Merge branch 'ab/i18n-envsubst-doc-fix'
[git] / bisect.c
1 #include "cache.h"
2 #include "commit.h"
3 #include "diff.h"
4 #include "revision.h"
5 #include "refs.h"
6 #include "list-objects.h"
7 #include "quote.h"
8 #include "sha1-lookup.h"
9 #include "run-command.h"
10 #include "log-tree.h"
11 #include "bisect.h"
12 #include "sha1-array.h"
13
14 static struct sha1_array good_revs;
15 static struct sha1_array skipped_revs;
16
17 static const unsigned char *current_bad_sha1;
18
19 struct argv_array {
20         const char **argv;
21         int argv_nr;
22         int argv_alloc;
23 };
24
25 static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
26 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
27
28 /* bits #0-15 in revision.h */
29
30 #define COUNTED         (1u<<16)
31
32 /*
33  * This is a truly stupid algorithm, but it's only
34  * used for bisection, and we just don't care enough.
35  *
36  * We care just barely enough to avoid recursing for
37  * non-merge entries.
38  */
39 static int count_distance(struct commit_list *entry)
40 {
41         int nr = 0;
42
43         while (entry) {
44                 struct commit *commit = entry->item;
45                 struct commit_list *p;
46
47                 if (commit->object.flags & (UNINTERESTING | COUNTED))
48                         break;
49                 if (!(commit->object.flags & TREESAME))
50                         nr++;
51                 commit->object.flags |= COUNTED;
52                 p = commit->parents;
53                 entry = p;
54                 if (p) {
55                         p = p->next;
56                         while (p) {
57                                 nr += count_distance(p);
58                                 p = p->next;
59                         }
60                 }
61         }
62
63         return nr;
64 }
65
66 static void clear_distance(struct commit_list *list)
67 {
68         while (list) {
69                 struct commit *commit = list->item;
70                 commit->object.flags &= ~COUNTED;
71                 list = list->next;
72         }
73 }
74
75 #define DEBUG_BISECT 0
76
77 static inline int weight(struct commit_list *elem)
78 {
79         return *((int*)(elem->item->util));
80 }
81
82 static inline void weight_set(struct commit_list *elem, int weight)
83 {
84         *((int*)(elem->item->util)) = weight;
85 }
86
87 static int count_interesting_parents(struct commit *commit)
88 {
89         struct commit_list *p;
90         int count;
91
92         for (count = 0, p = commit->parents; p; p = p->next) {
93                 if (p->item->object.flags & UNINTERESTING)
94                         continue;
95                 count++;
96         }
97         return count;
98 }
99
100 static inline int halfway(struct commit_list *p, int nr)
101 {
102         /*
103          * Don't short-cut something we are not going to return!
104          */
105         if (p->item->object.flags & TREESAME)
106                 return 0;
107         if (DEBUG_BISECT)
108                 return 0;
109         /*
110          * 2 and 3 are halfway of 5.
111          * 3 is halfway of 6 but 2 and 4 are not.
112          */
113         switch (2 * weight(p) - nr) {
114         case -1: case 0: case 1:
115                 return 1;
116         default:
117                 return 0;
118         }
119 }
120
121 #if !DEBUG_BISECT
122 #define show_list(a,b,c,d) do { ; } while (0)
123 #else
124 static void show_list(const char *debug, int counted, int nr,
125                       struct commit_list *list)
126 {
127         struct commit_list *p;
128
129         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
130
131         for (p = list; p; p = p->next) {
132                 struct commit_list *pp;
133                 struct commit *commit = p->item;
134                 unsigned flags = commit->object.flags;
135                 enum object_type type;
136                 unsigned long size;
137                 char *buf = read_sha1_file(commit->object.sha1, &type, &size);
138                 const char *subject_start;
139                 int subject_len;
140
141                 fprintf(stderr, "%c%c%c ",
142                         (flags & TREESAME) ? ' ' : 'T',
143                         (flags & UNINTERESTING) ? 'U' : ' ',
144                         (flags & COUNTED) ? 'C' : ' ');
145                 if (commit->util)
146                         fprintf(stderr, "%3d", weight(p));
147                 else
148                         fprintf(stderr, "---");
149                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
150                 for (pp = commit->parents; pp; pp = pp->next)
151                         fprintf(stderr, " %.*s", 8,
152                                 sha1_to_hex(pp->item->object.sha1));
153
154                 subject_len = find_commit_subject(buf, &subject_start);
155                 if (subject_len)
156                         fprintf(stderr, " %.*s", subject_len, subject_start);
157                 fprintf(stderr, "\n");
158         }
159 }
160 #endif /* DEBUG_BISECT */
161
162 static struct commit_list *best_bisection(struct commit_list *list, int nr)
