Merge branch 'js/rebase-recreate-merge'
[git] / blame.c
1 #include "cache.h"
2 #include "refs.h"
3 #include "cache-tree.h"
4 #include "mergesort.h"
5 #include "diff.h"
6 #include "diffcore.h"
7 #include "tag.h"
8 #include "blame.h"
9
10 void blame_origin_decref(struct blame_origin *o)
11 {
12         if (o && --o->refcnt <= 0) {
13                 struct blame_origin *p, *l = NULL;
14                 if (o->previous)
15                         blame_origin_decref(o->previous);
16                 free(o->file.ptr);
17                 /* Should be present exactly once in commit chain */
18                 for (p = o->commit->util; p; l = p, p = p->next) {
19                         if (p == o) {
20                                 if (l)
21                                         l->next = p->next;
22                                 else
23                                         o->commit->util = p->next;
24                                 free(o);
25                                 return;
26                         }
27                 }
28                 die("internal error in blame_origin_decref");
29         }
30 }
31
32 /*
33  * Given a commit and a path in it, create a new origin structure.
34  * The callers that add blame to the scoreboard should use
35  * get_origin() to obtain shared, refcounted copy instead of calling
36  * this function directly.
37  */
38 static struct blame_origin *make_origin(struct commit *commit, const char *path)
39 {
40         struct blame_origin *o;
41         FLEX_ALLOC_STR(o, path, path);
42         o->commit = commit;
43         o->refcnt = 1;
44         o->next = commit->util;
45         commit->util = o;
46         return o;
47 }
48
49 /*
50  * Locate an existing origin or create a new one.
51  * This moves the origin to front position in the commit util list.
52  */
53 static struct blame_origin *get_origin(struct commit *commit, const char *path)
54 {
55         struct blame_origin *o, *l;
56
57         for (o = commit->util, l = NULL; o; l = o, o = o->next) {
58                 if (!strcmp(o->path, path)) {
59                         /* bump to front */
60                         if (l) {
61                                 l->next = o->next;
62                                 o->next = commit->util;
63                                 commit->util = o;
64                         }
65                         return blame_origin_incref(o);
66                 }
67         }
68         return make_origin(commit, path);
69 }
70
71
72
73 static void verify_working_tree_path(struct commit *work_tree, const char *path)
74 {
75         struct commit_list *parents;
76         int pos;
77
78         for (parents = work_tree->parents; parents; parents = parents->next) {
79                 const struct object_id *commit_oid = &parents->item->object.oid;
80                 struct object_id blob_oid;
81                 unsigned mode;
82
83                 if (!get_tree_entry(commit_oid, path, &blob_oid, &mode) &&
84                     oid_object_info(the_repository, &blob_oid, NULL) == OBJ_BLOB)
85                         return;
86         }
87
88         pos = cache_name_pos(path, strlen(path));
89         if (pos >= 0)
90                 ; /* path is in the index */
91         else if (-1 - pos < active_nr &&
92                  !strcmp(active_cache[-1 - pos]->name, path))
93                 ; /* path is in the index, unmerged */
94         else
95                 die("no such path '%s' in HEAD", path);
96 }
97
98 static struct commit_list **append_parent(struct commit_list **tail, const struct object_id *oid)
99 {
100         struct commit *parent;
101
102         parent = lookup_commit_reference(oid);
103         if (!parent)
104                 die("no such commit %s", oid_to_hex(oid));
105         return &commit_list_insert(parent, tail)->next;
106 }
107
108 static void append_merge_parents(struct commit_list **tail)
109 {
110         int merge_head;
111         struct strbuf line = STRBUF_INIT;
112
113         merge_head = open(git_path_merge_head(), O_RDONLY);
114         if (merge_head < 0) {
115                 if (errno == ENOENT)
116                         return;
117                 die("cannot open '%s' for reading", git_path_merge_head());
118         }
119
120         while (!strbuf_getwholeline_fd(&line, merge_head, '\n')) {
121                 struct object_id oid;
122                 if (line.len < GIT_SHA1_HEXSZ || get_oid_hex(line.buf, &oid))
123                         die("unknown line in '%s': %s", git_path_merge_head(), line.buf);
124                 tail = append_parent(tail, &oid);
125         }
126         close(merge_head);
127         strbuf_release(&line);
128 }
129
130 /*
131  * This isn't as simple as passing sb->buf and sb->len, because we
132  * want to transfer ownership of the buffer to the commit (so we
133  * must use detach).
134  */
135 static void set_commit_buffer_from_strbuf(struct commit *c, struct strbuf *sb)
136 {
137         size_t len;
138         void *buf = strbuf_detach(sb, &len);
139         set_commit_buffer(c, buf, len);
140 }
141
142 /*
143  * Prepare a dummy commit that represents the work tree (or staged) item.
144  * Note that annotating work tree item never works in the reverse.
145  */
146 static struct commit *fake_working_tree_commit(struct diff_options *opt,
147                                                const char *path,
148                                                const char *contents_from)
149 {
150         struct commit *commit;
151         struct blame_origin *origin;
152         struct commit_list **parent_tail, *parent;
153         struct object_id head_oid;
154         struct strbuf buf = STRBUF_INIT;
155         const char *ident;
156         time_t now;
157         int size, len;
158         struct cache_entry *ce;
159         unsigned mode;
160         struct strbuf msg = STRBUF_INIT;
161
162         read_cache();
163         time(&now);
164         commit = alloc_commit_node();
165         commit->object.parsed = 1;
166         commit->date = now;
167         parent_tail = &commit->parents;
168
169         if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
170                 die("no such ref: HEAD");
171
172         parent_tail = append_parent(parent_tail, &head_oid);
173         append_merge_parents(parent_tail);
174         verify_working_tree_path(commit, path);
175
176         origin = make_origin(commit, path);
177
178         ident = fmt_ident("Not Committed Yet", "not.committed.yet", NULL, 0);
179         strbuf_addstr(&msg, "tree 0000000000000000000000000000000000000000\n");
180         for (parent = commit->parents; parent; parent = parent->next)
181                 strbuf_addf(&msg, "parent %s\n",
182                             oid_to_hex(&parent->item->object.oid));
183         strbuf_addf(&msg,
184                     "author %s\n"
185                     "committer %s\n\n"
186                     "Version of %s from %s\n",
187                     ident, ident, path,
188                     (!contents_from ? path :
189                      (!strcmp(contents_from, "-") ? "standard input" : contents_from)));
190         set_commit_buffer_from_strbuf(commit, &msg);
191
192         if (!contents_from || strcmp("-", contents_from)) {
193                 struct stat st;
194                 const char *read_from;
195                 char *buf_ptr;
196                 unsigned long buf_len;
197
198                 if (contents_from) {
199                         if (stat(contents_from, &st) < 0)
200                                 die_errno("Cannot stat '%s'", contents_from);
201                         read_from = contents_from;
202                 }
203                 else {
204                         if (lstat(path, &st) < 0)
205                                 die_errno("Cannot lstat '%s'", path);
206                         read_from = path;
207                 }
208                 mode = canon_mode(st.st_mode);
209
210                 switch (st.st_mode & S_IFMT) {
211                 case S_IFREG:
212                         if (opt->flags.allow_textconv &&
213                             textconv_object(read_from, mode, &null_oid, 0, &buf_ptr, &buf_len))
214                                 strbuf_attach(&buf, buf_ptr, buf_len, buf_len + 1);
215                         else if (strbuf_read_file(&buf, read_from, st.st_size) != st.st_size)
216                                 die_errno("cannot open or read '%s'", read_from);
217                         break;
218                 case S_IFLNK:
219                         if (strbuf_readlink(&buf, read_from, st.st_size) < 0)
220                                 die_errno("cannot readlink '%s'", read_from);
221                         break;
222                 default:
223                         die("unsupported file type %s", read_from);
224                 }
225         }
226         else {
227                 /* Reading from stdin */
228                 mode = 0;
229                 if (strbuf_read(&buf, 0, 0) < 0)
230                         die_errno("failed to read from stdin");
231         }
232         convert_to_git(&the_index, path, buf.buf, buf.len, &buf, 0);
233         origin->file.ptr = buf.buf;
234         origin->file.size = buf.len;
235         pretend_object_file(buf.buf, buf.len, OBJ_BLOB, &origin->blob_oid);
236
237         /*
238          * Read the current index, replace the path entry with
239          * origin->blob_sha1 without mucking with its mode or type
240          * bits; we are not going to write this index out -- we just
241          * want to run "diff-index --cached".
