Merge branch 'ew/rerere'
[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
8 /* Table of rename/copy destinations */
9
10 static struct diff_rename_dst {
11         struct diff_filespec *two;
12         struct diff_filepair *pair;
13 } *rename_dst;
14 static int rename_dst_nr, rename_dst_alloc;
15
16 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
17                                                  int insert_ok)
18 {
19         int first, last;
20
21         first = 0;
22         last = rename_dst_nr;
23         while (last > first) {
24                 int next = (last + first) >> 1;
25                 struct diff_rename_dst *dst = &(rename_dst[next]);
26                 int cmp = strcmp(two->path, dst->two->path);
27                 if (!cmp)
28                         return dst;
29                 if (cmp < 0) {
30                         last = next;
31                         continue;
32                 }
33                 first = next+1;
34         }
35         /* not found */
36         if (!insert_ok)
37                 return NULL;
38         /* insert to make it at "first" */
39         if (rename_dst_alloc <= rename_dst_nr) {
40                 rename_dst_alloc = alloc_nr(rename_dst_alloc);
41                 rename_dst = xrealloc(rename_dst,
42                                       rename_dst_alloc * sizeof(*rename_dst));
43         }
44         rename_dst_nr++;
45         if (first < rename_dst_nr)
46                 memmove(rename_dst + first + 1, rename_dst + first,
47                         (rename_dst_nr - first - 1) * sizeof(*rename_dst));
48         rename_dst[first].two = alloc_filespec(two->path);
49         fill_filespec(rename_dst[first].two, two->sha1, two->mode);
50         rename_dst[first].pair = NULL;
51         return &(rename_dst[first]);
52 }
53
54 /* Table of rename/copy src files */
55 static struct diff_rename_src {
56         struct diff_filespec *one;
57         unsigned short score; /* to remember the break score */
58         unsigned src_path_left : 1;
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                                                    int src_path_left,
64                                                    unsigned short score)
65 {
66         int first, last;
67
68         first = 0;
69         last = rename_src_nr;
70         while (last > first) {
71                 int next = (last + first) >> 1;
72                 struct diff_rename_src *src = &(rename_src[next]);
73                 int cmp = strcmp(one->path, src->one->path);
74                 if (!cmp)
75                         return src;
76                 if (cmp < 0) {
77                         last = next;
78                         continue;
79                 }
80                 first = next+1;
81         }
82
83         /* insert to make it at "first" */
84         if (rename_src_alloc <= rename_src_nr) {
85                 rename_src_alloc = alloc_nr(rename_src_alloc);
86                 rename_src = xrealloc(rename_src,
87                                       rename_src_alloc * sizeof(*rename_src));
88         }
89         rename_src_nr++;
90         if (first < rename_src_nr)
91                 memmove(rename_src + first + 1, rename_src + first,
92                         (rename_src_nr - first - 1) * sizeof(*rename_src));
93         rename_src[first].one = one;
94         rename_src[first].score = score;
95         rename_src[first].src_path_left = src_path_left;
96         return &(rename_src[first]);
97 }
98
99 static int is_exact_match(struct diff_filespec *src,
100                           struct diff_filespec *dst,
101                           int contents_too)
102 {
103         if (src->sha1_valid && dst->sha1_valid &&
104             !hashcmp(src->sha1, dst->sha1))
105                 return 1;
106         if (!contents_too)
107                 return 0;
108         if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
109                 return 0;
110         if (src->size != dst->size)
111                 return 0;
112         if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
113                 return 0;
114         if (src->size == dst->size &&
115             !memcmp(src->data, dst->data, src->size))
116                 return 1;
117         return 0;
118 }
119
120 struct diff_score {
121         int src; /* index in rename_src */
122         int dst; /* index in rename_dst */
123         int score;
124 };
125
126 static int estimate_similarity(struct diff_filespec *src,
127                                struct diff_filespec *dst,
128                                int minimum_score)
129 {
130         /* src points at a file that existed in the original tree (or
131          * optionally a file in the destination tree) and dst points
132          * at a newly created file.  They may be quite similar, in which
133          * case we want to say src is renamed to dst or src is copied into
134          * dst, and then some edit has been applied to dst.
