merge-recursive: get rid of virtual_id
[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         unsigned short score;
116         short 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         /* sink the unused ones to the bottom */
227         if (a->dst < 0)
228                 return (0 <= b->dst);
229         else if (b->dst < 0)
230                 return -1;
231
232         if (a->score == b->score)
233                 return b->name_score - a->name_score;
234
235         return b->score - a->score;
236 }
237
238 struct file_similarity {
239         int src_dst, index;
240         struct diff_filespec *filespec;
241         struct file_similarity *next;
242 };
243
244 static int find_identical_files(struct file_similarity *src,
245                                 struct file_similarity *dst)
246 {
247         int renames = 0;
248
249         /*
250          * Walk over all the destinations ...
251          */
252         do {
253                 struct diff_filespec *target = dst->filespec;
254                 struct file_similarity *p, *best;
255                 int i = 100, best_score = -1;
256
257                 /*
258                  * .. to find the best source match
259                  */
260                 best = NULL;
261                 for (p = src; p; p = p->next) {
262                         int score;
263                         struct diff_filespec *source = p->filespec;
264
265                         /* False hash collission? */
266                         if (hashcmp(source->sha1, target->sha1))
267                                 continue;
268                         /* Non-regular files? If so, the modes must match! */
269                         if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
270                                 if (source->mode != target->mode)
271                                         continue;
272                         }
273                         /* Give higher scores to sources that haven't been used already */
274                         score = !source->rename_used;
275                         score += basename_same(source, target);
276                         if (score > best_score) {
277                                 best = p;
278                                 best_score = score;
279                                 if (score == 2)
280                                         break;
281                         }
282
283                         /* Too many identical alternatives? Pick one */
284                         if (!--i)
285                                 break;
286                 }
287                 if (best) {
288                         record_rename_pair(dst->index, best->index, MAX_SCORE);
289                         renames++;
290                 }
291         } while ((dst = dst->next) != NULL);
292         return renames;
293 }
294
295 static void free_similarity_list(struct file_similarity *p)
296 {
297         while (p) {
298                 struct file_similarity *entry = p;
299                 p = p->next;
300                 free(entry);
301         }
302 }
303
304 static int find_same_files(void *ptr)
305 {
306         int ret;
307         struct file_similarity *p = ptr;
308         struct file_similarity *src = NULL, *dst = NULL;
309
310         /* Split the hash list up into sources and destinations */
311         do {
312                 struct file_similarity *entry = p;
313                 p = p->next;
314                 if (entry->src_dst < 0) {
315                         entry->next = src;
316                         src = entry;
317                 } else {
318                         entry->next = dst;
319                         dst = entry;
320                 }
321         } while (p);
322
323         /*
324          * If we have both sources *and* destinations, see if
325          * we can match them up
326          */
327         ret = (src && dst) ? find_identical_files(src, dst) : 0;
328
329         /* Free the hashes and return the number of renames found */
330         free_similarity_list(src);
331         free_similarity_list(dst);
332         return ret;
333 }
334
335 static unsigned int hash_filespec(struct diff_filespec *filespec)
336 {
337         unsigned int hash;
338         if (!filespec->sha1_valid) {
339                 if (diff_populate_filespec(filespec, 0))
340                         return 0;
341                 hash_sha1_file(filespec->data, filespec->size, "blob", filespec->sha1);
342         }
343         memcpy(&hash, filespec->sha1, sizeof(hash));
344         return hash;
345 }
346
347 static void insert_file_table(struct hash_table *table, int src_dst, int index, struct diff_filespec *filespec)
348 {
349         void **pos;
350         unsigned int hash;
351         struct file_similarity *entry = xmalloc(sizeof(*entry));
352
353         entry->src_dst = src_dst;
354         entry->index = index;
355         entry->filespec = filespec;
356         entry->next = NULL;
357
358         hash = hash_filespec(filespec);
359         pos = insert_hash(hash, entry, table);
360
361         /* We already had an entry there? */
362         if (pos) {
363                 entry->next = *pos;
364                 *pos = entry;
365         }
366 }
367
368 /*
369  * Find exact renames first.
370  *
371  * The first round matches up the up-to-date entries,
372  * and then during the second round we try to match
373  * cache-dirty entries as well.
