Merge branch 'ew/http-backend-batch-headers'
[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 "hashmap.h"
8 #include "progress.h"
9
10 /* Table of rename/copy destinations */
11
12 static struct diff_rename_dst {
13         struct diff_filespec *two;
14         struct diff_filepair *pair;
15 } *rename_dst;
16 static int rename_dst_nr, rename_dst_alloc;
17
18 static int find_rename_dst(struct diff_filespec *two)
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 next;
30                 if (cmp < 0) {
31                         last = next;
32                         continue;
33                 }
34                 first = next+1;
35         }
36         return -first - 1;
37 }
38
39 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two)
40 {
41         int ofs = find_rename_dst(two);
42         return ofs < 0 ? NULL : &rename_dst[ofs];
43 }
44
45 /*
46  * Returns 0 on success, -1 if we found a duplicate.
47  */
48 static int add_rename_dst(struct diff_filespec *two)
49 {
50         int first = find_rename_dst(two);
51
52         if (first >= 0)
53                 return -1;
54         first = -first - 1;
55
56         /* insert to make it at "first" */
57         ALLOC_GROW(rename_dst, rename_dst_nr + 1, rename_dst_alloc);
58         rename_dst_nr++;
59         if (first < rename_dst_nr)
60                 memmove(rename_dst + first + 1, rename_dst + first,
61                         (rename_dst_nr - first - 1) * sizeof(*rename_dst));
62         rename_dst[first].two = alloc_filespec(two->path);
63         fill_filespec(rename_dst[first].two, two->oid.hash, two->oid_valid,
64                       two->mode);
65         rename_dst[first].pair = NULL;
66         return 0;
67 }
68
69 /* Table of rename/copy src files */
70 static struct diff_rename_src {
71         struct diff_filepair *p;
72         unsigned short score; /* to remember the break score */
73 } *rename_src;
74 static int rename_src_nr, rename_src_alloc;
75
76 static struct diff_rename_src *register_rename_src(struct diff_filepair *p)
77 {
78         int first, last;
79         struct diff_filespec *one = p->one;
80         unsigned short score = p->score;
81
82         first = 0;
83         last = rename_src_nr;
84         while (last > first) {
85                 int next = (last + first) >> 1;
86                 struct diff_rename_src *src = &(rename_src[next]);
87                 int cmp = strcmp(one->path, src->p->one->path);
88                 if (!cmp)
89                         return src;
90                 if (cmp < 0) {
91                         last = next;
92                         continue;
93                 }
94                 first = next+1;
95         }
96
97         /* insert to make it at "first" */
98         ALLOC_GROW(rename_src, rename_src_nr + 1, rename_src_alloc);
99         rename_src_nr++;
100         if (first < rename_src_nr)
101                 memmove(rename_src + first + 1, rename_src + first,
102                         (rename_src_nr - first - 1) * sizeof(*rename_src));
103         rename_src[first].p = p;
104         rename_src[first].score = score;
105         return &(rename_src[first]);
106 }
107
108 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
109 {
110         int src_len = strlen(src->path), dst_len = strlen(dst->path);
111         while (src_len && dst_len) {
112                 char c1 = src->path[--src_len];
113                 char c2 = dst->path[--dst_len];
114                 if (c1 != c2)
115                         return 0;
116                 if (c1 == '/')
117                         return 1;
118         }
119         return (!src_len || src->path[src_len - 1] == '/') &&
120                 (!dst_len || dst->path[dst_len - 1] == '/');
121 }
122
123 struct diff_score {
124         int src; /* index in rename_src */
125         int dst; /* index in rename_dst */
126         unsigned short score;
127         short name_score;
128 };
129
130 static int estimate_similarity(struct diff_filespec *src,
131                                struct diff_filespec *dst,
132                                int minimum_score)
133 {
134         /* src points at a file that existed in the original tree (or
135          * optionally a file in the destination tree) and dst points
136          * at a newly created file.  They may be quite similar, in which
137          * case we want to say src is renamed to dst or src is copied into
138          * dst, and then some edit has been applied to dst.
139          *
140          * Compare them and return how similar they are, representing
141          * the score as an integer between 0 and MAX_SCORE.
142          *
143          * When there is an exact match, it is considered a better
144          * match than anything else; the destination does not even
145          * call into this function in that case.
