0; j < rename_src_nr; j++) {
476                         struct diff_filespec *one = rename_src[j].one;
477                         struct diff_score *m = &mx[base+j];
478                         m->src = j;
479                         m->dst = i;
480                         m->score = estimate_similarity(one, two,
481                                                        minimum_score);
482                         m->name_score = basename_same(one, two);
483                         diff_free_filespec_blob(one);
484                 }
485                 /* We do not need the text anymore */
486                 diff_free_filespec_blob(two);
487                 dst_cnt++;
488         }
489         /* cost matrix sorted by most to least similar pair */
490         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
491         for (i = 0; i < num_create * num_src; i++) {
492                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
493                 if (dst->pair)
494                         continue; /* already done, either exact or fuzzy. */
495                 if (mx[i].score < minimum_score)
496                         break; /* there is no more usable pair. */
497                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
498                 rename_count++;
499         }
500         free(mx);
501
502  cleanup:
503         /* At this point, we have found some renames and copies and they
504          * are recorded in rename_dst.  The original list is still in *q.
505          */
506         outq.queue = NULL;
507         outq.nr = outq.alloc = 0;
508         for (i = 0; i < q->nr; i++) {
509                 struct diff_filepair *p = q->queue[i];
510                 struct diff_filepair *pair_to_free = NULL;
511
512                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
513                         /*
514                          * Creation
515                          *
516                          * We would output this create record if it has
517                          * not been turned into a rename/copy already.
518                          */
519                         struct diff_rename_dst *dst =
520                                 locate_rename_dst(p->two, 0);
521                         if (dst && dst->pair) {
522                                 diff_q(&outq, dst->pair);
523                                 pair_to_free = p;
524                         }
525                         else
526                                 /* no matching rename/copy source, so
527                                  * record this as a creation.
528                                  */
529                                 diff_q(&outq, p);
530                 }
531                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
532                         /*
533                          * Deletion
534                          *
535                          * We would output this delete record if:
536                          *
537                          * (1) this is a broken delete and the counterpart
538                          *     broken create remains in the output; or
539                          * (2) this is not a broken delete, and rename_dst
540                          *     does not have a rename/copy to move p->one->path
541                          *     out of existence.
542                          *
543                          * Otherwise, the counterpart broken create
544                          * has been turned into a rename-edit; or
545                          * delete did not have a matching create to
546                          * begin with.
547                          */
548                         if (DIFF_PAIR_BROKEN(p)) {
549                                 /* broken delete */
550                                 struct diff_rename_dst *dst =
551                                         locate_rename_dst(p->one, 0);
552                                 if (dst && dst->pair)
553                                         /* counterpart is now rename/copy */
554                                         pair_to_free = p;
555                         }
556                         else {
557                                 if (p->one->rename_used)
558                                         /* this path remains */
559                                         pair_to_free = p;
560                         }
561
562                         if (pair_to_free)
563                                 ;
564                         else
565                                 diff_q(&outq, p);
566                 }
567                 else if (!diff_unmodified_pair(p))
568                         /* all the usual ones need to be kept */
569                         diff_q(&outq, p);
570                 else
571                         /* no need to keep unmodified pairs */
572                         pair_to_free = p;
573
574                 if (pair_to_free)
575                         diff_free_filepair(pair_to_free);
576         }
577         diff_debug_queue("done copying original", &outq);
578
579         free(q->queue);
580         *q = outq;
581         diff_debug_queue("done collapsing", q);
582
583         for (i = 0; i < rename_dst_nr; i++)
584                 free_filespec(rename_dst[i].two);
585
586         free(rename_dst);
587         rename_dst = NULL;
588         rename_dst_nr = rename_dst_alloc = 0;
589         free(rename_src);
590         rename_src = NULL;
591         rename_src_nr = rename_src_alloc = 0;
592         return;
593 }