Documentation/describe: improve one-line summary
[git.git] / diffcore-rename.c
blob4e132f1fdb68ed3c930ca8224a5403c9b406cc3b
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"
10 /* Table of rename/copy destinations */
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;
18 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
19 int insert_ok)
21 int first, last;
23 first = 0;
24 last = rename_dst_nr;
25 while (last > first) {
26 int next = (last + first) >> 1;
27 struct diff_rename_dst *dst = &(rename_dst[next]);
28 int cmp = strcmp(two->path, dst->two->path);
29 if (!cmp)
30 return dst;
31 if (cmp < 0) {
32 last = next;
33 continue;
35 first = next+1;
37 /* not found */
38 if (!insert_ok)
39 return NULL;
40 /* insert to make it at "first" */
41 ALLOC_GROW(rename_dst, rename_dst_nr + 1, rename_dst_alloc);
42 rename_dst_nr++;
43 if (first < rename_dst_nr)
44 memmove(rename_dst + first + 1, rename_dst + first,
45 (rename_dst_nr - first - 1) * sizeof(*rename_dst));
46 rename_dst[first].two = alloc_filespec(two->path);
47 fill_filespec(rename_dst[first].two, two->sha1, two->sha1_valid, two->mode);
48 rename_dst[first].pair = NULL;
49 return &(rename_dst[first]);
52 /* Table of rename/copy src files */
53 static struct diff_rename_src {
54 struct diff_filepair *p;
55 unsigned short score; /* to remember the break score */
56 } *rename_src;
57 static int rename_src_nr, rename_src_alloc;
59 static struct diff_rename_src *register_rename_src(struct diff_filepair *p)
61 int first, last;
62 struct diff_filespec *one = p->one;
63 unsigned short score = p->score;
65 first = 0;
66 last = rename_src_nr;
67 while (last > first) {
68 int next = (last + first) >> 1;
69 struct diff_rename_src *src = &(rename_src[next]);
70 int cmp = strcmp(one->path, src->p->one->path);
71 if (!cmp)
72 return src;
73 if (cmp < 0) {
74 last = next;
75 continue;
77 first = next+1;
80 /* insert to make it at "first" */
81 ALLOC_GROW(rename_src, rename_src_nr + 1, rename_src_alloc);
82 rename_src_nr++;
83 if (first < rename_src_nr)
84 memmove(rename_src + first + 1, rename_src + first,
85 (rename_src_nr - first - 1) * sizeof(*rename_src));
86 rename_src[first].p = p;
87 rename_src[first].score = score;
88 return &(rename_src[first]);
91 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
93 int src_len = strlen(src->path), dst_len = strlen(dst->path);
94 while (src_len && dst_len) {
95 char c1 = src->path[--src_len];
96 char c2 = dst->path[--dst_len];
97 if (c1 != c2)
98 return 0;
99 if (c1 == '/')
100 return 1;
102 return (!src_len || src->path[src_len - 1] == '/') &&
103 (!dst_len || dst->path[dst_len - 1] == '/');
106 struct diff_score {
107 int src; /* index in rename_src */
108 int dst; /* index in rename_dst */
109 unsigned short score;
110 short name_score;
113 static int estimate_similarity(struct diff_filespec *src,
114 struct diff_filespec *dst,
115 int minimum_score)
117 /* src points at a file that existed in the original tree (or
118 * optionally a file in the destination tree) and dst points
119 * at a newly created file. They may be quite similar, in which
120 * case we want to say src is renamed to dst or src is copied into
121 * dst, and then some edit has been applied to dst.
123 * Compare them and return how similar they are, representing
124 * the score as an integer between 0 and MAX_SCORE.
126 * When there is an exact match, it is considered a better
127 * match than anything else; the destination does not even
128 * call into this function in that case.
130 unsigned long max_size, delta_size, base_size, src_copied, literal_added;
131 unsigned long delta_limit;
132 int score;
134 /* We deal only with regular files. Symlink renames are handled
135 * only when they are exact matches --- in other words, no edits
136 * after renaming.
138 if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
139 return 0;
142 * Need to check that source and destination sizes are
143 * filled in before comparing them.
145 * If we already have "cnt_data" filled in, we know it's
146 * all good (avoid checking the size for zero, as that
147 * is a possible size - we really should have a flag to
148 * say whether the size is valid or not!)
150 if (!src->cnt_data &&
151 diff_populate_filespec(src, CHECK_SIZE_ONLY))
152 return 0;
153 if (!dst->cnt_data &&
154 diff_populate_filespec(dst, CHECK_SIZE_ONLY))
155 return 0;
157 max_size = ((src->size > dst->size) ? src->size : dst->size);
158 base_size = ((src->size < dst->size) ? src->size : dst->size);
159 delta_size = max_size - base_size;
161 /* We would not consider edits that change the file size so
162 * drastically. delta_size must be smaller than
163 * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
165 * Note that base_size == 0 case is handled here already
166 * and the final score computation below would not have a
167 * divide-by-zero issue.