146          */
147         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
148         unsigned long delta_limit;
149         int score;
150
151         /* We deal only with regular files.  Symlink renames are handled
152          * only when they are exact matches --- in other words, no edits
153          * after renaming.
154          */
155         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
156                 return 0;
157
158         /*
159          * Need to check that source and destination sizes are
160          * filled in before comparing them.
161          *
162          * If we already have "cnt_data" filled in, we know it's
163          * all good (avoid checking the size for zero, as that
164          * is a possible size - we really should have a flag to
165          * say whether the size is valid or not!)
166          */
167         if (!src->cnt_data &&
168             diff_populate_filespec(src, CHECK_SIZE_ONLY))
169                 return 0;
170         if (!dst->cnt_data &&
171             diff_populate_filespec(dst, CHECK_SIZE_ONLY))
172                 return 0;
173
174         max_size = ((src->size > dst->size) ? src->size : dst->size);
175         base_size = ((src->size < dst->size) ? src->size : dst->size);
176         delta_size = max_size - base_size;
177
178         /* We would not consider edits that change the file size so
179          * drastically.  delta_size must be smaller than
180          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
181          *
182          * Note that base_size == 0 case is handled here already
183          * and the final score computation below would not have a
184          * divide-by-zero issue.
185          */
186         if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
187                 return 0;
188
189         if (!src->cnt_data && diff_populate_filespec(src, 0))
190                 return 0;
191         if (!dst->cnt_data && diff_populate_filespec(dst, 0))
192                 return 0;
193
194         delta_limit = (unsigned long)
195                 (base_size * (MAX_SCORE-minimum_score) / MAX_SCORE);
196         if (diffcore_count_changes(src, dst,
197                                    &src->cnt_data, &dst->cnt_data,
198                                    delta_limit,
199                                    &src_copied, &literal_added))
200                 return 0;
201
202         /* How similar are they?
203          * what percentage of material in dst are from source?
204          */
205         if (!dst->size)
206                 score = 0; /* should not happen */
207         else
208                 score = (int)(src_copied * MAX_SCORE / max_size);
209         return score;
210 }
211
212 static void record_rename_pair(int dst_index, int src_index, int score)
213 {
214         struct diff_filespec *src, *dst;
215         struct diff_filepair *dp;
216
217         if (rename_dst[dst_index].pair)
218                 die("internal error: dst already matched.");
219
220         src = rename_src[src_index].p->one;
221         src->rename_used++;
222         src->count++;
223
224         dst = rename_dst[dst_index].two;
225         dst->count++;
226
227         dp = diff_queue(NULL, src, dst);
228         dp->renamed_pair = 1;
229         if (!strcmp(src->path, dst->path))
230                 dp->score = rename_src[src_index].score;
231         else
232                 dp->score = score;
233         rename_dst[dst_index].pair = dp;
234 }
235
236 /*
237  * We sort the rename similarity matrix with the score, in descending
238  * order (the most similar first).
239  */
240 static int score_compare(const void *a_, const void *b_)
241 {
242         const struct diff_score *a = a_, *b = b_;
243
244         /* sink the unused ones to the bottom */
245         if (a->dst < 0)
246                 return (0 <= b->dst);
247         else if (b->dst < 0)
248                 return -1;
249
250         if (a->score == b->score)
251                 return b->name_score - a->name_score;
252
253         return b->score - a->score;
254 }
255
256 struct file_similarity {
257         struct hashmap_entry entry;
258         int index;
259         struct diff_filespec *filespec;
260 };
261
262 static unsigned int hash_filespec(struct diff_filespec *filespec)
263 {
264         if (!filespec->oid_valid) {
265                 if (diff_populate_filespec(filespec, 0))
266                         return 0;
267                 hash_sha1_file(filespec->data, filespec->size, "blob",
268                                filespec->oid.hash);
269         }
270         return sha1hash(filespec->oid.hash);
271 }
272
273 static int find_identical_files(struct hashmap *srcs,
274                                 int dst_index,
275                                 struct diff_options *options)
276 {
277         int renames = 0;
278
279         struct diff_filespec *target = rename_dst[dst_index].two;
280         struct file_similarity *p, *best = NULL;
281         int i = 100, best_score = -1;
282
283         /*
284          * Find the best source match for specified destination.
