reflog expire --stale-fix: be generous about missing objects
[git] / diffcore-rename.c
1 /*
2  *
3  * Copyright (C) 2005 Junio C Hamano
4  */
5 #include "cache.h"
6 #include "diff.h"
7 #include "diffcore.h"
8 #include "object-store.h"
9 #include "hashmap.h"
10 #include "progress.h"
11 #include "promisor-remote.h"
12 #include "strmap.h"
13
14 /* Table of rename/copy destinations */
15
16 static struct diff_rename_dst {
17         struct diff_filepair *p;
18         struct diff_filespec *filespec_to_free;
19         int is_rename; /* false -> just a create; true -> rename or copy */
20 } *rename_dst;
21 static int rename_dst_nr, rename_dst_alloc;
22 /* Mapping from break source pathname to break destination index */
23 static struct strintmap *break_idx = NULL;
24
25 static struct diff_rename_dst *locate_rename_dst(struct diff_filepair *p)
26 {
27         /* Lookup by p->ONE->path */
28         int idx = break_idx ? strintmap_get(break_idx, p->one->path) : -1;
29         return (idx == -1) ? NULL : &rename_dst[idx];
30 }
31
32 /*
33  * Returns 0 on success, -1 if we found a duplicate.
34  */
35 static int add_rename_dst(struct diff_filepair *p)
36 {
37         ALLOC_GROW(rename_dst, rename_dst_nr + 1, rename_dst_alloc);
38         rename_dst[rename_dst_nr].p = p;
39         rename_dst[rename_dst_nr].filespec_to_free = NULL;
40         rename_dst[rename_dst_nr].is_rename = 0;
41         rename_dst_nr++;
42         return 0;
43 }
44
45 /* Table of rename/copy src files */
46 static struct diff_rename_src {
47         struct diff_filepair *p;
48         unsigned short score; /* to remember the break score */
49 } *rename_src;
50 static int rename_src_nr, rename_src_alloc;
51
52 static void register_rename_src(struct diff_filepair *p)
53 {
54         if (p->broken_pair) {
55                 if (!break_idx) {
56                         break_idx = xmalloc(sizeof(*break_idx));
57                         strintmap_init(break_idx, -1);
58                 }
59                 strintmap_set(break_idx, p->one->path, rename_dst_nr);
60         }
61
62         ALLOC_GROW(rename_src, rename_src_nr + 1, rename_src_alloc);
63         rename_src[rename_src_nr].p = p;
64         rename_src[rename_src_nr].score = p->score;
65         rename_src_nr++;
66 }
67
68 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
69 {
70         int src_len = strlen(src->path), dst_len = strlen(dst->path);
71         while (src_len && dst_len) {
72                 char c1 = src->path[--src_len];
73                 char c2 = dst->path[--dst_len];
74                 if (c1 != c2)
75                         return 0;
76                 if (c1 == '/')
77                         return 1;
78         }
79         return (!src_len || src->path[src_len - 1] == '/') &&
80                 (!dst_len || dst->path[dst_len - 1] == '/');
81 }
82
83 struct diff_score {
84         int src; /* index in rename_src */
85         int dst; /* index in rename_dst */
86         unsigned short score;
87         short name_score;
88 };
89
90 struct prefetch_options {
91         struct repository *repo;
92         int skip_unmodified;
93 };
94 static void prefetch(void *prefetch_options)
95 {
96         struct prefetch_options *options = prefetch_options;
97         int i;
98         struct oid_array to_fetch = OID_ARRAY_INIT;
99
100         for (i = 0; i < rename_dst_nr; i++) {
101                 if (rename_dst[i].p->renamed_pair)
102                         /*
103                          * The loop in diffcore_rename() will not need these
104                          * blobs, so skip prefetching.
105                          */
106                         continue; /* already found exact match */
107                 diff_add_if_missing(options->repo, &to_fetch,
108                                     rename_dst[i].p->two);
109         }
110         for (i = 0; i < rename_src_nr; i++) {
111                 if (options->skip_unmodified &&
112                     diff_unmodified_pair(rename_src[i].p))
113                         /*
114                          * The loop in diffcore_rename() will not need these
115                          * blobs, so skip prefetching.