163 {
164         struct commit_list *p, *best;
165         int best_distance = -1;
166
167         best = list;
168         for (p = list; p; p = p->next) {
169                 int distance;
170                 unsigned flags = p->item->object.flags;
171
172                 if (flags & TREESAME)
173                         continue;
174                 distance = weight(p);
175                 if (nr - distance < distance)
176                         distance = nr - distance;
177                 if (distance > best_distance) {
178                         best = p;
179                         best_distance = distance;
180                 }
181         }
182
183         return best;
184 }
185
186 struct commit_dist {
187         struct commit *commit;
188         int distance;
189 };
190
191 static int compare_commit_dist(const void *a_, const void *b_)
192 {
193         struct commit_dist *a, *b;
194
195         a = (struct commit_dist *)a_;
196         b = (struct commit_dist *)b_;
197         if (a->distance != b->distance)
198                 return b->distance - a->distance; /* desc sort */
199         return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
200 }
201
202 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
203 {
204         struct commit_list *p;
205         struct commit_dist *array = xcalloc(nr, sizeof(*array));
206         int cnt, i;
207
208         for (p = list, cnt = 0; p; p = p->next) {
209                 int distance;
210                 unsigned flags = p->item->object.flags;
211
212                 if (flags & TREESAME)
213                         continue;
214                 distance = weight(p);
215                 if (nr - distance < distance)
216                         distance = nr - distance;
217                 array[cnt].commit = p->item;
218                 array[cnt].distance = distance;
219                 cnt++;
220         }
221         qsort(array, cnt, sizeof(*array), compare_commit_dist);
222         for (p = list, i = 0; i < cnt; i++) {
223                 struct name_decoration *r = xmalloc(sizeof(*r) + 100);
224                 struct object *obj = &(array[i].commit->object);
225
226                 sprintf(r->name, "dist=%d", array[i].distance);
227                 r->next = add_decoration(&name_decoration, obj, r);
228                 p->item = array[i].commit;
229                 p = p->next;
230         }
231         if (p)
232                 p->next = NULL;
233         free(array);
234         return list;
235 }
236
237 /*
238  * zero or positive weight is the number of interesting commits it can
239  * reach, including itself.  Especially, weight = 0 means it does not
240  * reach any tree-changing commits (e.g. just above uninteresting one
241  * but traversal is with pathspec).
242  *
243  * weight = -1 means it has one parent and its distance is yet to
244  * be computed.
245  *
246  * weight = -2 means it has more than one parent and its distance is
247  * unknown.  After running count_distance() first, they will get zero
248  * or positive distance.
249  */
250 static struct commit_list *do_find_bisection(struct commit_list *list,
251                                              int nr, int *weights,
252                                              int find_all)
253 {
254         int n, counted;
255         struct commit_list *p;
256
257         counted = 0;
258
259         for (n = 0, p = list; p; p = p->next) {
260                 struct commit *commit = p->item;
261                 unsigned flags = commit->object.flags;
262
263                 p->item->util = &weights[n++];
264                 switch (count_interesting_parents(commit)) {
265                 case 0:
266                         if (!(flags & TREESAME)) {
267                                 weight_set(p, 1);
268                                 counted++;
269                                 show_list("bisection 2 count one",
270                                           counted, nr, list);
271                         }
272                         /*
273                          * otherwise, it is known not to reach any
274                          * tree-changing commit and gets weight 0.
275                          */
276                         break;
277                 case 1:
278                         weight_set(p, -1);
279                         break;
280                 default:
281                         weight_set(p, -2);
282                         break;
283                 }
284         }
285
286         show_list("bisection 2 initialize", counted, nr, list);
287
288         /*
289          * If you have only one parent in the resulting set
290          * then you can reach one commit more than that parent
291          * can reach.  So we do not have to run the expensive
292          * count_distance() for single strand of pearls.
293          *
294          * However, if you have more than one parents, you cannot
295          * just add their distance and one for yourself, since
296          * they usually reach the same ancestor and you would
297          * end up counting them twice that way.