285          */
286         p = hashmap_get_from_hash(srcs, hash_filespec(target), NULL);
287         for (; p; p = hashmap_get_next(srcs, p)) {
288                 int score;
289                 struct diff_filespec *source = p->filespec;
290
291                 /* False hash collision? */
292                 if (oidcmp(&source->oid, &target->oid))
293                         continue;
294                 /* Non-regular files? If so, the modes must match! */
295                 if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
296                         if (source->mode != target->mode)
297                                 continue;
298                 }
299                 /* Give higher scores to sources that haven't been used already */
300                 score = !source->rename_used;
301                 if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY)
302                         continue;
303                 score += basename_same(source, target);
304                 if (score > best_score) {
305                         best = p;
306                         best_score = score;
307                         if (score == 2)
308                                 break;
309                 }
310
311                 /* Too many identical alternatives? Pick one */
312                 if (!--i)
313                         break;
314         }
315         if (best) {
316                 record_rename_pair(dst_index, best->index, MAX_SCORE);
317                 renames++;
318         }
319         return renames;
320 }
321
322 static void insert_file_table(struct hashmap *table, int index, struct diff_filespec *filespec)
323 {
324         struct file_similarity *entry = xmalloc(sizeof(*entry));
325
326         entry->index = index;
327         entry->filespec = filespec;
328
329         hashmap_entry_init(entry, hash_filespec(filespec));
330         hashmap_add(table, entry);
331 }
332
333 /*
334  * Find exact renames first.
335  *
336  * The first round matches up the up-to-date entries,
337  * and then during the second round we try to match
338  * cache-dirty entries as well.
339  */
340 static int find_exact_renames(struct diff_options *options)
341 {
342         int i, renames = 0;
343         struct hashmap file_table;
344
345         /* Add all sources to the hash table in reverse order, because
346          * later on they will be retrieved in LIFO order.
347          */
348         hashmap_init(&file_table, NULL, rename_src_nr);
349         for (i = rename_src_nr-1; i >= 0; i--)
350                 insert_file_table(&file_table, i, rename_src[i].p->one);
351
352         /* Walk the destinations and find best source match */
353         for (i = 0; i < rename_dst_nr; i++)
354                 renames += find_identical_files(&file_table, i, options);
355
356         /* Free the hash data structure and entries */
357         hashmap_free(&file_table, 1);
358
359         return renames;
360 }
361
362 #define NUM_CANDIDATE_PER_DST 4
363 static void record_if_better(struct diff_score m[], struct diff_score *o)
364 {
365         int i, worst;
366
367         /* find the worst one */
368         worst = 0;
369         for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
370                 if (score_compare(&m[i], &m[worst]) > 0)
371                         worst = i;
372
373         /* is it better than the worst one? */
374         if (score_compare(&m[worst], o) > 0)
375                 m[worst] = *o;
376 }
377
378 /*
379  * Returns:
380  * 0 if we are under the limit;
381  * 1 if we need to disable inexact rename detection;
382  * 2 if we would be under the limit if we were given -C instead of -C -C.
383  */
384 static int too_many_rename_candidates(int num_create,
385                                       struct diff_options *options)
386 {
387         int rename_limit = options->rename_limit;
388         int num_src = rename_src_nr;
389         int i;
390
391         options->needed_rename_limit = 0;
392
393         /*
394          * This basically does a test for the rename matrix not
395          * growing larger than a "rename_limit" square matrix, ie:
396          *
397          *    num_create * num_src > rename_limit * rename_limit
398          *
399          * but handles the potential overflow case specially (and we
400          * assume at least 32-bit integers)
401          */
402         if (rename_limit <= 0 || rename_limit > 32767)
403                 rename_limit = 32767;
404         if ((num_create <= rename_limit || num_src <= rename_limit) &&
405             (num_create * num_src <= rename_limit * rename_limit))
406                 return 0;
407
408         options->needed_rename_limit =
409                 num_src > num_create ? num_src : num_create;
410
411         /* Are we running under -C -C? */
412         if (!DIFF_OPT_TST(options, FIND_COPIES_HARDER))
413                 return 1;
414
415         /* Would we bust the limit if we were running under -C? */
416         for (num_src = i = 0; i < rename_src_nr; i++) {
417                 if (diff_unmodified_pair(rename_src[i].p))
418                         continue;
419                 num_src++;
420         }
421         if ((num_create <= rename_limit || num_src <= rename_limit) &&
422             (num_create * num_src <= rename_limit * rename_limit))
423                 return 2;
424         return 1;
425 }
426
427 static int find_renames(struct diff_score *mx, int dst_cnt, int minimum_score, int copies)
428 {
429         int count = 0, i;
430
431         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
432                 struct diff_rename_dst *dst;
433
434                 if ((mx[i].dst < 0) ||
435                     (mx[i].score < minimum_score))
436                         break; /* there is no more usable pair. */
437                 dst = &rename_dst[mx[i].dst];
438                 if (dst->pair)
439                         continue; /* already done, either exact or fuzzy. */