242          */
243         discard_cache();
244         read_cache();
245
246         len = strlen(path);
247         if (!mode) {
248                 int pos = cache_name_pos(path, len);
249                 if (0 <= pos)
250                         mode = active_cache[pos]->ce_mode;
251                 else
252                         /* Let's not bother reading from HEAD tree */
253                         mode = S_IFREG | 0644;
254         }
255         size = cache_entry_size(len);
256         ce = xcalloc(1, size);
257         oidcpy(&ce->oid, &origin->blob_oid);
258         memcpy(ce->name, path, len);
259         ce->ce_flags = create_ce_flags(0);
260         ce->ce_namelen = len;
261         ce->ce_mode = create_ce_mode(mode);
262         add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
263
264         cache_tree_invalidate_path(&the_index, path);
265
266         return commit;
267 }
268
269
270
271 static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b,
272                       xdl_emit_hunk_consume_func_t hunk_func, void *cb_data, int xdl_opts)
273 {
274         xpparam_t xpp = {0};
275         xdemitconf_t xecfg = {0};
276         xdemitcb_t ecb = {NULL};
277
278         xpp.flags = xdl_opts;
279         xecfg.hunk_func = hunk_func;
280         ecb.priv = cb_data;
281         return xdi_diff(file_a, file_b, &xpp, &xecfg, &ecb);
282 }
283
284 /*
285  * Given an origin, prepare mmfile_t structure to be used by the
286  * diff machinery
287  */
288 static void fill_origin_blob(struct diff_options *opt,
289                              struct blame_origin *o, mmfile_t *file, int *num_read_blob)
290 {
291         if (!o->file.ptr) {
292                 enum object_type type;
293                 unsigned long file_size;
294
295                 (*num_read_blob)++;
296                 if (opt->flags.allow_textconv &&
297                     textconv_object(o->path, o->mode, &o->blob_oid, 1, &file->ptr, &file_size))
298                         ;
299                 else
300                         file->ptr = read_object_file(&o->blob_oid, &type,
301                                                      &file_size);
302                 file->size = file_size;
303
304                 if (!file->ptr)
305                         die("Cannot read blob %s for path %s",
306                             oid_to_hex(&o->blob_oid),
307                             o->path);
308                 o->file = *file;
309         }
310         else
311                 *file = o->file;
312 }
313
314 static void drop_origin_blob(struct blame_origin *o)
315 {
316         if (o->file.ptr) {
317                 FREE_AND_NULL(o->file.ptr);
318         }
319 }
320
321 /*
322  * Any merge of blames happens on lists of blames that arrived via
323  * different parents in a single suspect.  In this case, we want to
324  * sort according to the suspect line numbers as opposed to the final
325  * image line numbers.  The function body is somewhat longish because
326  * it avoids unnecessary writes.
327  */
328
329 static struct blame_entry *blame_merge(struct blame_entry *list1,
330                                        struct blame_entry *list2)
331 {
332         struct blame_entry *p1 = list1, *p2 = list2,
333                 **tail = &list1;
334
335         if (!p1)
336                 return p2;
337         if (!p2)
338                 return p1;
339
340         if (p1->s_lno <= p2->s_lno) {
341                 do {
342                         tail = &p1->next;
343                         if ((p1 = *tail) == NULL) {
344                                 *tail = p2;
345                                 return list1;
346                         }
347                 } while (p1->s_lno <= p2->s_lno);
348         }
349         for (;;) {
350                 *tail = p2;
351                 do {
352                         tail = &p2->next;
353                         if ((p2 = *tail) == NULL)  {
354                                 *tail = p1;
355                                 return list1;
356                         }
357                 } while (p1->s_lno > p2->s_lno);
358                 *tail = p1;
359                 do {
360                         tail = &p1->next;
361                         if ((p1 = *tail) == NULL) {
362                                 *tail = p2;
363                                 return list1;
364                         }
365                 } while (p1->s_lno <= p2->s_lno);
366         }
367 }
368
369 static void *get_next_blame(const void *p)
370 {
371         return ((struct blame_entry *)p)->next;
372 }
373
374 static void set_next_blame(void *p1, void *p2)
375 {
376         ((struct blame_entry *)p1)->next = p2;
377 }
378
379 /*
380  * Final image line numbers are all different, so we don't need a
381  * three-way comparison here.
382  */
383
384 static int compare_blame_final(const void *p1, const void *p2)
385 {
386         return ((struct blame_entry *)p1)->lno > ((struct blame_entry *)p2)->lno
387                 ? 1 : -1;
388 }
389
390 static int compare_blame_suspect(const void *p1, const void *p2)
391 {
392         const struct blame_entry *s1 = p1, *s2 = p2;
393         /*
394          * to allow for collating suspects, we sort according to the
395          * respective pointer value as the primary sorting criterion.
396          * The actual relation is pretty unimportant as long as it
397          * establishes a total order.  Comparing as integers gives us
398          * that.
399          */
400         if (s1->suspect != s2->suspect)
401                 return (intptr_t)s1->suspect > (intptr_t)s2->suspect ? 1 : -1;
402         if (s1->s_lno == s2->s_lno)
403                 return 0;
404         return s1->s_lno > s2->s_lno ? 1 : -1;
405 }
406
407 void blame_sort_final(struct blame_scoreboard *sb)
408 {
409         sb->ent = llist_mergesort(sb->ent, get_next_blame, set_next_blame,
410                                   compare_blame_final);
411 }
412
413 static int compare_commits_by_reverse_commit_date(const void *a,
414                                                   const void *b,
415                                                   void *c)
416 {
417         return -compare_commits_by_commit_date(a, b, c);
418 }
419
420 /*
421  * For debugging -- origin is refcounted, and this asserts that
422  * we do not underflow.
423  */
424 static void sanity_check_refcnt(struct blame_scoreboard *sb)
425 {
426         int baa = 0;
427         struct blame_entry *ent;
428
429         for (ent = sb->ent; ent; ent = ent->next) {
430                 /* Nobody should have zero or negative refcnt */
431                 if (ent->suspect->refcnt <= 0) {
432                         fprintf(stderr, "%s in %s has negative refcnt %d\n",
433                                 ent->suspect->path,
434                                 oid_to_hex(&ent->suspect->commit->object.oid),
435                                 ent->suspect->refcnt);
436                         baa = 1;
437                 }
438         }
439         if (baa)
440                 sb->on_sanity_fail(sb, baa);
441 }
442
443 /*
444  * If two blame entries that are next to each other came from
445  * contiguous lines in the same origin (i.e. <commit, path> pair),
446  * merge them together.
447  */
448 void blame_coalesce(struct blame_scoreboard *sb)
449 {
450         struct blame_entry *ent, *next;
451
452         for (ent = sb->ent; ent && (next = ent->next); ent = next) {
453                 if (ent->suspect == next->suspect &&
454                     ent->s_lno + ent->num_lines == next->s_lno) {
455                         ent->num_lines += next->num_lines;
456                         ent->next = next->next;
457                         blame_origin_decref(next->suspect);
458                         free(next);
459                         ent->score = 0;
460                         next = ent; /* again */
461                 }
462         }
463
464         if (sb->debug) /* sanity */
465                 sanity_check_refcnt(sb);
466 }
467
468 /*
469  * Merge the given sorted list of blames into a preexisting origin.
470  * If there were no previous blames to that commit, it is entered into
471  * the commit priority queue of the score board.
472  */
473
474 static void queue_blames(struct blame_scoreboard *sb, struct blame_origin *porigin,
475                          struct blame_entry *sorted)
476 {
477         if (porigin->suspects)
478                 porigin->suspects = blame_merge(porigin->suspects, sorted);
479         else {
480                 struct blame_origin *o;
481                 for (o = porigin->commit->util; o; o = o->next) {
482                         if (o->suspects) {
483                                 porigin->suspects = sorted;
484                                 return;
485                         }
486                 }
487                 porigin->suspects = sorted;
488                 prio_queue_put(&sb->commits, porigin->commit);
489         }
490 }
491
492 /*
493  * Fill the blob_sha1 field of an origin if it hasn't, so that later
494  * call to fill_origin_blob() can use it to locate the data.  blob_sha1
495  * for an origin is also used to pass the blame for the entire file to
496  * the parent to detect the case where a child's blob is identical to
497  * that of its parent's.