374  */
375 static int find_exact_renames(void)
376 {
377         int i;
378         struct hash_table file_table;
379
380         init_hash(&file_table);
381         for (i = 0; i < rename_src_nr; i++)
382                 insert_file_table(&file_table, -1, i, rename_src[i].one);
383
384         for (i = 0; i < rename_dst_nr; i++)
385                 insert_file_table(&file_table, 1, i, rename_dst[i].two);
386
387         /* Find the renames */
388         i = for_each_hash(&file_table, find_same_files);
389
390         /* .. and free the hash data structure */
391         free_hash(&file_table);
392
393         return i;
394 }
395
396 #define NUM_CANDIDATE_PER_DST 4
397 static void record_if_better(struct diff_score m[], struct diff_score *o)
398 {
399         int i, worst;
400
401         /* find the worst one */
402         worst = 0;
403         for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
404                 if (score_compare(&m[i], &m[worst]) > 0)
405                         worst = i;
406
407         /* is it better than the worst one? */
408         if (score_compare(&m[worst], o) > 0)
409                 m[worst] = *o;
410 }
411
412 void diffcore_rename(struct diff_options *options)
413 {
414         int detect_rename = options->detect_rename;
415         int minimum_score = options->rename_score;
416         int rename_limit = options->rename_limit;
417         struct diff_queue_struct *q = &diff_queued_diff;
418         struct diff_queue_struct outq;
419         struct diff_score *mx;
420         int i, j, rename_count;
421         int num_create, num_src, dst_cnt;
422
423         if (!minimum_score)
424                 minimum_score = DEFAULT_RENAME_SCORE;
425
426         for (i = 0; i < q->nr; i++) {
427                 struct diff_filepair *p = q->queue[i];
428                 if (!DIFF_FILE_VALID(p->one)) {
429                         if (!DIFF_FILE_VALID(p->two))
430                                 continue; /* unmerged */
431                         else if (options->single_follow &&
432                                  strcmp(options->single_follow, p->two->path))
433                                 continue; /* not interested */
434                         else
435                                 locate_rename_dst(p->two, 1);
436                 }
437                 else if (!DIFF_FILE_VALID(p->two)) {
438                         /*
439                          * If the source is a broken "delete", and
440                          * they did not really want to get broken,
441                          * that means the source actually stays.
442                          * So we increment the "rename_used" score
443                          * by one, to indicate ourselves as a user
444                          */
445                         if (p->broken_pair && !p->score)
446                                 p->one->rename_used++;
447                         register_rename_src(p->one, p->score);
448                 }
449                 else if (detect_rename == DIFF_DETECT_COPY) {
450                         /*
451                          * Increment the "rename_used" score by
452                          * one, to indicate ourselves as a user.
453                          */
454                         p->one->rename_used++;
455                         register_rename_src(p->one, p->score);
456                 }
457         }
458         if (rename_dst_nr == 0 || rename_src_nr == 0)
459                 goto cleanup; /* nothing to do */
460
461         /*
462          * We really want to cull the candidates list early
463          * with cheap tests in order to avoid doing deltas.
464          */
465         rename_count = find_exact_renames();
466
467         /* Did we only want exact renames? */
468         if (minimum_score == MAX_SCORE)
469                 goto cleanup;
470
471         /*
472          * Calculate how many renames are left (but all the source
473          * files still remain as options for rename/copies!)
474          */
475         num_create = (rename_dst_nr - rename_count);
476         num_src = rename_src_nr;
477
478         /* All done? */
479         if (!num_create)
480                 goto cleanup;
481
482         /*
483          * This basically does a test for the rename matrix not
484          * growing larger than a "rename_limit" square matrix, ie:
485          *
486          *    num_create * num_src > rename_limit * rename_limit
487          *
488          * but handles the potential overflow case specially (and we
489          * assume at least 32-bit integers)
490          */
491         if (rename_limit <= 0 || rename_limit > 32767)
492                 rename_limit = 32767;
493         if ((num_create > rename_limit && num_src > rename_limit) ||
494             (num_create * num_src > rename_limit * rename_limit)) {
495                 if (options->warn_on_too_large_rename)
496                         warning("too many files, skipping inexact rename detection");
497                 goto cleanup;
498         }
499
500         mx = xcalloc(num_create * NUM_CANDIDATE_PER_DST, sizeof(*mx));
501         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
502                 struct diff_filespec *two = rename_dst[i].two;
503                 struct diff_score *m;
504
505                 if (rename_dst[i].pair)
506                         continue; /* dealt with exact match already. */
507
508                 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
509                 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
510                         m[j].dst = -1;
511
512                 for (j = 0; j < rename_src_nr; j++) {
513                         struct diff_filespec *one = rename_src[j].one;
514                         struct diff_score this_src;
515                         this_src.score = estimate_similarity(one, two,
516                                                              minimum_score);
517                         this_src.name_score = basename_same(one, two);