116                          */
117                         continue;
118                 diff_add_if_missing(options->repo, &to_fetch,
119                                     rename_src[i].p->one);
120         }
121         promisor_remote_get_direct(options->repo, to_fetch.oid, to_fetch.nr);
122         oid_array_clear(&to_fetch);
123 }
124
125 static int estimate_similarity(struct repository *r,
126                                struct diff_filespec *src,
127                                struct diff_filespec *dst,
128                                int minimum_score,
129                                int skip_unmodified)
130 {
131         /* src points at a file that existed in the original tree (or
132          * optionally a file in the destination tree) and dst points
133          * at a newly created file.  They may be quite similar, in which
134          * case we want to say src is renamed to dst or src is copied into
135          * dst, and then some edit has been applied to dst.
136          *
137          * Compare them and return how similar they are, representing
138          * the score as an integer between 0 and MAX_SCORE.
139          *
140          * When there is an exact match, it is considered a better
141          * match than anything else; the destination does not even
142          * call into this function in that case.
143          */
144         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
145         int score;
146         struct diff_populate_filespec_options dpf_options = {
147                 .check_size_only = 1
148         };
149         struct prefetch_options prefetch_options = {r, skip_unmodified};
150
151         if (r == the_repository && has_promisor_remote()) {
152                 dpf_options.missing_object_cb = prefetch;
153                 dpf_options.missing_object_data = &prefetch_options;
154         }
155
156         /* We deal only with regular files.  Symlink renames are handled
157          * only when they are exact matches --- in other words, no edits
158          * after renaming.
159          */
160         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
161                 return 0;
162
163         /*
164          * Need to check that source and destination sizes are
165          * filled in before comparing them.
166          *
167          * If we already have "cnt_data" filled in, we know it's
168          * all good (avoid checking the size for zero, as that
169          * is a possible size - we really should have a flag to
170          * say whether the size is valid or not!)
171          */
172         if (!src->cnt_data &&
173             diff_populate_filespec(r, src, &dpf_options))
174                 return 0;
175         if (!dst->cnt_data &&
176             diff_populate_filespec(r, dst, &dpf_options))
177                 return 0;
178
179         max_size = ((src->size > dst->size) ? src->size : dst->size);
180         base_size = ((src->size < dst->size) ? src->size : dst->size);
181         delta_size = max_size - base_size;
182
183         /* We would not consider edits that change the file size so
184          * drastically.  delta_size must be smaller than
185          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
186          *
187          * Note that base_size == 0 case is handled here already
188          * and the final score computation below would not have a
189          * divide-by-zero issue.
190          */
191         if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
192                 return 0;
193
194         dpf_options.check_size_only = 0;
195
196         if (!src->cnt_data && diff_populate_filespec(r, src, &dpf_options))
197                 return 0;
198         if (!dst->cnt_data && diff_populate_filespec(r, dst, &dpf_options))
199                 return 0;
200
201         if (diffcore_count_changes(r, src, dst,
202                                    &src->cnt_data, &dst->cnt_data,
203                                    &src_copied, &literal_added))
204                 return 0;
205
206         /* How similar are they?
207          * what percentage of material in dst are from source?
208          */
209         if (!dst->size)
210                 score = 0; /* should not happen */
211         else
212                 score = (int)(src_copied * MAX_SCORE / max_size);
213         return score;
214 }
215
216 static void record_rename_pair(int dst_index, int src_index, int score)
217 {
218         struct diff_filepair *src = rename_src[src_index].p;
219         struct diff_filepair *dst = rename_dst[dst_index].p;
220
221         if (dst->renamed_pair)
222                 die("internal error: dst already matched.");
223
224         src->one->rename_used++;
225         src->one->count++;
226
227         rename_dst[dst_index].filespec_to_free = dst->one;
228         rename_dst[dst_index].is_rename = 1;
229
230         dst->one = src->one;
231         dst->renamed_pair = 1;
232         if (!strcmp(dst->one->path, dst->two->path))
233                 dst->score = rename_src[src_index].score;
234         else
235                 dst->score = score;
236 }
237
238 /*
239  * We sort the rename similarity matrix with the score, in descending
240  * order (the most similar first).