498  *
499  * This also fills origin->mode for corresponding tree path.
500  */
501 static int fill_blob_sha1_and_mode(struct blame_origin *origin)
502 {
503         if (!is_null_oid(&origin->blob_oid))
504                 return 0;
505         if (get_tree_entry(&origin->commit->object.oid, origin->path, &origin->blob_oid, &origin->mode))
506                 goto error_out;
507         if (oid_object_info(the_repository, &origin->blob_oid, NULL) != OBJ_BLOB)
508                 goto error_out;
509         return 0;
510  error_out:
511         oidclr(&origin->blob_oid);
512         origin->mode = S_IFINVALID;
513         return -1;
514 }
515
516 /*
517  * We have an origin -- check if the same path exists in the
518  * parent and return an origin structure to represent it.
519  */
520 static struct blame_origin *find_origin(struct commit *parent,
521                                   struct blame_origin *origin)
522 {
523         struct blame_origin *porigin;
524         struct diff_options diff_opts;
525         const char *paths[2];
526
527         /* First check any existing origins */
528         for (porigin = parent->util; porigin; porigin = porigin->next)
529                 if (!strcmp(porigin->path, origin->path)) {
530                         /*
531                          * The same path between origin and its parent
532                          * without renaming -- the most common case.
533                          */
534                         return blame_origin_incref (porigin);
535                 }
536
537         /* See if the origin->path is different between parent
538          * and origin first.  Most of the time they are the
539          * same and diff-tree is fairly efficient about this.
540          */
541         diff_setup(&diff_opts);
542         diff_opts.flags.recursive = 1;
543         diff_opts.detect_rename = 0;
544         diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
545         paths[0] = origin->path;
546         paths[1] = NULL;
547
548         parse_pathspec(&diff_opts.pathspec,
549                        PATHSPEC_ALL_MAGIC & ~PATHSPEC_LITERAL,
550                        PATHSPEC_LITERAL_PATH, "", paths);
551         diff_setup_done(&diff_opts);
552
553         if (is_null_oid(&origin->commit->object.oid))
554                 do_diff_cache(get_commit_tree_oid(parent), &diff_opts);
555         else
556                 diff_tree_oid(get_commit_tree_oid(parent),
557                               get_commit_tree_oid(origin->commit),
558                               "", &diff_opts);
559         diffcore_std(&diff_opts);
560
561         if (!diff_queued_diff.nr) {
562                 /* The path is the same as parent */
563                 porigin = get_origin(parent, origin->path);
564                 oidcpy(&porigin->blob_oid, &origin->blob_oid);
565                 porigin->mode = origin->mode;
566         } else {
567                 /*
568                  * Since origin->path is a pathspec, if the parent
569                  * commit had it as a directory, we will see a whole
570                  * bunch of deletion of files in the directory that we
571                  * do not care about.
572                  */
573                 int i;
574                 struct diff_filepair *p = NULL;
575                 for (i = 0; i < diff_queued_diff.nr; i++) {
576                         const char *name;
577                         p = diff_queued_diff.queue[i];
578                         name = p->one->path ? p->one->path : p->two->path;
579                         if (!strcmp(name, origin->path))
580                                 break;
581                 }
582                 if (!p)
583                         die("internal error in blame::find_origin");
584                 switch (p->status) {
585                 default:
586                         die("internal error in blame::find_origin (%c)",
587                             p->status);
588                 case 'M':
589                         porigin = get_origin(parent, origin->path);
590                         oidcpy(&porigin->blob_oid, &p->one->oid);
591                         porigin->mode = p->one->mode;
592                         break;
593                 case 'A':
594                 case 'T':
595                         /* Did not exist in parent, or type changed */
596                         break;
597                 }
598         }
599         diff_flush(&diff_opts);
600         clear_pathspec(&diff_opts.pathspec);
601         return porigin;
602 }
603
604 /*
605  * We have an origin -- find the path that corresponds to it in its
606  * parent and return an origin structure to represent it.
607  */
608 static struct blame_origin *find_rename(struct commit *parent,
609                                   struct blame_origin *origin)
610 {
611         struct blame_origin *porigin = NULL;
612         struct diff_options diff_opts;
613         int i;
614
615         diff_setup(&diff_opts);
616         diff_opts.flags.recursive = 1;
617         diff_opts.detect_rename = DIFF_DETECT_RENAME;
618         diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
619         diff_opts.single_follow = origin->path;
620         diff_setup_done(&diff_opts);
621
622         if (is_null_oid(&origin->commit->object.oid))
623                 do_diff_cache(get_commit_tree_oid(parent), &diff_opts);
624         else
625                 diff_tree_oid(get_commit_tree_oid(parent),
626                               get_commit_tree_oid(origin->commit),
627                               "", &diff_opts);
628         diffcore_std(&diff_opts);
629
630         for (i = 0; i < diff_queued_diff.nr; i++) {
631                 struct diff_filepair *p = diff_queued_diff.queue[i];
632                 if ((p->status == 'R' || p->status == 'C') &&
633                     !strcmp(p->two->path, origin->path)) {
634                         porigin = get_origin(parent, p->one->path);
635                         oidcpy(&porigin->blob_oid, &p->one->oid);
636                         porigin->mode = p->one->mode;
637                         break;
638                 }
639         }
640         diff_flush(&diff_opts);
641         clear_pathspec(&diff_opts.pathspec);
642         return porigin;
643 }
644
645 /*
646  * Append a new blame entry to a given output queue.
647  */
648 static void add_blame_entry(struct blame_entry ***queue,
649                             const struct blame_entry *src)
650 {
651         struct blame_entry *e = xmalloc(sizeof(*e));
652         memcpy(e, src, sizeof(*e));
653         blame_origin_incref(e->suspect);
654
655         e->next = **queue;
656         **queue = e;
657         *queue = &e->next;
658 }
659
660 /*
661  * src typically is on-stack; we want to copy the information in it to
662  * a malloced blame_entry that gets added to the given queue.  The
663  * origin of dst loses a refcnt.
664  */
665 static void dup_entry(struct blame_entry ***queue,
666                       struct blame_entry *dst, struct blame_entry *src)
667 {
668         blame_origin_incref(src->suspect);
669         blame_origin_decref(dst->suspect);
670         memcpy(dst, src, sizeof(*src));
671         dst->next = **queue;
672         **queue = dst;
673         *queue = &dst->next;
674 }
675
676 const char *blame_nth_line(struct blame_scoreboard *sb, long lno)
677 {
678         return sb->final_buf + sb->lineno[lno];
679 }
680
681 /*
682  * It is known that lines between tlno to same came from parent, and e
683  * has an overlap with that range.  it also is known that parent's
684  * line plno corresponds to e's line tlno.
685  *
686  *                <---- e ----->
687  *                   <------>
688  *                   <------------>
689  *             <------------>
690  *             <------------------>
691  *
692  * Split e into potentially three parts; before this chunk, the chunk
693  * to be blamed for the parent, and after that portion.
694  */
695 static void split_overlap(struct blame_entry *split,
696                           struct blame_entry *e,
697                           int tlno, int plno, int same,
698                           struct blame_origin *parent)
699 {
700         int chunk_end_lno;
701         memset(split, 0, sizeof(struct blame_entry [3]));
702
703         if (e->s_lno < tlno) {
704                 /* there is a pre-chunk part not blamed on parent */
705                 split[0].suspect = blame_origin_incref(e->suspect);
706                 split[0].lno = e->lno;
707                 split[0].s_lno = e->s_lno;
708                 split[0].num_lines = tlno - e->s_lno;
709                 split[1].lno = e->lno + tlno - e->s_lno;
710                 split[1].s_lno = plno;
711         }
712         else {
713                 split[1].lno = e->lno;
714                 split[1].s_lno = plno + (e->s_lno - tlno);
715         }
716
717         if (same < e->s_lno + e->num_lines) {
718                 /* there is a post-chunk part not blamed on parent */
719                 split[2].suspect = blame_origin_incref(e->suspect);
720                 split[2].lno = e->lno + (same - e->s_lno);
721                 split[2].s_lno = e->s_lno + (same - e->s_lno);
722                 split[2].num_lines = e->s_lno + e->num_lines - same;
723                 chunk_end_lno = split[2].lno;
724         }
725         else
726                 chunk_end_lno = e->lno + e->num_lines;
727         split[1].num_lines = chunk_end_lno - split[1].lno;
728
729         /*
730          * if it turns out there is nothing to blame the parent for,
731          * forget about the splitting.  !split[1].suspect signals this.