169 if (max_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
170 return 0;
172 if (!src->cnt_data && diff_populate_filespec(src, 0))
173 return 0;
174 if (!dst->cnt_data && diff_populate_filespec(dst, 0))
175 return 0;
177 delta_limit = (unsigned long)
178 (base_size * (MAX_SCORE-minimum_score) / MAX_SCORE);
179 if (diffcore_count_changes(src, dst,
180 &src->cnt_data, &dst->cnt_data,
181 delta_limit,
182 &src_copied, &literal_added))
183 return 0;
185 /* How similar are they?
186 * what percentage of material in dst are from source?
188 if (!dst->size)
189 score = 0; /* should not happen */
190 else
191 score = (int)(src_copied * MAX_SCORE / max_size);
192 return score;
195 static void record_rename_pair(int dst_index, int src_index, int score)
197 struct diff_filespec *src, *dst;
198 struct diff_filepair *dp;
200 if (rename_dst[dst_index].pair)
201 die("internal error: dst already matched.");
203 src = rename_src[src_index].p->one;
204 src->rename_used++;
205 src->count++;
207 dst = rename_dst[dst_index].two;
208 dst->count++;
210 dp = diff_queue(NULL, src, dst);
211 dp->renamed_pair = 1;
212 if (!strcmp(src->path, dst->path))
213 dp->score = rename_src[src_index].score;
214 else
215 dp->score = score;
216 rename_dst[dst_index].pair = dp;
220 * We sort the rename similarity matrix with the score, in descending
221 * order (the most similar first).
223 static int score_compare(const void *a_, const void *b_)
225 const struct diff_score *a = a_, *b = b_;
227 /* sink the unused ones to the bottom */
228 if (a->dst < 0)
229 return (0 <= b->dst);
230 else if (b->dst < 0)
231 return -1;
233 if (a->score == b->score)
234 return b->name_score - a->name_score;
236 return b->score - a->score;
239 struct file_similarity {
240 struct hashmap_entry entry;
241 int index;
242 struct diff_filespec *filespec;
245 static unsigned int hash_filespec(struct diff_filespec *filespec)
247 if (!filespec->sha1_valid) {
248 if (diff_populate_filespec(filespec, 0))
249 return 0;
250 hash_sha1_file(filespec->data, filespec->size, "blob", filespec->sha1);
252 return sha1hash(filespec->sha1);
255 static int find_identical_files(struct hashmap *srcs,
256 int dst_index,
257 struct diff_options *options)
259 int renames = 0;
261 struct diff_filespec *target = rename_dst[dst_index].two;
262 struct file_similarity *p, *best = NULL;
263 int i = 100, best_score = -1;
266 * Find the best source match for specified destination.
268 p = hashmap_get_from_hash(srcs, hash_filespec(target), NULL);
269 for (; p; p = hashmap_get_next(srcs, p)) {
270 int score;
271 struct diff_filespec *source = p->filespec;
273 /* False hash collision? */
274 if (hashcmp(source->sha1, target->sha1))
275 continue;
276 /* Non-regular files? If so, the modes must match! */
277 if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
278 if (source->mode != target->mode)
279 continue;
281 /* Give higher scores to sources that haven't been used already */
282 score = !source->rename_used;
283 if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY)
284 continue;
285 score += basename_same(source, target);
286 if (score > best_score) {
287 best = p;
288 best_score = score;
289 if (score == 2)
290 break;
293 /* Too many identical alternatives? Pick one */
294 if (!--i)
295 break;
297 if (best) {
298 record_rename_pair(dst_index, best->index, MAX_SCORE);
299 renames++;
301 return renames;
304 static void insert_file_table(struct hashmap *table, int index, struct diff_filespec *filespec)
306 struct file_similarity *entry = xmalloc(sizeof(*entry));
308 entry->index = index;
309 entry->filespec = filespec;
311 hashmap_entry_init(entry, hash_filespec(filespec));
312 hashmap_add(table, entry);
316 * Find exact renames first.
318 * The first round matches up the up-to-date entries,
319 * and then during the second round we try to match
320 * cache-dirty entries as well.