135          *
136          * Compare them and return how similar they are, representing
137          * the score as an integer between 0 and MAX_SCORE.
138          *
139          * When there is an exact match, it is considered a better
140          * match than anything else; the destination does not even
141          * call into this function in that case.
142          */
143         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
144         unsigned long delta_limit;
145         int score;
146
147         /* We deal only with regular files.  Symlink renames are handled
148          * only when they are exact matches --- in other words, no edits
149          * after renaming.
150          */
151         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
152                 return 0;
153
154         max_size = ((src->size > dst->size) ? src->size : dst->size);
155         base_size = ((src->size < dst->size) ? src->size : dst->size);
156         delta_size = max_size - base_size;
157
158         /* We would not consider edits that change the file size so
159          * drastically.  delta_size must be smaller than
160          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
161          *
162          * Note that base_size == 0 case is handled here already
163          * and the final score computation below would not have a
164          * divide-by-zero issue.
165          */
166         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
167                 return 0;
168
169         if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
170                 return 0; /* error but caught downstream */
171
172
173         delta_limit = base_size * (MAX_SCORE-minimum_score) / MAX_SCORE;
174         if (diffcore_count_changes(src->data, src->size,
175                                    dst->data, dst->size,
176                                    &src->cnt_data, &dst->cnt_data,
177                                    delta_limit,
178                                    &src_copied, &literal_added))
179                 return 0;
180
181         /* How similar are they?
182          * what percentage of material in dst are from source?
183          */
184         if (!dst->size)
185                 score = 0; /* should not happen */
186         else
187                 score = src_copied * MAX_SCORE / max_size;
188         return score;
189 }
190
191 static void record_rename_pair(int dst_index, int src_index, int score)
192 {
193         struct diff_filespec *one, *two, *src, *dst;
194         struct diff_filepair *dp;
195
196         if (rename_dst[dst_index].pair)
197                 die("internal error: dst already matched.");
198
199         src = rename_src[src_index].one;
200         one = alloc_filespec(src->path);
201         fill_filespec(one, src->sha1, src->mode);
202
203         dst = rename_dst[dst_index].two;
204         two = alloc_filespec(dst->path);
205         fill_filespec(two, dst->sha1, dst->mode);
206
207         dp = diff_queue(NULL, one, two);
208         dp->renamed_pair = 1;
209         if (!strcmp(src->path, dst->path))
210                 dp->score = rename_src[src_index].score;
211         else
212                 dp->score = score;
213         dp->source_stays = rename_src[src_index].src_path_left;
214         rename_dst[dst_index].pair = dp;
215 }
216
217 /*
218  * We sort the rename similarity matrix with the score, in descending
219  * order (the most similar first).