732          */
733         if (split[1].num_lines < 1)
734                 return;
735         split[1].suspect = blame_origin_incref(parent);
736 }
737
738 /*
739  * split_overlap() divided an existing blame e into up to three parts
740  * in split.  Any assigned blame is moved to queue to
741  * reflect the split.
742  */
743 static void split_blame(struct blame_entry ***blamed,
744                         struct blame_entry ***unblamed,
745                         struct blame_entry *split,
746                         struct blame_entry *e)
747 {
748         if (split[0].suspect && split[2].suspect) {
749                 /* The first part (reuse storage for the existing entry e) */
750                 dup_entry(unblamed, e, &split[0]);
751
752                 /* The last part -- me */
753                 add_blame_entry(unblamed, &split[2]);
754
755                 /* ... and the middle part -- parent */
756                 add_blame_entry(blamed, &split[1]);
757         }
758         else if (!split[0].suspect && !split[2].suspect)
759                 /*
760                  * The parent covers the entire area; reuse storage for
761                  * e and replace it with the parent.
762                  */
763                 dup_entry(blamed, e, &split[1]);
764         else if (split[0].suspect) {
765                 /* me and then parent */
766                 dup_entry(unblamed, e, &split[0]);
767                 add_blame_entry(blamed, &split[1]);
768         }
769         else {
770                 /* parent and then me */
771                 dup_entry(blamed, e, &split[1]);
772                 add_blame_entry(unblamed, &split[2]);
773         }
774 }
775
776 /*
777  * After splitting the blame, the origins used by the
778  * on-stack blame_entry should lose one refcnt each.
779  */
780 static void decref_split(struct blame_entry *split)
781 {
782         int i;
783
784         for (i = 0; i < 3; i++)
785                 blame_origin_decref(split[i].suspect);
786 }
787
788 /*
789  * reverse_blame reverses the list given in head, appending tail.
790  * That allows us to build lists in reverse order, then reverse them
791  * afterwards.  This can be faster than building the list in proper
792  * order right away.  The reason is that building in proper order
793  * requires writing a link in the _previous_ element, while building
794  * in reverse order just requires placing the list head into the
795  * _current_ element.
796  */
797
798 static struct blame_entry *reverse_blame(struct blame_entry *head,
799                                          struct blame_entry *tail)
800 {
801         while (head) {
802                 struct blame_entry *next = head->next;
803                 head->next = tail;
804                 tail = head;
805                 head = next;
806         }
807         return tail;
808 }
809
810 /*
811  * Process one hunk from the patch between the current suspect for
812  * blame_entry e and its parent.  This first blames any unfinished
813  * entries before the chunk (which is where target and parent start
814  * differing) on the parent, and then splits blame entries at the
815  * start and at the end of the difference region.  Since use of -M and
816  * -C options may lead to overlapping/duplicate source line number
817  * ranges, all we can rely on from sorting/merging is the order of the
818  * first suspect line number.
819  */
820 static void blame_chunk(struct blame_entry ***dstq, struct blame_entry ***srcq,
821                         int tlno, int offset, int same,
822                         struct blame_origin *parent)
823 {
824         struct blame_entry *e = **srcq;
825         struct blame_entry *samep = NULL, *diffp = NULL;
826
827         while (e && e->s_lno < tlno) {
828                 struct blame_entry *next = e->next;
829                 /*
830                  * current record starts before differing portion.  If
831                  * it reaches into it, we need to split it up and
832                  * examine the second part separately.
833                  */
834                 if (e->s_lno + e->num_lines > tlno) {
835                         /* Move second half to a new record */
836                         int len = tlno - e->s_lno;
837                         struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
838                         n->suspect = e->suspect;
839                         n->lno = e->lno + len;
840                         n->s_lno = e->s_lno + len;
841                         n->num_lines = e->num_lines - len;
842                         e->num_lines = len;
843                         e->score = 0;
844                         /* Push new record to diffp */
845                         n->next = diffp;
846                         diffp = n;
847                 } else
848                         blame_origin_decref(e->suspect);
849                 /* Pass blame for everything before the differing
850                  * chunk to the parent */
851                 e->suspect = blame_origin_incref(parent);
852                 e->s_lno += offset;
853                 e->next = samep;
854                 samep = e;
855                 e = next;
856         }
857         /*
858          * As we don't know how much of a common stretch after this
859          * diff will occur, the currently blamed parts are all that we
860          * can assign to the parent for now.
861          */
862
863         if (samep) {
864                 **dstq = reverse_blame(samep, **dstq);
865                 *dstq = &samep->next;
866         }
867         /*
868          * Prepend the split off portions: everything after e starts
869          * after the blameable portion.
870          */
871         e = reverse_blame(diffp, e);
872
873         /*
874          * Now retain records on the target while parts are different
875          * from the parent.
876          */
877         samep = NULL;
878         diffp = NULL;
879         while (e && e->s_lno < same) {
880                 struct blame_entry *next = e->next;
881
882                 /*
883                  * If current record extends into sameness, need to split.
884                  */
885                 if (e->s_lno + e->num_lines > same) {
886                         /*
887                          * Move second half to a new record to be
888                          * processed by later chunks
889                          */
890                         int len = same - e->s_lno;
891                         struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
892                         n->suspect = blame_origin_incref(e->suspect);
893                         n->lno = e->lno + len;
894                         n->s_lno = e->s_lno + len;
895                         n->num_lines = e->num_lines - len;
896                         e->num_lines = len;
897                         e->score = 0;
898                         /* Push new record to samep */
899                         n->next = samep;
900                         samep = n;
901                 }
902                 e->next = diffp;
903                 diffp = e;
904                 e = next;
905         }
906         **srcq = reverse_blame(diffp, reverse_blame(samep, e));
907         /* Move across elements that are in the unblamable portion */
908         if (diffp)
909                 *srcq = &diffp->next;
910 }
911
912 struct blame_chunk_cb_data {
913         struct blame_origin *parent;
914         long offset;
915         struct blame_entry **dstq;
916         struct blame_entry **srcq;
917 };
918
919 /* diff chunks are from parent to target */
920 static int blame_chunk_cb(long start_a, long count_a,
921                           long start_b, long count_b, void *data)
922 {
923         struct blame_chunk_cb_data *d = data;
924         if (start_a - start_b != d->offset)
925                 die("internal error in blame::blame_chunk_cb");
926         blame_chunk(&d->dstq, &d->srcq, start_b, start_a - start_b,
927                     start_b + count_b, d->parent);
928         d->offset = start_a + count_a - (start_b + count_b);
929         return 0;
930 }
931
932 /*
933  * We are looking at the origin 'target' and aiming to pass blame
934  * for the lines it is suspected to its parent.  Run diff to find
935  * which lines came from parent and pass blame for them.
936  */
937 static void pass_blame_to_parent(struct blame_scoreboard *sb,
938                                  struct blame_origin *target,
939                                  struct blame_origin *parent)
940 {
941         mmfile_t file_p, file_o;
942         struct blame_chunk_cb_data d;
943         struct blame_entry *newdest = NULL;
944
945         if (!target->suspects)
946                 return; /* nothing remains for this target */
947
948         d.parent = parent;
949         d.offset = 0;
950         d.dstq = &newdest; d.srcq = &target->suspects;
951
952         fill_origin_blob(&sb->revs->diffopt, parent, &file_p, &sb->num_read_blob);
953         fill_origin_blob(&sb->revs->diffopt, target, &file_o, &sb->num_read_blob);
954         sb->num_get_patch++;
955
956         if (diff_hunks(&file_p, &file_o, blame_chunk_cb, &d, sb->xdl_opts))
957                 die("unable to generate diff (%s -> %s)",
958                     oid_to_hex(&parent->commit->object.oid),
959                     oid_to_hex(&target->commit->object.oid));
960         /* The rest are the same as the parent */
961         blame_chunk(&d.dstq, &d.srcq, INT_MAX, d.offset, INT_MAX, parent);
962         *d.dstq = NULL;
963         queue_blames(sb, parent, newdest);
964
965         return;
966 }
967
968 /*
969  * The lines in blame_entry after splitting blames many times can become
970  * very small and trivial, and at some point it becomes pointless to
971  * blame the parents.  E.g. "\t\t}\n\t}\n\n" appears everywhere in any
972  * ordinary C program, and it is not worth to say it was copied from
973  * totally unrelated file in the parent.