440                 if (!copies && rename_src[mx[i].src].p->one->rename_used)
441                         continue;
442                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
443                 count++;
444         }
445         return count;
446 }
447
448 void diffcore_rename(struct diff_options *options)
449 {
450         int detect_rename = options->detect_rename;
451         int minimum_score = options->rename_score;
452         struct diff_queue_struct *q = &diff_queued_diff;
453         struct diff_queue_struct outq;
454         struct diff_score *mx;
455         int i, j, rename_count, skip_unmodified = 0;
456         int num_create, dst_cnt;
457         struct progress *progress = NULL;
458
459         if (!minimum_score)
460                 minimum_score = DEFAULT_RENAME_SCORE;
461
462         for (i = 0; i < q->nr; i++) {
463                 struct diff_filepair *p = q->queue[i];
464                 if (!DIFF_FILE_VALID(p->one)) {
465                         if (!DIFF_FILE_VALID(p->two))
466                                 continue; /* unmerged */
467                         else if (options->single_follow &&
468                                  strcmp(options->single_follow, p->two->path))
469                                 continue; /* not interested */
470                         else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
471                                  is_empty_blob_sha1(p->two->oid.hash))
472                                 continue;
473                         else if (add_rename_dst(p->two) < 0) {
474                                 warning("skipping rename detection, detected"
475                                         " duplicate destination '%s'",
476                                         p->two->path);
477                                 goto cleanup;
478                         }
479                 }
480                 else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
481                          is_empty_blob_sha1(p->one->oid.hash))
482                         continue;
483                 else if (!DIFF_PAIR_UNMERGED(p) && !DIFF_FILE_VALID(p->two)) {
484                         /*
485                          * If the source is a broken "delete", and
486                          * they did not really want to get broken,
487                          * that means the source actually stays.
488                          * So we increment the "rename_used" score
489                          * by one, to indicate ourselves as a user
490                          */
491                         if (p->broken_pair && !p->score)
492                                 p->one->rename_used++;
493                         register_rename_src(p);
494                 }
495                 else if (detect_rename == DIFF_DETECT_COPY) {
496                         /*
497                          * Increment the "rename_used" score by
498                          * one, to indicate ourselves as a user.
499                          */
500                         p->one->rename_used++;
501                         register_rename_src(p);
502                 }
503         }
504         if (rename_dst_nr == 0 || rename_src_nr == 0)
505                 goto cleanup; /* nothing to do */
506
507         /*
508          * We really want to cull the candidates list early
509          * with cheap tests in order to avoid doing deltas.
510          */
511         rename_count = find_exact_renames(options);
512
513         /* Did we only want exact renames? */
514         if (minimum_score == MAX_SCORE)
515                 goto cleanup;
516
517         /*
518          * Calculate how many renames are left (but all the source
519          * files still remain as options for rename/copies!)
520          */
521         num_create = (rename_dst_nr - rename_count);
522
523         /* All done? */
524         if (!num_create)
525                 goto cleanup;
526
527         switch (too_many_rename_candidates(num_create, options)) {
528         case 1:
529                 goto cleanup;
530         case 2:
531                 options->degraded_cc_to_c = 1;
532                 skip_unmodified = 1;
533                 break;
534         default:
535                 break;
536         }
537
538         if (options->show_rename_progress) {
539                 progress = start_progress_delay(
540                                 _("Performing inexact rename detection"),
541                                 rename_dst_nr * rename_src_nr, 50, 1);
542         }
543
544         mx = xcalloc(st_mult(NUM_CANDIDATE_PER_DST, num_create), sizeof(*mx));
545         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
546                 struct diff_filespec *two = rename_dst[i].two;
547                 struct diff_score *m;
548
549                 if (rename_dst[i].pair)
550                         continue; /* dealt with exact match already. */
551
552                 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
553                 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
554                         m[j].dst = -1;
555
556                 for (j = 0; j < rename_src_nr; j++) {
557                         struct diff_filespec *one = rename_src[j].p->one;
558                         struct diff_score this_src;
559
560                         if (skip_unmodified &&
561                             diff_unmodified_pair(rename_src[j].p))
562                                 continue;
563
564                         this_src.score = estimate_similarity(one, two,
565                                                              minimum_score);
566                         this_src.name_score = basename_same(one, two);
567                         this_src.dst = i;
568                         this_src.src = j;
569                         record_if_better(m, &this_src);
570                         /*
571                          * Once we run estimate_similarity,
572                          * We do not need the text anymore.