298          *
299          * So we will first count distance of merges the usual
300          * way, and then fill the blanks using cheaper algorithm.
301          */
302         for (p = list; p; p = p->next) {
303                 if (p->item->object.flags & UNINTERESTING)
304                         continue;
305                 if (weight(p) != -2)
306                         continue;
307                 weight_set(p, count_distance(p));
308                 clear_distance(list);
309
310                 /* Does it happen to be at exactly half-way? */
311                 if (!find_all && halfway(p, nr))
312                         return p;
313                 counted++;
314         }
315
316         show_list("bisection 2 count_distance", counted, nr, list);
317
318         while (counted < nr) {
319                 for (p = list; p; p = p->next) {
320                         struct commit_list *q;
321                         unsigned flags = p->item->object.flags;
322
323                         if (0 <= weight(p))
324                                 continue;
325                         for (q = p->item->parents; q; q = q->next) {
326                                 if (q->item->object.flags & UNINTERESTING)
327                                         continue;
328                                 if (0 <= weight(q))
329                                         break;
330                         }
331                         if (!q)
332                                 continue;
333
334                         /*
335                          * weight for p is unknown but q is known.
336                          * add one for p itself if p is to be counted,
337                          * otherwise inherit it from q directly.
338                          */
339                         if (!(flags & TREESAME)) {
340                                 weight_set(p, weight(q)+1);
341                                 counted++;
342                                 show_list("bisection 2 count one",
343                                           counted, nr, list);
344                         }
345                         else
346                                 weight_set(p, weight(q));
347
348                         /* Does it happen to be at exactly half-way? */
349                         if (!find_all && halfway(p, nr))
350                                 return p;
351                 }
352         }
353
354         show_list("bisection 2 counted all", counted, nr, list);
355
356         if (!find_all)
357                 return best_bisection(list, nr);
358         else
359                 return best_bisection_sorted(list, nr);
360 }
361
362 struct commit_list *find_bisection(struct commit_list *list,
363                                           int *reaches, int *all,
364                                           int find_all)
365 {
366         int nr, on_list;
367         struct commit_list *p, *best, *next, *last;
368         int *weights;
369
370         show_list("bisection 2 entry", 0, 0, list);
371
372         /*
373          * Count the number of total and tree-changing items on the
374          * list, while reversing the list.
375          */
376         for (nr = on_list = 0, last = NULL, p = list;
377              p;
378              p = next) {
379                 unsigned flags = p->item->object.flags;
380
381                 next = p->next;
382                 if (flags & UNINTERESTING)
383                         continue;
384                 p->next = last;
385                 last = p;
386                 if (!(flags & TREESAME))
387                         nr++;
388                 on_list++;
389         }
390         list = last;
391         show_list("bisection 2 sorted", 0, nr, list);
392
393         *all = nr;
394         weights = xcalloc(on_list, sizeof(*weights));
395
396         /* Do the real work of finding bisection commit. */
397         best = do_find_bisection(list, nr, weights, find_all);
398         if (best) {
399                 if (!find_all)
400                         best->next = NULL;
401                 *reaches = weight(best);
402         }
403         free(weights);
404         return best;
405 }
406
407 static void argv_array_push(struct argv_array *array, const char *string)
408 {
409         ALLOC_GROW(array->argv, array->argv_nr + 1, array->argv_alloc);
410         array->argv[array->argv_nr++] = string;
411 }
412
413 static void argv_array_push_sha1(struct argv_array *array,
414                                  const unsigned char *sha1,
415                                  const char *format)
416 {
417         struct strbuf buf = STRBUF_INIT;
418         strbuf_addf(&buf, format, sha1_to_hex(sha1));
419         argv_array_push(array, strbuf_detach(&buf, NULL));
420 }
421
422 static int register_ref(const char *refname, const unsigned char *sha1,