974  *
975  * Compute how trivial the lines in the blame_entry are.
976  */
977 unsigned blame_entry_score(struct blame_scoreboard *sb, struct blame_entry *e)
978 {
979         unsigned score;
980         const char *cp, *ep;
981
982         if (e->score)
983                 return e->score;
984
985         score = 1;
986         cp = blame_nth_line(sb, e->lno);
987         ep = blame_nth_line(sb, e->lno + e->num_lines);
988         while (cp < ep) {
989                 unsigned ch = *((unsigned char *)cp);
990                 if (isalnum(ch))
991                         score++;
992                 cp++;
993         }
994         e->score = score;
995         return score;
996 }
997
998 /*
999  * best_so_far[] and potential[] are both a split of an existing blame_entry
1000  * that passes blame to the parent.  Maintain best_so_far the best split so
1001  * far, by comparing potential and best_so_far and copying potential into
1002  * bst_so_far as needed.
1003  */
1004 static void copy_split_if_better(struct blame_scoreboard *sb,
1005                                  struct blame_entry *best_so_far,
1006                                  struct blame_entry *potential)
1007 {
1008         int i;
1009
1010         if (!potential[1].suspect)
1011                 return;
1012         if (best_so_far[1].suspect) {
1013                 if (blame_entry_score(sb, &potential[1]) <
1014                     blame_entry_score(sb, &best_so_far[1]))
1015                         return;
1016         }
1017
1018         for (i = 0; i < 3; i++)
1019                 blame_origin_incref(potential[i].suspect);
1020         decref_split(best_so_far);
1021         memcpy(best_so_far, potential, sizeof(struct blame_entry[3]));
1022 }
1023
1024 /*
1025  * We are looking at a part of the final image represented by
1026  * ent (tlno and same are offset by ent->s_lno).
1027  * tlno is where we are looking at in the final image.
1028  * up to (but not including) same match preimage.
1029  * plno is where we are looking at in the preimage.
1030  *
1031  * <-------------- final image ---------------------->
1032  *       <------ent------>
1033  *         ^tlno ^same
1034  *    <---------preimage----->
1035  *         ^plno
1036  *
1037  * All line numbers are 0-based.
1038  */
1039 static void handle_split(struct blame_scoreboard *sb,
1040                          struct blame_entry *ent,
1041                          int tlno, int plno, int same,
1042                          struct blame_origin *parent,
1043                          struct blame_entry *split)
1044 {
1045         if (ent->num_lines <= tlno)
1046                 return;
1047         if (tlno < same) {
1048                 struct blame_entry potential[3];
1049                 tlno += ent->s_lno;
1050                 same += ent->s_lno;
1051                 split_overlap(potential, ent, tlno, plno, same, parent);
1052                 copy_split_if_better(sb, split, potential);
1053                 decref_split(potential);
1054         }
1055 }
1056
1057 struct handle_split_cb_data {
1058         struct blame_scoreboard *sb;
1059         struct blame_entry *ent;
1060         struct blame_origin *parent;
1061         struct blame_entry *split;
1062         long plno;
1063         long tlno;
1064 };
1065
1066 static int handle_split_cb(long start_a, long count_a,
1067                            long start_b, long count_b, void *data)
1068 {
1069         struct handle_split_cb_data *d = data;
1070         handle_split(d->sb, d->ent, d->tlno, d->plno, start_b, d->parent,
1071                      d->split);
1072         d->plno = start_a + count_a;
1073         d->tlno = start_b + count_b;
1074         return 0;
1075 }
1076
1077 /*
1078  * Find the lines from parent that are the same as ent so that
1079  * we can pass blames to it.  file_p has the blob contents for
1080  * the parent.
1081  */
1082 static void find_copy_in_blob(struct blame_scoreboard *sb,
1083                               struct blame_entry *ent,
1084                               struct blame_origin *parent,
1085                               struct blame_entry *split,
1086                               mmfile_t *file_p)
1087 {
1088         const char *cp;
1089         mmfile_t file_o;
1090         struct handle_split_cb_data d;
1091
1092         memset(&d, 0, sizeof(d));
1093         d.sb = sb; d.ent = ent; d.parent = parent; d.split = split;
1094         /*
1095          * Prepare mmfile that contains only the lines in ent.
1096          */
1097         cp = blame_nth_line(sb, ent->lno);
1098         file_o.ptr = (char *) cp;
1099         file_o.size = blame_nth_line(sb, ent->lno + ent->num_lines) - cp;
1100
1101         /*
1102          * file_o is a part of final image we are annotating.
1103          * file_p partially may match that image.
1104          */
1105         memset(split, 0, sizeof(struct blame_entry [3]));
1106         if (diff_hunks(file_p, &file_o, handle_split_cb, &d, sb->xdl_opts))
1107                 die("unable to generate diff (%s)",
1108                     oid_to_hex(&parent->commit->object.oid));
1109         /* remainder, if any, all match the preimage */
1110         handle_split(sb, ent, d.tlno, d.plno, ent->num_lines, parent, split);
1111 }
1112
1113 /* Move all blame entries from list *source that have a score smaller
1114  * than score_min to the front of list *small.
1115  * Returns a pointer to the link pointing to the old head of the small list.
1116  */
1117
1118 static struct blame_entry **filter_small(struct blame_scoreboard *sb,
1119                                          struct blame_entry **small,
1120                                          struct blame_entry **source,
1121                                          unsigned score_min)
1122 {
1123         struct blame_entry *p = *source;
1124         struct blame_entry *oldsmall = *small;
1125         while (p) {
1126                 if (blame_entry_score(sb, p) <= score_min) {
1127                         *small = p;
1128                         small = &p->next;
1129                         p = *small;
1130                 } else {
1131                         *source = p;
1132                         source = &p->next;
1133                         p = *source;
1134                 }
1135         }
1136         *small = oldsmall;
1137         *source = NULL;
1138         return small;
1139 }
1140
1141 /*
1142  * See if lines currently target is suspected for can be attributed to
1143  * parent.
1144  */
1145 static void find_move_in_parent(struct blame_scoreboard *sb,
1146                                 struct blame_entry ***blamed,
1147                                 struct blame_entry **toosmall,
1148                                 struct blame_origin *target,
1149                                 struct blame_origin *parent)
1150 {
1151         struct blame_entry *e, split[3];
1152         struct blame_entry *unblamed = target->suspects;
1153         struct blame_entry *leftover = NULL;
1154         mmfile_t file_p;
1155
1156         if (!unblamed)
1157                 return; /* nothing remains for this target */
1158
1159         fill_origin_blob(&sb->revs->diffopt, parent, &file_p, &sb->num_read_blob);
1160         if (!file_p.ptr)
1161                 return;
1162
1163         /* At each iteration, unblamed has a NULL-terminated list of
1164          * entries that have not yet been tested for blame.  leftover
1165          * contains the reversed list of entries that have been tested
1166          * without being assignable to the parent.
1167          */
1168         do {
1169                 struct blame_entry **unblamedtail = &unblamed;
1170                 struct blame_entry *next;
1171                 for (e = unblamed; e; e = next) {
1172                         next = e->next;
1173                         find_copy_in_blob(sb, e, parent, split, &file_p);
1174                         if (split[1].suspect &&
1175                             sb->move_score < blame_entry_score(sb, &split[1])) {
1176                                 split_blame(blamed, &unblamedtail, split, e);
1177                         } else {
1178                                 e->next = leftover;
1179                                 leftover = e;
1180                         }
1181                         decref_split(split);
1182                 }
1183                 *unblamedtail = NULL;
1184                 toosmall = filter_small(sb, toosmall, &unblamed, sb->move_score);
1185         } while (unblamed);
1186         target->suspects = reverse_blame(leftover, NULL);
1187 }
1188
1189 struct blame_list {
1190         struct blame_entry *ent;
1191         struct blame_entry split[3];
1192 };
1193
1194 /*
1195  * Count the number of entries the target is suspected for,
1196  * and prepare a list of entry and the best split.