241  */
242 static int score_compare(const void *a_, const void *b_)
243 {
244         const struct diff_score *a = a_, *b = b_;
245
246         /* sink the unused ones to the bottom */
247         if (a->dst < 0)
248                 return (0 <= b->dst);
249         else if (b->dst < 0)
250                 return -1;
251
252         if (a->score == b->score)
253                 return b->name_score - a->name_score;
254
255         return b->score - a->score;
256 }
257
258 struct file_similarity {
259         struct hashmap_entry entry;
260         int index;
261         struct diff_filespec *filespec;
262 };
263
264 static unsigned int hash_filespec(struct repository *r,
265                                   struct diff_filespec *filespec)
266 {
267         if (!filespec->oid_valid) {
268                 if (diff_populate_filespec(r, filespec, NULL))
269                         return 0;
270                 hash_object_file(r->hash_algo, filespec->data, filespec->size,
271                                  "blob", &filespec->oid);
272         }
273         return oidhash(&filespec->oid);
274 }
275
276 static int find_identical_files(struct hashmap *srcs,
277                                 int dst_index,
278                                 struct diff_options *options)
279 {
280         int renames = 0;
281         struct diff_filespec *target = rename_dst[dst_index].p->two;
282         struct file_similarity *p, *best = NULL;
283         int i = 100, best_score = -1;
284         unsigned int hash = hash_filespec(options->repo, target);
285
286         /*
287          * Find the best source match for specified destination.
288          */
289         p = hashmap_get_entry_from_hash(srcs, hash, NULL,
290                                         struct file_similarity, entry);
291         hashmap_for_each_entry_from(srcs, p, entry) {
292                 int score;
293                 struct diff_filespec *source = p->filespec;
294
295                 /* False hash collision? */
296                 if (!oideq(&source->oid, &target->oid))
297                         continue;
298                 /* Non-regular files? If so, the modes must match! */
299                 if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
300                         if (source->mode != target->mode)
301                                 continue;
302                 }
303                 /* Give higher scores to sources that haven't been used already */
304                 score = !source->rename_used;
305                 if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY)
306                         continue;
307                 score += basename_same(source, target);
308                 if (score > best_score) {
309                         best = p;
310                         best_score = score;
311                         if (score == 2)
312                                 break;
313                 }
314
315                 /* Too many identical alternatives? Pick one */
316                 if (!--i)
317                         break;
318         }
319         if (best) {
320                 record_rename_pair(dst_index, best->index, MAX_SCORE);
321                 renames++;
322         }
323         return renames;
324 }
325
326 static void insert_file_table(struct repository *r,
327                               struct hashmap *table, int index,
328                               struct diff_filespec *filespec)
329 {
330         struct file_similarity *entry = xmalloc(sizeof(*entry));
331
332         entry->index = index;
333         entry->filespec = filespec;
334
335         hashmap_entry_init(&entry->entry, hash_filespec(r, filespec));
336         hashmap_add(table, &entry->entry);
337 }
338
339 /*
340  * Find exact renames first.
341  *
342  * The first round matches up the up-to-date entries,
343  * and then during the second round we try to match
344  * cache-dirty entries as well.
345  */
346 static int find_exact_renames(struct diff_options *options)
347 {
348         int i, renames = 0;
349         struct hashmap file_table;
350
351         /* Add all sources to the hash table in reverse order, because
352          * later on they will be retrieved in LIFO order.
353          */
354         hashmap_init(&file_table, NULL, NULL, rename_src_nr);
355         for (i = rename_src_nr-1; i >= 0; i--)
356                 insert_file_table(options->repo,
357                                   &file_table, i,
358                                   rename_src[i].p->one);
359
360         /* Walk the destinations and find best source match */
361         for (i = 0; i < rename_dst_nr; i++)
362                 renames += find_identical_files(&file_table, i, options);
363
364         /* Free the hash data structure and entries */
365         hashmap_clear_and_free(&file_table, struct file_similarity, entry);
366
367         return renames;
368 }
369
370 #define NUM_CANDIDATE_PER_DST 4
371 static void record_if_better(struct diff_score m[], struct diff_score *o)
372 {
373         int i, worst;
374
375         /* find the worst one */
376         worst = 0;
377         for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
378                 if (score_compare(&m[i], &m[worst]) > 0)
379                         worst = i;
380
381         /* is it better than the worst one? */
382         if (score_compare(&m[worst], o) > 0)
383                 m[worst] = *o;
384 }
385
386 /*
387  * Returns:
388  * 0 if we are under the limit;
389  * 1 if we need to disable inexact rename detection;
390  * 2 if we would be under the limit if we were given -C instead of -C -C.