423                         int flags, void *cb_data)
424 {
425         if (!strcmp(refname, "bad")) {
426                 current_bad_sha1 = sha1;
427         } else if (!prefixcmp(refname, "good-")) {
428                 sha1_array_append(&good_revs, sha1);
429         } else if (!prefixcmp(refname, "skip-")) {
430                 sha1_array_append(&skipped_revs, sha1);
431         }
432
433         return 0;
434 }
435
436 static int read_bisect_refs(void)
437 {
438         return for_each_ref_in("refs/bisect/", register_ref, NULL);
439 }
440
441 static void read_bisect_paths(struct argv_array *array)
442 {
443         struct strbuf str = STRBUF_INIT;
444         const char *filename = git_path("BISECT_NAMES");
445         FILE *fp = fopen(filename, "r");
446
447         if (!fp)
448                 die_errno("Could not open file '%s'", filename);
449
450         while (strbuf_getline(&str, fp, '\n') != EOF) {
451                 char *quoted;
452                 int res;
453
454                 strbuf_trim(&str);
455                 quoted = strbuf_detach(&str, NULL);
456                 res = sq_dequote_to_argv(quoted, &array->argv,
457                                          &array->argv_nr, &array->argv_alloc);
458                 if (res)
459                         die("Badly quoted content in file '%s': %s",
460                             filename, quoted);
461         }
462
463         strbuf_release(&str);
464         fclose(fp);
465 }
466
467 static char *join_sha1_array_hex(struct sha1_array *array, char delim)
468 {
469         struct strbuf joined_hexs = STRBUF_INIT;
470         int i;
471
472         for (i = 0; i < array->nr; i++) {
473                 strbuf_addstr(&joined_hexs, sha1_to_hex(array->sha1[i]));
474                 if (i + 1 < array->nr)
475                         strbuf_addch(&joined_hexs, delim);
476         }
477
478         return strbuf_detach(&joined_hexs, NULL);
479 }
480
481 /*
482  * In this function, passing a not NULL skipped_first is very special.
483  * It means that we want to know if the first commit in the list is
484  * skipped because we will want to test a commit away from it if it is
485  * indeed skipped.
486  * So if the first commit is skipped, we cannot take the shortcut to
487  * just "return list" when we find the first non skipped commit, we
488  * have to return a fully filtered list.
489  *
490  * We use (*skipped_first == -1) to mean "it has been found that the
491  * first commit is not skipped". In this case *skipped_first is set back
492  * to 0 just before the function returns.
493  */
494 struct commit_list *filter_skipped(struct commit_list *list,
495                                    struct commit_list **tried,
496                                    int show_all,
497                                    int *count,
498                                    int *skipped_first)
499 {
500         struct commit_list *filtered = NULL, **f = &filtered;
501
502         *tried = NULL;
503
504         if (skipped_first)
505                 *skipped_first = 0;
506         if (count)
507                 *count = 0;
508
509         if (!skipped_revs.nr)
510                 return list;
511
512         while (list) {
513                 struct commit_list *next = list->next;
514                 list->next = NULL;
515                 if (0 <= sha1_array_lookup(&skipped_revs,
516                                            list->item->object.sha1)) {
517                         if (skipped_first && !*skipped_first)
518                                 *skipped_first = 1;
519                         /* Move current to tried list */
520                         *tried = list;
521                         tried = &list->next;
522                 } else {
523                         if (!show_all) {
524                                 if (!skipped_first || !*skipped_first)
525                                         return list;
526                         } else if (skipped_first && !*skipped_first) {
527                                 /* This means we know it's not skipped */
528                                 *skipped_first = -1;
529                         }
530                         /* Move current to filtered list */
531                         *f = list;
532                         f = &list->next;
533                         if (count)
534                                 (*count)++;
535                 }
536                 list = next;
537         }
538
539         if (skipped_first && *skipped_first == -1)
540                 *skipped_first = 0;
541
542         return filtered;
543 }
544
545 #define PRN_MODULO 32768
546
547 /*
548  * This is a pseudo random number generator based on "man 3 rand".
549  * It is not used properly because the seed is the argument and it
550  * is increased by one between each call, but that should not matter
551  * for this application.