1197  */
1198 static struct blame_list *setup_blame_list(struct blame_entry *unblamed,
1199                                            int *num_ents_p)
1200 {
1201         struct blame_entry *e;
1202         int num_ents, i;
1203         struct blame_list *blame_list = NULL;
1204
1205         for (e = unblamed, num_ents = 0; e; e = e->next)
1206                 num_ents++;
1207         if (num_ents) {
1208                 blame_list = xcalloc(num_ents, sizeof(struct blame_list));
1209                 for (e = unblamed, i = 0; e; e = e->next)
1210                         blame_list[i++].ent = e;
1211         }
1212         *num_ents_p = num_ents;
1213         return blame_list;
1214 }
1215
1216 /*
1217  * For lines target is suspected for, see if we can find code movement
1218  * across file boundary from the parent commit.  porigin is the path
1219  * in the parent we already tried.
1220  */
1221 static void find_copy_in_parent(struct blame_scoreboard *sb,
1222                                 struct blame_entry ***blamed,
1223                                 struct blame_entry **toosmall,
1224                                 struct blame_origin *target,
1225                                 struct commit *parent,
1226                                 struct blame_origin *porigin,
1227                                 int opt)
1228 {
1229         struct diff_options diff_opts;
1230         int i, j;
1231         struct blame_list *blame_list;
1232         int num_ents;
1233         struct blame_entry *unblamed = target->suspects;
1234         struct blame_entry *leftover = NULL;
1235
1236         if (!unblamed)
1237                 return; /* nothing remains for this target */
1238
1239         diff_setup(&diff_opts);
1240         diff_opts.flags.recursive = 1;
1241         diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
1242
1243         diff_setup_done(&diff_opts);
1244
1245         /* Try "find copies harder" on new path if requested;
1246          * we do not want to use diffcore_rename() actually to
1247          * match things up; find_copies_harder is set only to
1248          * force diff_tree_oid() to feed all filepairs to diff_queue,
1249          * and this code needs to be after diff_setup_done(), which
1250          * usually makes find-copies-harder imply copy detection.
1251          */
1252         if ((opt & PICKAXE_BLAME_COPY_HARDEST)
1253             || ((opt & PICKAXE_BLAME_COPY_HARDER)
1254                 && (!porigin || strcmp(target->path, porigin->path))))
1255                 diff_opts.flags.find_copies_harder = 1;
1256
1257         if (is_null_oid(&target->commit->object.oid))
1258                 do_diff_cache(get_commit_tree_oid(parent), &diff_opts);
1259         else
1260                 diff_tree_oid(get_commit_tree_oid(parent),
1261                               get_commit_tree_oid(target->commit),
1262                               "", &diff_opts);
1263
1264         if (!diff_opts.flags.find_copies_harder)
1265                 diffcore_std(&diff_opts);
1266
1267         do {
1268                 struct blame_entry **unblamedtail = &unblamed;
1269                 blame_list = setup_blame_list(unblamed, &num_ents);
1270
1271                 for (i = 0; i < diff_queued_diff.nr; i++) {
1272                         struct diff_filepair *p = diff_queued_diff.queue[i];
1273                         struct blame_origin *norigin;
1274                         mmfile_t file_p;
1275                         struct blame_entry potential[3];
1276
1277                         if (!DIFF_FILE_VALID(p->one))
1278                                 continue; /* does not exist in parent */
1279                         if (S_ISGITLINK(p->one->mode))
1280                                 continue; /* ignore git links */
1281                         if (porigin && !strcmp(p->one->path, porigin->path))
1282                                 /* find_move already dealt with this path */
1283                                 continue;
1284
1285                         norigin = get_origin(parent, p->one->path);
1286                         oidcpy(&norigin->blob_oid, &p->one->oid);
1287                         norigin->mode = p->one->mode;
1288                         fill_origin_blob(&sb->revs->diffopt, norigin, &file_p, &sb->num_read_blob);
1289                         if (!file_p.ptr)
1290                                 continue;
1291
1292                         for (j = 0; j < num_ents; j++) {
1293                                 find_copy_in_blob(sb, blame_list[j].ent,
1294                                                   norigin, potential, &file_p);
1295                                 copy_split_if_better(sb, blame_list[j].split,
1296                                                      potential);
1297                                 decref_split(potential);
1298                         }
1299                         blame_origin_decref(norigin);
1300                 }
1301
1302                 for (j = 0; j < num_ents; j++) {
1303                         struct blame_entry *split = blame_list[j].split;
1304                         if (split[1].suspect &&
1305                             sb->copy_score < blame_entry_score(sb, &split[1])) {
1306                                 split_blame(blamed, &unblamedtail, split,
1307                                             blame_list[j].ent);
1308                         } else {
1309                                 blame_list[j].ent->next = leftover;
1310                                 leftover = blame_list[j].ent;
1311                         }
1312                         decref_split(split);
1313                 }
1314                 free(blame_list);
1315                 *unblamedtail = NULL;
1316                 toosmall = filter_small(sb, toosmall, &unblamed, sb->copy_score);
1317         } while (unblamed);
1318         target->suspects = reverse_blame(leftover, NULL);
1319         diff_flush(&diff_opts);
1320         clear_pathspec(&diff_opts.pathspec);
1321 }
1322
1323 /*
1324  * The blobs of origin and porigin exactly match, so everything
1325  * origin is suspected for can be blamed on the parent.
1326  */
1327 static void pass_whole_blame(struct blame_scoreboard *sb,
1328                              struct blame_origin *origin, struct blame_origin *porigin)
1329 {
1330         struct blame_entry *e, *suspects;
1331
1332         if (!porigin->file.ptr && origin->file.ptr) {
1333                 /* Steal its file */
1334                 porigin->file = origin->file;
1335                 origin->file.ptr = NULL;
1336         }
1337         suspects = origin->suspects;
1338         origin->suspects = NULL;
1339         for (e = suspects; e; e = e->next) {
1340                 blame_origin_incref(porigin);
1341                 blame_origin_decref(e->suspect);
1342                 e->suspect = porigin;
1343         }
1344         queue_blames(sb, porigin, suspects);
1345 }
1346
1347 /*
1348  * We pass blame from the current commit to its parents.  We keep saying
1349  * "parent" (and "porigin"), but what we mean is to find scapegoat to
1350  * exonerate ourselves.
1351  */
1352 static struct commit_list *first_scapegoat(struct rev_info *revs, struct commit *commit,
1353                                         int reverse)
1354 {
1355         if (!reverse) {
1356                 if (revs->first_parent_only &&
1357                     commit->parents &&
1358                     commit->parents->next) {
1359                         free_commit_list(commit->parents->next);
1360                         commit->parents->next = NULL;
1361                 }
1362                 return commit->parents;
1363         }
1364         return lookup_decoration(&revs->children, &commit->object);
1365 }
1366
1367 static int num_scapegoats(struct rev_info *revs, struct commit *commit, int reverse)
1368 {
1369         struct commit_list *l = first_scapegoat(revs, commit, reverse);
1370         return commit_list_count(l);
1371 }
1372
1373 /* Distribute collected unsorted blames to the respected sorted lists
1374  * in the various origins.
1375  */
1376 static void distribute_blame(struct blame_scoreboard *sb, struct blame_entry *blamed)
1377 {
1378         blamed = llist_mergesort(blamed, get_next_blame, set_next_blame,
1379                                  compare_blame_suspect);
1380         while (blamed)
1381         {
1382                 struct blame_origin *porigin = blamed->suspect;
1383                 struct blame_entry *suspects = NULL;
1384                 do {
1385                         struct blame_entry *next = blamed->next;
1386                         blamed->next = suspects;
1387                         suspects = blamed;
1388                         blamed = next;
1389                 } while (blamed && blamed->suspect == porigin);
1390                 suspects = reverse_blame(suspects, NULL);
1391                 queue_blames(sb, porigin, suspects);
1392         }
1393 }
1394
1395 #define MAXSG 16
1396
1397 static void pass_blame(struct blame_scoreboard *sb, struct blame_origin *origin, int opt)
1398 {
1399         struct rev_info *revs = sb->revs;
1400         int i, pass, num_sg;
1401         struct commit *commit = origin->commit;
1402         struct commit_list *sg;
1403         struct blame_origin *sg_buf[MAXSG];
1404         struct blame_origin *porigin, **sg_origin = sg_buf;
1405         struct blame_entry *toosmall = NULL;
1406         struct blame_entry *blames, **blametail = &blames;
1407
1408         num_sg = num_scapegoats(revs, commit, sb->reverse);
1409         if (!num_sg)
1410                 goto finish;
1411         else if (num_sg < ARRAY_SIZE(sg_buf))
1412                 memset(sg_buf, 0, sizeof(sg_buf));
1413         else
1414                 sg_origin = xcalloc(num_sg, sizeof(*sg_origin));
1415
1416         /*
1417          * The first pass looks for unrenamed path to optimize for
1418          * common cases, then we look for renames in the second pass.