322 static int find_exact_renames(struct diff_options *options)
324 int i, renames = 0;
325 struct hashmap file_table;
327 /* Add all sources to the hash table */
328 hashmap_init(&file_table, NULL, rename_src_nr);
329 for (i = 0; i < rename_src_nr; i++)
330 insert_file_table(&file_table, i, rename_src[i].p->one);
332 /* Walk the destinations and find best source match */
333 for (i = 0; i < rename_dst_nr; i++)
334 renames += find_identical_files(&file_table, i, options);
336 /* Free the hash data structure and entries */
337 hashmap_free(&file_table, 1);
339 return renames;
342 #define NUM_CANDIDATE_PER_DST 4
343 static void record_if_better(struct diff_score m[], struct diff_score *o)
345 int i, worst;
347 /* find the worst one */
348 worst = 0;
349 for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
350 if (score_compare(&m[i], &m[worst]) > 0)
351 worst = i;
353 /* is it better than the worst one? */
354 if (score_compare(&m[worst], o) > 0)
355 m[worst] = *o;
359 * Returns:
360 * 0 if we are under the limit;
361 * 1 if we need to disable inexact rename detection;
362 * 2 if we would be under the limit if we were given -C instead of -C -C.
364 static int too_many_rename_candidates(int num_create,
365 struct diff_options *options)
367 int rename_limit = options->rename_limit;
368 int num_src = rename_src_nr;
369 int i;
371 options->needed_rename_limit = 0;
374 * This basically does a test for the rename matrix not
375 * growing larger than a "rename_limit" square matrix, ie:
377 * num_create * num_src > rename_limit * rename_limit
379 * but handles the potential overflow case specially (and we
380 * assume at least 32-bit integers)
382 if (rename_limit <= 0 || rename_limit > 32767)
383 rename_limit = 32767;
384 if ((num_create <= rename_limit || num_src <= rename_limit) &&
385 (num_create * num_src <= rename_limit * rename_limit))
386 return 0;
388 options->needed_rename_limit =
389 num_src > num_create ? num_src : num_create;
391 /* Are we running under -C -C? */
392 if (!DIFF_OPT_TST(options, FIND_COPIES_HARDER))
393 return 1;
395 /* Would we bust the limit if we were running under -C? */
396 for (num_src = i = 0; i < rename_src_nr; i++) {
397 if (diff_unmodified_pair(rename_src[i].p))
398 continue;
399 num_src++;
401 if ((num_create <= rename_limit || num_src <= rename_limit) &&
402 (num_create * num_src <= rename_limit * rename_limit))
403 return 2;
404 return 1;
407 static int find_renames(struct diff_score *mx, int dst_cnt, int minimum_score, int copies)
409 int count = 0, i;
411 for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
412 struct diff_rename_dst *dst;
414 if ((mx[i].dst < 0) ||
415 (mx[i].score < minimum_score))
416 break; /* there is no more usable pair. */
417 dst = &rename_dst[mx[i].dst];
418 if (dst->pair)
419 continue; /* already done, either exact or fuzzy. */
420 if (!copies && rename_src[mx[i].src].p->one->rename_used)
421 continue;
422 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
423 count++;
425 return count;
428 void diffcore_rename(struct diff_options *options)
430 int detect_rename = options->detect_rename;
431 int minimum_score = options->rename_score;
432 struct diff_queue_struct *q = &diff_queued_diff;
433 struct diff_queue_struct outq;
434 struct diff_score *mx;
435 int i, j, rename_count, skip_unmodified = 0;
436 int num_create, dst_cnt;
437 struct progress *progress = NULL;
439 if (!minimum_score)
440 minimum_score = DEFAULT_RENAME_SCORE;
442 for (i = 0; i < q->nr; i++) {
443 struct diff_filepair *p = q->queue[i];
444 if (!DIFF_FILE_VALID(p->one)) {
445 if (!DIFF_FILE_VALID(p->two))
446 continue; /* unmerged */
447 else if (options->single_follow &&
448 strcmp(options->single_follow, p->two->path))
449 continue; /* not interested */
450 else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
451 is_empty_blob_sha1(p->two->sha1))
452 continue;
453 else
454 locate_rename_dst(p->two, 1);
456 else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
457 is_empty_blob_sha1(p->one->sha1))
458 continue;
459 else if (!DIFF_PAIR_UNMERGED(p) && !DIFF_FILE_VALID(p->two)) {
461 * If the source is a broken "delete", and
462 * they did not really want to get broken,
463 * that means the source actually stays.
464 * So we increment the "rename_used" score
465 * by one, to indicate ourselves as a user
467 if (p->broken_pair && !p->score)
468 p->one->rename_used++;
469 register_rename_src(p);
471 else if (detect_rename == DIFF_DETECT_COPY) {
473 * Increment the "rename_used" score by
474 * one, to indicate ourselves as a user.
476 p->one->rename_used++;
477 register_rename_src(p);
480 if (rename_dst_nr == 0 || rename_src_nr == 0)
481 goto cleanup; /* nothing to do */
484 * We really want to cull the candidates list early
485 * with cheap tests in order to avoid doing deltas.