552  */
553 static int get_prn(int count) {
554         count = count * 1103515245 + 12345;
555         return ((unsigned)(count/65536) % PRN_MODULO);
556 }
557
558 /*
559  * Custom integer square root from
560  * http://en.wikipedia.org/wiki/Integer_square_root
561  */
562 static int sqrti(int val)
563 {
564         float d, x = val;
565
566         if (val == 0)
567                 return 0;
568
569         do {
570                 float y = (x + (float)val / x) / 2;
571                 d = (y > x) ? y - x : x - y;
572                 x = y;
573         } while (d >= 0.5);
574
575         return (int)x;
576 }
577
578 static struct commit_list *skip_away(struct commit_list *list, int count)
579 {
580         struct commit_list *cur, *previous;
581         int prn, index, i;
582
583         prn = get_prn(count);
584         index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);
585
586         cur = list;
587         previous = NULL;
588
589         for (i = 0; cur; cur = cur->next, i++) {
590                 if (i == index) {
591                         if (hashcmp(cur->item->object.sha1, current_bad_sha1))
592                                 return cur;
593                         if (previous)
594                                 return previous;
595                         return list;
596                 }
597                 previous = cur;
598         }
599
600         return list;
601 }
602
603 static struct commit_list *managed_skipped(struct commit_list *list,
604                                            struct commit_list **tried)
605 {
606         int count, skipped_first;
607
608         *tried = NULL;
609
610         if (!skipped_revs.nr)
611                 return list;
612
613         list = filter_skipped(list, tried, 0, &count, &skipped_first);
614
615         if (!skipped_first)
616                 return list;
617
618         return skip_away(list, count);
619 }
620
621 static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
622                              const char *bad_format, const char *good_format,
623                              int read_paths)
624 {
625         struct argv_array rev_argv = { NULL, 0, 0 };
626         int i;
627
628         init_revisions(revs, prefix);
629         revs->abbrev = 0;
630         revs->commit_format = CMIT_FMT_UNSPECIFIED;
631
632         /* rev_argv.argv[0] will be ignored by setup_revisions */
633         argv_array_push(&rev_argv, xstrdup("bisect_rev_setup"));
634         argv_array_push_sha1(&rev_argv, current_bad_sha1, bad_format);
635         for (i = 0; i < good_revs.nr; i++)
636                 argv_array_push_sha1(&rev_argv, good_revs.sha1[i],
637                                      good_format);
638         argv_array_push(&rev_argv, xstrdup("--"));
639         if (read_paths)
640                 read_bisect_paths(&rev_argv);
641         argv_array_push(&rev_argv, NULL);
642
643         setup_revisions(rev_argv.argv_nr, rev_argv.argv, revs, NULL);
644 }
645
646 static void bisect_common(struct rev_info *revs)
647 {
648         if (prepare_revision_walk(revs))
649                 die("revision walk setup failed");
650         if (revs->tree_objects)
651                 mark_edges_uninteresting(revs->commits, revs, NULL);
652 }
653
654 static void exit_if_skipped_commits(struct commit_list *tried,
655                                     const unsigned char *bad)
656 {
657         if (!tried)
658                 return;
659
660         printf("There are only 'skip'ped commits left to test.\n"
661                "The first bad commit could be any of:\n");
662         print_commit_list(tried, "%s\n", "%s\n");
663         if (bad)
664                 printf("%s\n", sha1_to_hex(bad));
665         printf("We cannot bisect more!\n");
666         exit(2);
667 }
668
669 static int is_expected_rev(const unsigned char *sha1)
670 {
671         const char *filename = git_path("BISECT_EXPECTED_REV");
672         struct stat st;
673         struct strbuf str = STRBUF_INIT;
674         FILE *fp;
675         int res = 0;
676
677         if (stat(filename, &st) || !S_ISREG(st.st_mode))
678                 return 0;
679
680         fp = fopen(filename, "r");
681         if (!fp)
682                 return 0;
683
684         if (strbuf_getline(&str, fp, '\n') != EOF)
685                 res = !strcmp(str.buf, sha1_to_hex(sha1));
686
687         strbuf_release(&str);
688         fclose(fp);
689
690         return res;
691 }
692
693 static void mark_expected_rev(char *bisect_rev_hex)
694 {
695         int len = strlen(bisect_rev_hex);
696         const char *filename = git_path("BISECT_EXPECTED_REV");
697         int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
698
699         if (fd < 0)
700                 die_errno("could not create file '%s'", filename);
701
702         bisect_rev_hex[len] = '\n';
703         write_or_die(fd, bisect_rev_hex, len + 1);
704         bisect_rev_hex[len] = '\0';
705
706         if (close(fd) < 0)
707                 die("closing file %s: %s", filename, strerror(errno));
708 }
709