573                          */
574                         diff_free_filespec_blob(one);
575                         diff_free_filespec_blob(two);
576                 }
577                 dst_cnt++;
578                 display_progress(progress, (i+1)*rename_src_nr);
579         }
580         stop_progress(&progress);
581
582         /* cost matrix sorted by most to least similar pair */
583         qsort(mx, dst_cnt * NUM_CANDIDATE_PER_DST, sizeof(*mx), score_compare);
584
585         rename_count += find_renames(mx, dst_cnt, minimum_score, 0);
586         if (detect_rename == DIFF_DETECT_COPY)
587                 rename_count += find_renames(mx, dst_cnt, minimum_score, 1);
588         free(mx);
589
590  cleanup:
591         /* At this point, we have found some renames and copies and they
592          * are recorded in rename_dst.  The original list is still in *q.
593          */
594         DIFF_QUEUE_CLEAR(&outq);
595         for (i = 0; i < q->nr; i++) {
596                 struct diff_filepair *p = q->queue[i];
597                 struct diff_filepair *pair_to_free = NULL;
598
599                 if (DIFF_PAIR_UNMERGED(p)) {
600                         diff_q(&outq, p);
601                 }
602                 else if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
603                         /*
604                          * Creation
605                          *
606                          * We would output this create record if it has
607                          * not been turned into a rename/copy already.
608                          */
609                         struct diff_rename_dst *dst = locate_rename_dst(p->two);
610                         if (dst && dst->pair) {
611                                 diff_q(&outq, dst->pair);
612                                 pair_to_free = p;
613                         }
614                         else
615                                 /* no matching rename/copy source, so
616                                  * record this as a creation.
617                                  */
618                                 diff_q(&outq, p);
619                 }
620                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
621                         /*
622                          * Deletion
623                          *
624                          * We would output this delete record if:
625                          *
626                          * (1) this is a broken delete and the counterpart
627                          *     broken create remains in the output; or
628                          * (2) this is not a broken delete, and rename_dst
629                          *     does not have a rename/copy to move p->one->path
630                          *     out of existence.
631                          *
632                          * Otherwise, the counterpart broken create
633                          * has been turned into a rename-edit; or
634                          * delete did not have a matching create to
635                          * begin with.
636                          */
637                         if (DIFF_PAIR_BROKEN(p)) {
638                                 /* broken delete */
639                                 struct diff_rename_dst *dst = locate_rename_dst(p->one);
640                                 if (dst && dst->pair)
641                                         /* counterpart is now rename/copy */
642                                         pair_to_free = p;
643                         }
644                         else {
645                                 if (p->one->rename_used)
646                                         /* this path remains */
647                                         pair_to_free = p;
648                         }
649
650                         if (pair_to_free)
651                                 ;
652                         else
653                                 diff_q(&outq, p);
654                 }
655                 else if (!diff_unmodified_pair(p))
656                         /* all the usual ones need to be kept */
657                         diff_q(&outq, p);
658                 else
659                         /* no need to keep unmodified pairs */
660                         pair_to_free = p;
661
662                 if (pair_to_free)
663                         diff_free_filepair(pair_to_free);
664         }
665         diff_debug_queue("done copying original", &outq);
666
667         free(q->queue);
668         *q = outq;
669         diff_debug_queue("done collapsing", q);
670
671         for (i = 0; i < rename_dst_nr; i++)
672                 free_filespec(rename_dst[i].two);
673
674         free(rename_dst);
675         rename_dst = NULL;
676         rename_dst_nr = rename_dst_alloc = 0;
677         free(rename_src);
678         rename_src = NULL;
679         rename_src_nr = rename_src_alloc = 0;
680         return;
681 }