487 rename_count = find_exact_renames(options);
489 /* Did we only want exact renames? */
490 if (minimum_score == MAX_SCORE)
491 goto cleanup;
494 * Calculate how many renames are left (but all the source
495 * files still remain as options for rename/copies!)
497 num_create = (rename_dst_nr - rename_count);
499 /* All done? */
500 if (!num_create)
501 goto cleanup;
503 switch (too_many_rename_candidates(num_create, options)) {
504 case 1:
505 goto cleanup;
506 case 2:
507 options->degraded_cc_to_c = 1;
508 skip_unmodified = 1;
509 break;
510 default:
511 break;
514 if (options->show_rename_progress) {
515 progress = start_progress_delay(
516 _("Performing inexact rename detection"),
517 rename_dst_nr * rename_src_nr, 50, 1);
520 mx = xcalloc(num_create * NUM_CANDIDATE_PER_DST, sizeof(*mx));
521 for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
522 struct diff_filespec *two = rename_dst[i].two;
523 struct diff_score *m;
525 if (rename_dst[i].pair)
526 continue; /* dealt with exact match already. */
528 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
529 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
530 m[j].dst = -1;
532 for (j = 0; j < rename_src_nr; j++) {
533 struct diff_filespec *one = rename_src[j].p->one;
534 struct diff_score this_src;
536 if (skip_unmodified &&
537 diff_unmodified_pair(rename_src[j].p))
538 continue;
540 this_src.score = estimate_similarity(one, two,
541 minimum_score);
542 this_src.name_score = basename_same(one, two);
543 this_src.dst = i;
544 this_src.src = j;
545 record_if_better(m, &this_src);
547 * Once we run estimate_similarity,
548 * We do not need the text anymore.
550 diff_free_filespec_blob(one);
551 diff_free_filespec_blob(two);
553 dst_cnt++;
554 display_progress(progress, (i+1)*rename_src_nr);
556 stop_progress(&progress);
558 /* cost matrix sorted by most to least similar pair */
559 qsort(mx, dst_cnt * NUM_CANDIDATE_PER_DST, sizeof(*mx), score_compare);
561 rename_count += find_renames(mx, dst_cnt, minimum_score, 0);
562 if (detect_rename == DIFF_DETECT_COPY)
563 rename_count += find_renames(mx, dst_cnt, minimum_score, 1);
564 free(mx);
566 cleanup:
567 /* At this point, we have found some renames and copies and they
568 * are recorded in rename_dst. The original list is still in *q.
570 DIFF_QUEUE_CLEAR(&outq);
571 for (i = 0; i < q->nr; i++) {
572 struct diff_filepair *p = q->queue[i];
573 struct diff_filepair *pair_to_free = NULL;
575 if (DIFF_PAIR_UNMERGED(p)) {
576 diff_q(&outq, p);
578 else if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
580 * Creation
582 * We would output this create record if it has
583 * not been turned into a rename/copy already.
585 struct diff_rename_dst *dst =
586 locate_rename_dst(p->two, 0);
587 if (dst && dst->pair) {
588 diff_q(&outq, dst->pair);
589 pair_to_free = p;
591 else
592 /* no matching rename/copy source, so
593 * record this as a creation.
595 diff_q(&outq, p);
597 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
599 * Deletion
601 * We would output this delete record if:
603 * (1) this is a broken delete and the counterpart
604 * broken create remains in the output; or
605 * (2) this is not a broken delete, and rename_dst
606 * does not have a rename/copy to move p->one->path
607 * out of existence.
609 * Otherwise, the counterpart broken create
610 * has been turned into a rename-edit; or
611 * delete did not have a matching create to
612 * begin with.
614 if (DIFF_PAIR_BROKEN(p)) {
615 /* broken delete */
616 struct diff_rename_dst *dst =
617 locate_rename_dst(p->one, 0);
618 if (dst && dst->pair)
619 /* counterpart is now rename/copy */
620 pair_to_free = p;
622 else {
623 if (p->one->rename_used)
624 /* this path remains */
625 pair_to_free = p;
628 if (pair_to_free)
630 else
631 diff_q(&outq, p);
633 else if (!diff_unmodified_pair(p))
634 /* all the usual ones need to be kept */
635 diff_q(&outq, p);
636 else
637 /* no need to keep unmodified pairs */
638 pair_to_free = p;
640 if (pair_to_free)
641 diff_free_filepair(pair_to_free);
643 diff_debug_queue("done copying original", &outq);
645 free(q->queue);
646 *q = outq;
647 diff_debug_queue("done collapsing", q);
649 for (i = 0; i < rename_dst_nr; i++)
650 free_filespec(rename_dst[i].two);
652 free(rename_dst);
653 rename_dst = NULL;
654 rename_dst_nr = rename_dst_alloc = 0;
655 free(rename_src);
656 rename_src = NULL;
657 rename_src_nr = rename_src_alloc = 0;
658 return;