710 static int bisect_checkout(char *bisect_rev_hex)
711 {
712         int res;
713
714         mark_expected_rev(bisect_rev_hex);
715
716         argv_checkout[2] = bisect_rev_hex;
717         res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
718         if (res)
719                 exit(res);
720
721         argv_show_branch[1] = bisect_rev_hex;
722         return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
723 }
724
725 static struct commit *get_commit_reference(const unsigned char *sha1)
726 {
727         struct commit *r = lookup_commit_reference(sha1);
728         if (!r)
729                 die("Not a valid commit name %s", sha1_to_hex(sha1));
730         return r;
731 }
732
733 static struct commit **get_bad_and_good_commits(int *rev_nr)
734 {
735         int len = 1 + good_revs.nr;
736         struct commit **rev = xmalloc(len * sizeof(*rev));
737         int i, n = 0;
738
739         rev[n++] = get_commit_reference(current_bad_sha1);
740         for (i = 0; i < good_revs.nr; i++)
741                 rev[n++] = get_commit_reference(good_revs.sha1[i]);
742         *rev_nr = n;
743
744         return rev;
745 }
746
747 static void handle_bad_merge_base(void)
748 {
749         if (is_expected_rev(current_bad_sha1)) {
750                 char *bad_hex = sha1_to_hex(current_bad_sha1);
751                 char *good_hex = join_sha1_array_hex(&good_revs, ' ');
752
753                 fprintf(stderr, "The merge base %s is bad.\n"
754                         "This means the bug has been fixed "
755                         "between %s and [%s].\n",
756                         bad_hex, bad_hex, good_hex);
757
758                 exit(3);
759         }
760
761         fprintf(stderr, "Some good revs are not ancestor of the bad rev.\n"
762                 "git bisect cannot work properly in this case.\n"
763                 "Maybe you mistake good and bad revs?\n");
764         exit(1);
765 }
766
767 static void handle_skipped_merge_base(const unsigned char *mb)
768 {
769         char *mb_hex = sha1_to_hex(mb);
770         char *bad_hex = sha1_to_hex(current_bad_sha1);
771         char *good_hex = join_sha1_array_hex(&good_revs, ' ');
772
773         warning("the merge base between %s and [%s] "
774                 "must be skipped.\n"
775                 "So we cannot be sure the first bad commit is "
776                 "between %s and %s.\n"
777                 "We continue anyway.",
778                 bad_hex, good_hex, mb_hex, bad_hex);
779         free(good_hex);
780 }
781
782 /*
783  * "check_merge_bases" checks that merge bases are not "bad".
784  *
785  * - If one is "bad", it means the user assumed something wrong
786  * and we must exit with a non 0 error code.
787  * - If one is "good", that's good, we have nothing to do.
788  * - If one is "skipped", we can't know but we should warn.
789  * - If we don't know, we should check it out and ask the user to test.
790  */
791 static void check_merge_bases(void)
792 {
793         struct commit_list *result;
794         int rev_nr;
795         struct commit **rev = get_bad_and_good_commits(&rev_nr);
796
797         result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 0);
798
799         for (; result; result = result->next) {
800                 const unsigned char *mb = result->item->object.sha1;
801                 if (!hashcmp(mb, current_bad_sha1)) {
802                         handle_bad_merge_base();
803                 } else if (0 <= sha1_array_lookup(&good_revs, mb)) {
804                         continue;
805                 } else if (0 <= sha1_array_lookup(&skipped_revs, mb)) {
806                         handle_skipped_merge_base(mb);
807                 } else {
808                         printf("Bisecting: a merge base must be tested\n");
809                         exit(bisect_checkout(sha1_to_hex(mb)));
810                 }
811         }
812
813         free(rev);
814         free_commit_list(result);
815 }
816
817 static int check_ancestors(const char *prefix)
818 {
819         struct rev_info revs;
820         struct object_array pending_copy;
821         int i, res;
822
823         bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
824
825         /* Save pending objects, so they can be cleaned up later. */
826         memset(&pending_copy, 0, sizeof(pending_copy));
827         for (i = 0; i < revs.pending.nr; i++)
828                 add_object_array(revs.pending.objects[i].item,
829                                  revs.pending.objects[i].name,
830                                  &pending_copy);
831
832         bisect_common(&revs);
833         res = (revs.commits != NULL);
834
835         /* Clean up objects used, as they will be reused. */
836         for (i = 0; i < pending_copy.nr; i++) {
837                 struct object *o = pending_copy.objects[i].item;
838                 clear_commit_marks((struct commit *)o, ALL_REV_FLAGS);
839         }
840
841         return res;
842 }
843
844 /*
845  * "check_good_are_ancestors_of_bad" checks that all "good" revs are
846  * ancestor of the "bad" rev.