220  */
221 static int score_compare(const void *a_, const void *b_)
222 {
223         const struct diff_score *a = a_, *b = b_;
224         return b->score - a->score;
225 }
226
227 static int compute_stays(struct diff_queue_struct *q,
228                          struct diff_filespec *one)
229 {
230         int i;
231         for (i = 0; i < q->nr; i++) {
232                 struct diff_filepair *p = q->queue[i];
233                 if (strcmp(one->path, p->two->path))
234                         continue;
235                 if (DIFF_PAIR_RENAME(p)) {
236                         return 0; /* something else is renamed into this */
237                 }
238         }
239         return 1;
240 }
241
242 void diffcore_rename(struct diff_options *options)
243 {
244         int detect_rename = options->detect_rename;
245         int minimum_score = options->rename_score;
246         int rename_limit = options->rename_limit;
247         struct diff_queue_struct *q = &diff_queued_diff;
248         struct diff_queue_struct outq;
249         struct diff_score *mx;
250         int i, j, rename_count, contents_too;
251         int num_create, num_src, dst_cnt;
252
253         if (!minimum_score)
254                 minimum_score = DEFAULT_RENAME_SCORE;
255         rename_count = 0;
256
257         for (i = 0; i < q->nr; i++) {
258                 struct diff_filepair *p = q->queue[i];
259                 if (!DIFF_FILE_VALID(p->one)) {
260                         if (!DIFF_FILE_VALID(p->two))
261                                 continue; /* unmerged */
262                         else if (options->single_follow &&
263                                  strcmp(options->single_follow, p->two->path))
264                                 continue; /* not interested */
265                         else
266                                 locate_rename_dst(p->two, 1);
267                 }
268                 else if (!DIFF_FILE_VALID(p->two)) {
269                         /* If the source is a broken "delete", and
270                          * they did not really want to get broken,
271                          * that means the source actually stays.
272                          */
273                         int stays = (p->broken_pair && !p->score);
274                         register_rename_src(p->one, stays, p->score);
275                 }
276                 else if (detect_rename == DIFF_DETECT_COPY)
277                         register_rename_src(p->one, 1, p->score);
278         }
279         if (rename_dst_nr == 0 || rename_src_nr == 0 ||
280             (0 < rename_limit && rename_limit < rename_dst_nr))
281                 goto cleanup; /* nothing to do */
282
283         /* We really want to cull the candidates list early
284          * with cheap tests in order to avoid doing deltas.
285          * The first round matches up the up-to-date entries,
286          * and then during the second round we try to match
287          * cache-dirty entries as well.
288          */
289         for (contents_too = 0; contents_too < 2; contents_too++) {
290                 for (i = 0; i < rename_dst_nr; i++) {
291                         struct diff_filespec *two = rename_dst[i].two;
292                         if (rename_dst[i].pair)
293                                 continue; /* dealt with an earlier round */
294                         for (j = 0; j < rename_src_nr; j++) {
295                                 struct diff_filespec *one = rename_src[j].one;
296                                 if (!is_exact_match(one, two, contents_too))
297                                         continue;
298                                 record_rename_pair(i, j, MAX_SCORE);
299                                 rename_count++;
300                                 break; /* we are done with this entry */
301                         }
302                 }
303         }
304
305         /* Have we run out the created file pool?  If so we can avoid
306          * doing the delta matrix altogether.
307          */
308         if (rename_count == rename_dst_nr)
309                 goto cleanup;
310
311         if (minimum_score == MAX_SCORE)
312                 goto cleanup;
313
314         num_create = (rename_dst_nr - rename_count);
315         num_src = rename_src_nr;
316         mx = xmalloc(sizeof(*mx) * num_create * num_src);
317         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
318                 int base = dst_cnt * num_src;
319                 struct diff_filespec *two = rename_dst[i].two;
320                 if (rename_dst[i].pair)
321                         continue; /* dealt with exact match already. */
322                 for (j = 0; j < rename_src_nr; j++) {
323                         struct diff_filespec *one = rename_src[j].one;
324                         struct diff_score *m = &mx[base+j];
325                         m->src = j;
326                         m->dst = i;
327                         m->score = estimate_similarity(one, two,
328                                                        minimum_score);
329                 }
330                 /* We do not need the text anymore */
331                 diff_free_filespec_data(two);
332                 dst_cnt++;
333         }
334         /* cost matrix sorted by most to least similar pair */
335         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
336         for (i = 0; i < num_create * num_src; i++) {
337                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
338                 if (dst->pair)
339                         continue; /* already done, either exact or fuzzy. */
340                 if (mx[i].score < minimum_score)
341                         break; /* there is no more usable pair. */
342                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
343                 rename_count++;
344         }
345         free(mx);
346
347  cleanup:
348         /* At this point, we have found some renames and copies and they
349          * are recorded in rename_dst.  The original list is still in *q.