518                         this_src.dst = i;
519                         this_src.src = j;
520                         record_if_better(m, &this_src);
521                         diff_free_filespec_blob(one);
522                 }
523                 /* We do not need the text anymore */
524                 diff_free_filespec_blob(two);
525                 dst_cnt++;
526         }
527
528         /* cost matrix sorted by most to least similar pair */
529         qsort(mx, dst_cnt * NUM_CANDIDATE_PER_DST, sizeof(*mx), score_compare);
530
531         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
532                 struct diff_rename_dst *dst;
533
534                 if ((mx[i].dst < 0) ||
535                     (mx[i].score < minimum_score))
536                         break; /* there is no more usable pair. */
537                 dst = &rename_dst[mx[i].dst];
538                 if (dst->pair)
539                         continue; /* already done, either exact or fuzzy. */
540                 if (rename_src[mx[i].src].one->rename_used)
541                         continue;
542                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
543                 rename_count++;
544         }
545
546         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
547                 struct diff_rename_dst *dst;
548
549                 if ((mx[i].dst < 0) ||
550                     (mx[i].score < minimum_score))
551                         break; /* there is no more usable pair. */
552                 dst = &rename_dst[mx[i].dst];
553                 if (dst->pair)
554                         continue; /* already done, either exact or fuzzy. */
555                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
556                 rename_count++;
557         }
558         free(mx);
559
560  cleanup:
561         /* At this point, we have found some renames and copies and they
562          * are recorded in rename_dst.  The original list is still in *q.
563          */
564         outq.queue = NULL;
565         outq.nr = outq.alloc = 0;
566         for (i = 0; i < q->nr; i++) {
567                 struct diff_filepair *p = q->queue[i];
568                 struct diff_filepair *pair_to_free = NULL;
569
570                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
571                         /*
572                          * Creation
573                          *
574                          * We would output this create record if it has
575                          * not been turned into a rename/copy already.
576                          */
577                         struct diff_rename_dst *dst =
578                                 locate_rename_dst(p->two, 0);
579                         if (dst && dst->pair) {
580                                 diff_q(&outq, dst->pair);
581                                 pair_to_free = p;
582                         }
583                         else
584                                 /* no matching rename/copy source, so
585                                  * record this as a creation.
586                                  */
587                                 diff_q(&outq, p);
588                 }
589                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
590                         /*
591                          * Deletion
592                          *
593                          * We would output this delete record if:
594                          *
595                          * (1) this is a broken delete and the counterpart
596                          *     broken create remains in the output; or
597                          * (2) this is not a broken delete, and rename_dst
598                          *     does not have a rename/copy to move p->one->path
599                          *     out of existence.
600                          *
601                          * Otherwise, the counterpart broken create
602                          * has been turned into a rename-edit; or
603                          * delete did not have a matching create to
604                          * begin with.
605                          */
606                         if (DIFF_PAIR_BROKEN(p)) {
607                                 /* broken delete */
608                                 struct diff_rename_dst *dst =
609                                         locate_rename_dst(p->one, 0);
610                                 if (dst && dst->pair)
611                                         /* counterpart is now rename/copy */
612                                         pair_to_free = p;
613                         }
614                         else {
615                                 if (p->one->rename_used)
616                                         /* this path remains */
617                                         pair_to_free = p;
618                         }
619
620                         if (pair_to_free)
621                                 ;
622                         else
623                                 diff_q(&outq, p);
624                 }
625                 else if (!diff_unmodified_pair(p))
626                         /* all the usual ones need to be kept */
627                         diff_q(&outq, p);
628                 else
629                         /* no need to keep unmodified pairs */
630                         pair_to_free = p;
631
632                 if (pair_to_free)
633                         diff_free_filepair(pair_to_free);
634         }
635         diff_debug_queue("done copying original", &outq);
636
637         free(q->queue);
638         *q = outq;
639         diff_debug_queue("done collapsing", q);
640
641         for (i = 0; i < rename_dst_nr; i++)
642                 free_filespec(rename_dst[i].two);
643
644         free(rename_dst);
645         rename_dst = NULL;
646         rename_dst_nr = rename_dst_alloc = 0;
647         free(rename_src);
648         rename_src = NULL;
649         rename_src_nr = rename_src_alloc = 0;
650         return;
651 }