391  */
392 static int too_many_rename_candidates(int num_destinations, int num_sources,
393                                       struct diff_options *options)
394 {
395         int rename_limit = options->rename_limit;
396         int i, limited_sources;
397
398         options->needed_rename_limit = 0;
399
400         /*
401          * This basically does a test for the rename matrix not
402          * growing larger than a "rename_limit" square matrix, ie:
403          *
404          *    num_destinations * num_sources > rename_limit * rename_limit
405          *
406          * We use st_mult() to check overflow conditions; in the
407          * exceptional circumstance that size_t isn't large enough to hold
408          * the multiplication, the system won't be able to allocate enough
409          * memory for the matrix anyway.
410          */
411         if (rename_limit <= 0)
412                 rename_limit = 32767;
413         if (st_mult(num_destinations, num_sources)
414             <= st_mult(rename_limit, rename_limit))
415                 return 0;
416
417         options->needed_rename_limit =
418                 num_sources > num_destinations ? num_sources : num_destinations;
419
420         /* Are we running under -C -C? */
421         if (!options->flags.find_copies_harder)
422                 return 1;
423
424         /* Would we bust the limit if we were running under -C? */
425         for (limited_sources = i = 0; i < num_sources; i++) {
426                 if (diff_unmodified_pair(rename_src[i].p))
427                         continue;
428                 limited_sources++;
429         }
430         if (st_mult(num_destinations, limited_sources)
431             <= st_mult(rename_limit, rename_limit))
432                 return 2;
433         return 1;
434 }
435
436 static int find_renames(struct diff_score *mx, int dst_cnt, int minimum_score, int copies)
437 {
438         int count = 0, i;
439
440         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
441                 struct diff_rename_dst *dst;
442
443                 if ((mx[i].dst < 0) ||
444                     (mx[i].score < minimum_score))
445                         break; /* there is no more usable pair. */
446                 dst = &rename_dst[mx[i].dst];
447                 if (dst->is_rename)
448                         continue; /* already done, either exact or fuzzy. */
449                 if (!copies && rename_src[mx[i].src].p->one->rename_used)
450                         continue;
451                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
452                 count++;
453         }
454         return count;
455 }
456
457 void diffcore_rename(struct diff_options *options)
458 {
459         int detect_rename = options->detect_rename;
460         int minimum_score = options->rename_score;
461         struct diff_queue_struct *q = &diff_queued_diff;
462         struct diff_queue_struct outq;
463         struct diff_score *mx;
464         int i, j, rename_count, skip_unmodified = 0;
465         int num_destinations, dst_cnt;
466         struct progress *progress = NULL;
467
468         if (!minimum_score)
469                 minimum_score = DEFAULT_RENAME_SCORE;
470
471         for (i = 0; i < q->nr; i++) {
472                 struct diff_filepair *p = q->queue[i];
473                 if (!DIFF_FILE_VALID(p->one)) {
474                         if (!DIFF_FILE_VALID(p->two))
475                                 continue; /* unmerged */
476                         else if (options->single_follow &&
477                                  strcmp(options->single_follow, p->two->path))
478                                 continue; /* not interested */
479                         else if (!options->flags.rename_empty &&
480                                  is_empty_blob_oid(&p->two->oid))
481                                 continue;
482                         else if (add_rename_dst(p) < 0) {
483                                 warning("skipping rename detection, detected"
484                                         " duplicate destination '%s'",
485                                         p->two->path);
486                                 goto cleanup;
487                         }
488                 }
489                 else if (!options->flags.rename_empty &&
490                          is_empty_blob_oid(&p->one->oid))
491                         continue;
492                 else if (!DIFF_PAIR_UNMERGED(p) && !DIFF_FILE_VALID(p->two)) {
493                         /*
494                          * If the source is a broken "delete", and
495                          * they did not really want to get broken,
496                          * that means the source actually stays.
497                          * So we increment the "rename_used" score
498                          * by one, to indicate ourselves as a user
499                          */
500                         if (p->broken_pair && !p->score)
501                                 p->one->rename_used++;
502                         register_rename_src(p);
503                 }
504                 else if (detect_rename == DIFF_DETECT_COPY) {
505                         /*
506                          * Increment the "rename_used" score by
507                          * one, to indicate ourselves as a user.
508                          */
509                         p->one->rename_used++;
510                         register_rename_src(p);
511                 }
512         }
513         if (rename_dst_nr == 0 || rename_src_nr == 0)
514                 goto cleanup; /* nothing to do */
515
516         /*
517          * We really want to cull the candidates list early
518          * with cheap tests in order to avoid doing deltas.