1419          */
1420         for (pass = 0; pass < 2 - sb->no_whole_file_rename; pass++) {
1421                 struct blame_origin *(*find)(struct commit *, struct blame_origin *);
1422                 find = pass ? find_rename : find_origin;
1423
1424                 for (i = 0, sg = first_scapegoat(revs, commit, sb->reverse);
1425                      i < num_sg && sg;
1426                      sg = sg->next, i++) {
1427                         struct commit *p = sg->item;
1428                         int j, same;
1429
1430                         if (sg_origin[i])
1431                                 continue;
1432                         if (parse_commit(p))
1433                                 continue;
1434                         porigin = find(p, origin);
1435                         if (!porigin)
1436                                 continue;
1437                         if (!oidcmp(&porigin->blob_oid, &origin->blob_oid)) {
1438                                 pass_whole_blame(sb, origin, porigin);
1439                                 blame_origin_decref(porigin);
1440                                 goto finish;
1441                         }
1442                         for (j = same = 0; j < i; j++)
1443                                 if (sg_origin[j] &&
1444                                     !oidcmp(&sg_origin[j]->blob_oid, &porigin->blob_oid)) {
1445                                         same = 1;
1446                                         break;
1447                                 }
1448                         if (!same)
1449                                 sg_origin[i] = porigin;
1450                         else
1451                                 blame_origin_decref(porigin);
1452                 }
1453         }
1454
1455         sb->num_commits++;
1456         for (i = 0, sg = first_scapegoat(revs, commit, sb->reverse);
1457              i < num_sg && sg;
1458              sg = sg->next, i++) {
1459                 struct blame_origin *porigin = sg_origin[i];
1460                 if (!porigin)
1461                         continue;
1462                 if (!origin->previous) {
1463                         blame_origin_incref(porigin);
1464                         origin->previous = porigin;
1465                 }
1466                 pass_blame_to_parent(sb, origin, porigin);
1467                 if (!origin->suspects)
1468                         goto finish;
1469         }
1470
1471         /*
1472          * Optionally find moves in parents' files.
1473          */
1474         if (opt & PICKAXE_BLAME_MOVE) {
1475                 filter_small(sb, &toosmall, &origin->suspects, sb->move_score);
1476                 if (origin->suspects) {
1477                         for (i = 0, sg = first_scapegoat(revs, commit, sb->reverse);
1478                              i < num_sg && sg;
1479                              sg = sg->next, i++) {
1480                                 struct blame_origin *porigin = sg_origin[i];
1481                                 if (!porigin)
1482                                         continue;
1483                                 find_move_in_parent(sb, &blametail, &toosmall, origin, porigin);
1484                                 if (!origin->suspects)
1485                                         break;
1486                         }
1487                 }
1488         }
1489
1490         /*
1491          * Optionally find copies from parents' files.
1492          */
1493         if (opt & PICKAXE_BLAME_COPY) {
1494                 if (sb->copy_score > sb->move_score)
1495                         filter_small(sb, &toosmall, &origin->suspects, sb->copy_score);
1496                 else if (sb->copy_score < sb->move_score) {
1497                         origin->suspects = blame_merge(origin->suspects, toosmall);
1498                         toosmall = NULL;
1499                         filter_small(sb, &toosmall, &origin->suspects, sb->copy_score);
1500                 }
1501                 if (!origin->suspects)
1502                         goto finish;
1503
1504                 for (i = 0, sg = first_scapegoat(revs, commit, sb->reverse);
1505                      i < num_sg && sg;
1506                      sg = sg->next, i++) {
1507                         struct blame_origin *porigin = sg_origin[i];
1508                         find_copy_in_parent(sb, &blametail, &toosmall,
1509                                             origin, sg->item, porigin, opt);
1510                         if (!origin->suspects)
1511                                 goto finish;
1512                 }
1513         }
1514
1515 finish:
1516         *blametail = NULL;
1517         distribute_blame(sb, blames);
1518         /*
1519          * prepend toosmall to origin->suspects
1520          *
1521          * There is no point in sorting: this ends up on a big
1522          * unsorted list in the caller anyway.
1523          */
1524         if (toosmall) {
1525                 struct blame_entry **tail = &toosmall;
1526                 while (*tail)
1527                         tail = &(*tail)->next;
1528                 *tail = origin->suspects;
1529                 origin->suspects = toosmall;
1530         }
1531         for (i = 0; i < num_sg; i++) {
1532                 if (sg_origin[i]) {
1533                         drop_origin_blob(sg_origin[i]);
1534                         blame_origin_decref(sg_origin[i]);
1535                 }
1536         }
1537         drop_origin_blob(origin);
1538         if (sg_buf != sg_origin)
1539                 free(sg_origin);
1540 }
1541
1542 /*
1543  * The main loop -- while we have blobs with lines whose true origin
1544  * is still unknown, pick one blob, and allow its lines to pass blames
1545  * to its parents. */
1546 void assign_blame(struct blame_scoreboard *sb, int opt)
1547 {
1548         struct rev_info *revs = sb->revs;
1549         struct commit *commit = prio_queue_get(&sb->commits);
1550
1551         while (commit) {
1552                 struct blame_entry *ent;
1553                 struct blame_origin *suspect = commit->util;
1554
1555                 /* find one suspect to break down */
1556                 while (suspect && !suspect->suspects)
1557                         suspect = suspect->next;
1558
1559                 if (!suspect) {
1560                         commit = prio_queue_get(&sb->commits);
1561                         continue;
1562                 }
1563
1564                 assert(commit == suspect->commit);
1565
1566                 /*
1567                  * We will use this suspect later in the loop,
1568                  * so hold onto it in the meantime.
1569                  */
1570                 blame_origin_incref(suspect);
1571                 parse_commit(commit);
1572                 if (sb->reverse ||
1573                     (!(commit->object.flags & UNINTERESTING) &&
1574                      !(revs->max_age != -1 && commit->date < revs->max_age)))
1575                         pass_blame(sb, suspect, opt);
1576                 else {
1577                         commit->object.flags |= UNINTERESTING;
1578                         if (commit->object.parsed)
1579                                 mark_parents_uninteresting(commit);
1580                 }
1581                 /* treat root commit as boundary */
1582                 if (!commit->parents && !sb->show_root)
1583                         commit->object.flags |= UNINTERESTING;
1584
1585                 /* Take responsibility for the remaining entries */
1586                 ent = suspect->suspects;
1587                 if (ent) {
1588                         suspect->guilty = 1;
1589                         for (;;) {
1590                                 struct blame_entry *next = ent->next;
1591                                 if (sb->found_guilty_entry)
1592                                         sb->found_guilty_entry(ent, sb->found_guilty_entry_data);
1593                                 if (next) {
1594                                         ent = next;
1595                                         continue;
1596                                 }
1597                                 ent->next = sb->ent;
1598                                 sb->ent = suspect->suspects;
1599                                 suspect->suspects = NULL;
1600                                 break;
1601                         }
1602                 }
1603                 blame_origin_decref(suspect);
1604
1605                 if (sb->debug) /* sanity */
1606                         sanity_check_refcnt(sb);
1607         }
1608 }
1609
1610 static const char *get_next_line(const char *start, const char *end)
1611 {
1612         const char *nl = memchr(start, '\n', end - start);
1613         return nl ? nl + 1 : end;
1614 }
1615
1616 /*
1617  * To allow quick access to the contents of nth line in the
1618  * final image, prepare an index in the scoreboard.