350          */
351         outq.queue = NULL;
352         outq.nr = outq.alloc = 0;
353         for (i = 0; i < q->nr; i++) {
354                 struct diff_filepair *p = q->queue[i];
355                 struct diff_filepair *pair_to_free = NULL;
356
357                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
358                         /*
359                          * Creation
360                          *
361                          * We would output this create record if it has
362                          * not been turned into a rename/copy already.
363                          */
364                         struct diff_rename_dst *dst =
365                                 locate_rename_dst(p->two, 0);
366                         if (dst && dst->pair) {
367                                 diff_q(&outq, dst->pair);
368                                 pair_to_free = p;
369                         }
370                         else
371                                 /* no matching rename/copy source, so
372                                  * record this as a creation.
373                                  */
374                                 diff_q(&outq, p);
375                 }
376                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
377                         /*
378                          * Deletion
379                          *
380                          * We would output this delete record if:
381                          *
382                          * (1) this is a broken delete and the counterpart
383                          *     broken create remains in the output; or
384                          * (2) this is not a broken delete, and rename_dst
385                          *     does not have a rename/copy to move p->one->path
386                          *     out of existence.
387                          *
388                          * Otherwise, the counterpart broken create
389                          * has been turned into a rename-edit; or
390                          * delete did not have a matching create to
391                          * begin with.
392                          */
393                         if (DIFF_PAIR_BROKEN(p)) {
394                                 /* broken delete */
395                                 struct diff_rename_dst *dst =
396                                         locate_rename_dst(p->one, 0);
397                                 if (dst && dst->pair)
398                                         /* counterpart is now rename/copy */
399                                         pair_to_free = p;
400                         }
401                         else {
402                                 for (j = 0; j < rename_dst_nr; j++) {
403                                         if (!rename_dst[j].pair)
404                                                 continue;
405                                         if (strcmp(rename_dst[j].pair->
406                                                    one->path,
407                                                    p->one->path))
408                                                 continue;
409                                         break;
410                                 }
411                                 if (j < rename_dst_nr)
412                                         /* this path remains */
413                                         pair_to_free = p;
414                         }
415
416                         if (pair_to_free)
417                                 ;
418                         else
419                                 diff_q(&outq, p);
420                 }
421                 else if (!diff_unmodified_pair(p))
422                         /* all the usual ones need to be kept */
423                         diff_q(&outq, p);
424                 else
425                         /* no need to keep unmodified pairs */
426                         pair_to_free = p;
427
428                 if (pair_to_free)
429                         diff_free_filepair(pair_to_free);
430         }
431         diff_debug_queue("done copying original", &outq);
432
433         free(q->queue);
434         *q = outq;
435         diff_debug_queue("done collapsing", q);
436
437         /* We need to see which rename source really stays here;
438          * earlier we only checked if the path is left in the result,
439          * but even if a path remains in the result, if that is coming
440          * from copying something else on top of it, then the original
441          * source is lost and does not stay.
442          */
443         for (i = 0; i < q->nr; i++) {
444                 struct diff_filepair *p = q->queue[i];
445                 if (DIFF_PAIR_RENAME(p) && p->source_stays) {
446                         /* If one appears as the target of a rename-copy,
447                          * then mark p->source_stays = 0; otherwise
448                          * leave it as is.
449                          */
450                         p->source_stays = compute_stays(q, p->one);
451                 }
452         }
453
454         for (i = 0; i < rename_dst_nr; i++) {
455                 diff_free_filespec_data(rename_dst[i].two);
456                 free(rename_dst[i].two);
457         }
458
459         free(rename_dst);
460         rename_dst = NULL;
461         rename_dst_nr = rename_dst_alloc = 0;
462         free(rename_src);
463         rename_src = NULL;
464         rename_src_nr = rename_src_alloc = 0;
465         return;
466 }