519          */
520         rename_count = find_exact_renames(options);
521
522         /* Did we only want exact renames? */
523         if (minimum_score == MAX_SCORE)
524                 goto cleanup;
525
526         /*
527          * Calculate how many renames are left (but all the source
528          * files still remain as options for rename/copies!)
529          */
530         num_destinations = (rename_dst_nr - rename_count);
531
532         /* All done? */
533         if (!num_destinations)
534                 goto cleanup;
535
536         switch (too_many_rename_candidates(num_destinations, rename_src_nr,
537                                            options)) {
538         case 1:
539                 goto cleanup;
540         case 2:
541                 options->degraded_cc_to_c = 1;
542                 skip_unmodified = 1;
543                 break;
544         default:
545                 break;
546         }
547
548         if (options->show_rename_progress) {
549                 progress = start_delayed_progress(
550                                 _("Performing inexact rename detection"),
551                                 (uint64_t)num_destinations * (uint64_t)rename_src_nr);
552         }
553
554         mx = xcalloc(st_mult(NUM_CANDIDATE_PER_DST, num_destinations),
555                      sizeof(*mx));
556         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
557                 struct diff_filespec *two = rename_dst[i].p->two;
558                 struct diff_score *m;
559
560                 if (rename_dst[i].is_rename)
561                         continue; /* dealt with exact match already. */
562
563                 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
564                 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
565                         m[j].dst = -1;
566
567                 for (j = 0; j < rename_src_nr; j++) {
568                         struct diff_filespec *one = rename_src[j].p->one;
569                         struct diff_score this_src;
570
571                         if (skip_unmodified &&
572                             diff_unmodified_pair(rename_src[j].p))
573                                 continue;
574
575                         this_src.score = estimate_similarity(options->repo,
576                                                              one, two,
577                                                              minimum_score,
578                                                              skip_unmodified);
579                         this_src.name_score = basename_same(one, two);
580                         this_src.dst = i;
581                         this_src.src = j;
582                         record_if_better(m, &this_src);
583                         /*
584                          * Once we run estimate_similarity,
585                          * We do not need the text anymore.
586                          */
587                         diff_free_filespec_blob(one);
588                         diff_free_filespec_blob(two);
589                 }
590                 dst_cnt++;
591                 display_progress(progress,
592                                  (uint64_t)dst_cnt * (uint64_t)rename_src_nr);
593         }
594         stop_progress(&progress);
595
596         /* cost matrix sorted by most to least similar pair */
597         STABLE_QSORT(mx, dst_cnt * NUM_CANDIDATE_PER_DST, score_compare);
598
599         rename_count += find_renames(mx, dst_cnt, minimum_score, 0);
600         if (detect_rename == DIFF_DETECT_COPY)
601                 rename_count += find_renames(mx, dst_cnt, minimum_score, 1);
602         free(mx);
603
604  cleanup:
605         /* At this point, we have found some renames and copies and they
606          * are recorded in rename_dst.  The original list is still in *q.
607          */
608         DIFF_QUEUE_CLEAR(&outq);
609         for (i = 0; i < q->nr; i++) {
610                 struct diff_filepair *p = q->queue[i];
611                 struct diff_filepair *pair_to_free = NULL;
612
613                 if (DIFF_PAIR_UNMERGED(p)) {
614                         diff_q(&outq, p);
615                 }
616                 else if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
617                         /* Creation */
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);
640                                 if (!dst)
641                                         BUG("tracking failed somehow; failed to find associated dst for broken pair");
642                                 if (dst->is_rename)
643                                         /* counterpart is now rename/copy */
644                                         pair_to_free = p;
645                         }
646                         else {
647                                 if (p->one->rename_used)
648                                         /* this path remains */
649                                         pair_to_free = p;
650                         }
651
652                         if (!pair_to_free)
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; FIXME: remove earlier? */
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                 if (rename_dst[i].filespec_to_free)
673                         free_filespec(rename_dst[i].filespec_to_free);
674
675         FREE_AND_NULL(rename_dst);
676         rename_dst_nr = rename_dst_alloc = 0;
677         FREE_AND_NULL(rename_src);
678         rename_src_nr = rename_src_alloc = 0;
679         if (break_idx) {
680                 strintmap_clear(break_idx);
681                 FREE_AND_NULL(break_idx);
682         }
683         return;
684 }