1619  */
1620 static int prepare_lines(struct blame_scoreboard *sb)
1621 {
1622         const char *buf = sb->final_buf;
1623         unsigned long len = sb->final_buf_size;
1624         const char *end = buf + len;
1625         const char *p;
1626         int *lineno;
1627         int num = 0;
1628
1629         for (p = buf; p < end; p = get_next_line(p, end))
1630                 num++;
1631
1632         ALLOC_ARRAY(sb->lineno, num + 1);
1633         lineno = sb->lineno;
1634
1635         for (p = buf; p < end; p = get_next_line(p, end))
1636                 *lineno++ = p - buf;
1637
1638         *lineno = len;
1639
1640         sb->num_lines = num;
1641         return sb->num_lines;
1642 }
1643
1644 static struct commit *find_single_final(struct rev_info *revs,
1645                                         const char **name_p)
1646 {
1647         int i;
1648         struct commit *found = NULL;
1649         const char *name = NULL;
1650
1651         for (i = 0; i < revs->pending.nr; i++) {
1652                 struct object *obj = revs->pending.objects[i].item;
1653                 if (obj->flags & UNINTERESTING)
1654                         continue;
1655                 obj = deref_tag(obj, NULL, 0);
1656                 if (obj->type != OBJ_COMMIT)
1657                         die("Non commit %s?", revs->pending.objects[i].name);
1658                 if (found)
1659                         die("More than one commit to dig from %s and %s?",
1660                             revs->pending.objects[i].name, name);
1661                 found = (struct commit *)obj;
1662                 name = revs->pending.objects[i].name;
1663         }
1664         if (name_p)
1665                 *name_p = xstrdup_or_null(name);
1666         return found;
1667 }
1668
1669 static struct commit *dwim_reverse_initial(struct rev_info *revs,
1670                                            const char **name_p)
1671 {
1672         /*
1673          * DWIM "git blame --reverse ONE -- PATH" as
1674          * "git blame --reverse ONE..HEAD -- PATH" but only do so
1675          * when it makes sense.
1676          */
1677         struct object *obj;
1678         struct commit *head_commit;
1679         struct object_id head_oid;
1680
1681         if (revs->pending.nr != 1)
1682                 return NULL;
1683
1684         /* Is that sole rev a committish? */
1685         obj = revs->pending.objects[0].item;
1686         obj = deref_tag(obj, NULL, 0);
1687         if (obj->type != OBJ_COMMIT)
1688                 return NULL;
1689
1690         /* Do we have HEAD? */
1691         if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
1692                 return NULL;
1693         head_commit = lookup_commit_reference_gently(&head_oid, 1);
1694         if (!head_commit)
1695                 return NULL;
1696
1697         /* Turn "ONE" into "ONE..HEAD" then */
1698         obj->flags |= UNINTERESTING;
1699         add_pending_object(revs, &head_commit->object, "HEAD");
1700
1701         if (name_p)
1702                 *name_p = revs->pending.objects[0].name;
1703         return (struct commit *)obj;
1704 }
1705
1706 static struct commit *find_single_initial(struct rev_info *revs,
1707                                           const char **name_p)
1708 {
1709         int i;
1710         struct commit *found = NULL;
1711         const char *name = NULL;
1712
1713         /*
1714          * There must be one and only one negative commit, and it must be
1715          * the boundary.
1716          */
1717         for (i = 0; i < revs->pending.nr; i++) {
1718                 struct object *obj = revs->pending.objects[i].item;
1719                 if (!(obj->flags & UNINTERESTING))
1720                         continue;
1721                 obj = deref_tag(obj, NULL, 0);
1722                 if (obj->type != OBJ_COMMIT)
1723                         die("Non commit %s?", revs->pending.objects[i].name);
1724                 if (found)
1725                         die("More than one commit to dig up from, %s and %s?",
1726                             revs->pending.objects[i].name, name);
1727                 found = (struct commit *) obj;
1728                 name = revs->pending.objects[i].name;
1729         }
1730
1731         if (!name)
1732                 found = dwim_reverse_initial(revs, &name);
1733         if (!name)
1734                 die("No commit to dig up from?");
1735
1736         if (name_p)
1737                 *name_p = xstrdup(name);
1738         return found;
1739 }
1740
1741 void init_scoreboard(struct blame_scoreboard *sb)
1742 {
1743         memset(sb, 0, sizeof(struct blame_scoreboard));
1744         sb->move_score = BLAME_DEFAULT_MOVE_SCORE;
1745         sb->copy_score = BLAME_DEFAULT_COPY_SCORE;
1746 }
1747
1748 void setup_scoreboard(struct blame_scoreboard *sb, const char *path, struct blame_origin **orig)
1749 {
1750         const char *final_commit_name = NULL;
1751         struct blame_origin *o;
1752         struct commit *final_commit = NULL;
1753         enum object_type type;
1754
1755         if (sb->reverse && sb->contents_from)
1756                 die(_("--contents and --reverse do not blend well."));
1757
1758         if (!sb->reverse) {
1759                 sb->final = find_single_final(sb->revs, &final_commit_name);
1760                 sb->commits.compare = compare_commits_by_commit_date;
1761         } else {
1762                 sb->final = find_single_initial(sb->revs, &final_commit_name);
1763                 sb->commits.compare = compare_commits_by_reverse_commit_date;
1764         }
1765
1766         if (sb->final && sb->contents_from)
1767                 die(_("cannot use --contents with final commit object name"));
1768
1769         if (sb->reverse && sb->revs->first_parent_only)
1770                 sb->revs->children.name = NULL;
1771
1772         if (!sb->final) {
1773                 /*
1774                  * "--not A B -- path" without anything positive;
1775                  * do not default to HEAD, but use the working tree
1776                  * or "--contents".
1777                  */
1778                 setup_work_tree();
1779                 sb->final = fake_working_tree_commit(&sb->revs->diffopt,
1780                                                      path, sb->contents_from);
1781                 add_pending_object(sb->revs, &(sb->final->object), ":");
1782         }
1783
1784         if (sb->reverse && sb->revs->first_parent_only) {
1785                 final_commit = find_single_final(sb->revs, NULL);
1786                 if (!final_commit)
1787                         die(_("--reverse and --first-parent together require specified latest commit"));
1788         }
1789
1790         /*
1791          * If we have bottom, this will mark the ancestors of the
1792          * bottom commits we would reach while traversing as
1793          * uninteresting.
1794          */
1795         if (prepare_revision_walk(sb->revs))
1796                 die(_("revision walk setup failed"));
1797
1798         if (sb->reverse && sb->revs->first_parent_only) {
1799                 struct commit *c = final_commit;
1800
1801                 sb->revs->children.name = "children";
1802                 while (c->parents &&
1803                        oidcmp(&c->object.oid, &sb->final->object.oid)) {
1804                         struct commit_list *l = xcalloc(1, sizeof(*l));
1805
1806                         l->item = c;
1807                         if (add_decoration(&sb->revs->children,
1808                                            &c->parents->item->object, l))
1809                                 BUG("not unique item in first-parent chain");
1810                         c = c->parents->item;
1811                 }
1812
1813                 if (oidcmp(&c->object.oid, &sb->final->object.oid))
1814                         die(_("--reverse --first-parent together require range along first-parent chain"));
1815         }
1816
1817         if (is_null_oid(&sb->final->object.oid)) {
1818                 o = sb->final->util;
1819                 sb->final_buf = xmemdupz(o->file.ptr, o->file.size);
1820                 sb->final_buf_size = o->file.size;
1821         }
1822         else {
1823                 o = get_origin(sb->final, path);
1824                 if (fill_blob_sha1_and_mode(o))
1825                         die(_("no such path %s in %s"), path, final_commit_name);
1826
1827                 if (sb->revs->diffopt.flags.allow_textconv &&
1828                     textconv_object(path, o->mode, &o->blob_oid, 1, (char **) &sb->final_buf,
1829                                     &sb->final_buf_size))
1830                         ;
1831                 else
1832                         sb->final_buf = read_object_file(&o->blob_oid, &type,
1833                                                          &sb->final_buf_size);
1834
1835                 if (!sb->final_buf)
1836                         die(_("cannot read blob %s for path %s"),
1837                             oid_to_hex(&o->blob_oid),
1838                             path);
1839         }
1840         sb->num_read_blob++;
1841         prepare_lines(sb);
1842
1843         if (orig)
1844                 *orig = o;
1845
1846         free((char *)final_commit_name);
1847 }
1848
1849
1850
1851 struct blame_entry *blame_entry_prepend(struct blame_entry *head,
1852                                         long start, long end,
1853                                         struct blame_origin *o)
1854 {
1855         struct blame_entry *new_head = xcalloc(1, sizeof(struct blame_entry));
1856         new_head->lno = start;
1857         new_head->num_lines = end - start;
1858         new_head->suspect = o;
1859         new_head->s_lno = start;
1860         new_head->next = head;
1861         blame_origin_incref(o);
1862         return new_head;
1863 }