847  *
848  * If that's not the case, we need to check the merge bases.
849  * If a merge base must be tested by the user, its source code will be
850  * checked out to be tested by the user and we will exit.
851  */
852 static void check_good_are_ancestors_of_bad(const char *prefix)
853 {
854         const char *filename = git_path("BISECT_ANCESTORS_OK");
855         struct stat st;
856         int fd;
857
858         if (!current_bad_sha1)
859                 die("a bad revision is needed");
860
861         /* Check if file BISECT_ANCESTORS_OK exists. */
862         if (!stat(filename, &st) && S_ISREG(st.st_mode))
863                 return;
864
865         /* Bisecting with no good rev is ok. */
866         if (good_revs.nr == 0)
867                 return;
868
869         /* Check if all good revs are ancestor of the bad rev. */
870         if (check_ancestors(prefix))
871                 check_merge_bases();
872
873         /* Create file BISECT_ANCESTORS_OK. */
874         fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
875         if (fd < 0)
876                 warning("could not create file '%s': %s",
877                         filename, strerror(errno));
878         else
879                 close(fd);
880 }
881
882 /*
883  * This does "git diff-tree --pretty COMMIT" without one fork+exec.
884  */
885 static void show_diff_tree(const char *prefix, struct commit *commit)
886 {
887         struct rev_info opt;
888
889         /* diff-tree init */
890         init_revisions(&opt, prefix);
891         git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
892         opt.abbrev = 0;
893         opt.diff = 1;
894
895         /* This is what "--pretty" does */
896         opt.verbose_header = 1;
897         opt.use_terminator = 0;
898         opt.commit_format = CMIT_FMT_DEFAULT;
899
900         /* diff-tree init */
901         if (!opt.diffopt.output_format)
902                 opt.diffopt.output_format = DIFF_FORMAT_RAW;
903
904         log_tree_commit(&opt, commit);
905 }
906
907 /*
908  * We use the convention that exiting with an exit code 10 means that
909  * the bisection process finished successfully.
910  * In this case the calling shell script should exit 0.
911  */
912 int bisect_next_all(const char *prefix)
913 {
914         struct rev_info revs;
915         struct commit_list *tried;
916         int reaches = 0, all = 0, nr, steps;
917         const unsigned char *bisect_rev;
918         char bisect_rev_hex[41];
919
920         if (read_bisect_refs())
921                 die("reading bisect refs failed");
922
923         check_good_are_ancestors_of_bad(prefix);
924
925         bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
926         revs.limited = 1;
927
928         bisect_common(&revs);
929
930         revs.commits = find_bisection(revs.commits, &reaches, &all,
931                                        !!skipped_revs.nr);
932         revs.commits = managed_skipped(revs.commits, &tried);
933
934         if (!revs.commits) {
935                 /*
936                  * We should exit here only if the "bad"
937                  * commit is also a "skip" commit.
938                  */
939                 exit_if_skipped_commits(tried, NULL);
940
941                 printf("%s was both good and bad\n",
942                        sha1_to_hex(current_bad_sha1));
943                 exit(1);
944         }
945
946         if (!all) {
947                 fprintf(stderr, "No testable commit found.\n"
948                         "Maybe you started with bad path parameters?\n");
949                 exit(4);
950         }
951
952         bisect_rev = revs.commits->item->object.sha1;
953         memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), 41);
954
955         if (!hashcmp(bisect_rev, current_bad_sha1)) {
956                 exit_if_skipped_commits(tried, current_bad_sha1);
957                 printf("%s is the first bad commit\n", bisect_rev_hex);
958                 show_diff_tree(prefix, revs.commits->item);
959                 /* This means the bisection process succeeded. */
960                 exit(10);
961         }
962
963         nr = all - reaches - 1;
964         steps = estimate_bisect_steps(all);
965         printf("Bisecting: %d revision%s left to test after this "
966                "(roughly %d step%s)\n", nr, (nr == 1 ? "" : "s"),
967                steps, (steps == 1 ? "" : "s"));
968
969         return bisect_checkout(bisect_rev_hex);
970 }
971