Merge branch 'nd/conditional-config-in-early-config'
[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 #include "argv-array.h"
14
15 static struct oid_array good_revs;
16 static struct oid_array skipped_revs;
17
18 static struct object_id *current_bad_oid;
19
20 static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
21 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
22
23 static const char *term_bad;
24 static const char *term_good;
25
26 /* Remember to update object flag allocation in object.h */
27 #define COUNTED         (1u<<16)
28
29 /*
30  * This is a truly stupid algorithm, but it's only
31  * used for bisection, and we just don't care enough.
32  *
33  * We care just barely enough to avoid recursing for
34  * non-merge entries.
35  */
36 static int count_distance(struct commit_list *entry)
37 {
38         int nr = 0;
39
40         while (entry) {
41                 struct commit *commit = entry->item;
42                 struct commit_list *p;
43
44                 if (commit->object.flags & (UNINTERESTING | COUNTED))
45                         break;
46                 if (!(commit->object.flags & TREESAME))
47                         nr++;
48                 commit->object.flags |= COUNTED;
49                 p = commit->parents;
50                 entry = p;
51                 if (p) {
52                         p = p->next;
53                         while (p) {
54                                 nr += count_distance(p);
55                                 p = p->next;
56                         }
57                 }
58         }
59
60         return nr;
61 }
62
63 static void clear_distance(struct commit_list *list)
64 {
65         while (list) {
66                 struct commit *commit = list->item;
67                 commit->object.flags &= ~COUNTED;
68                 list = list->next;
69         }
70 }
71
72 #define DEBUG_BISECT 0
73
74 static inline int weight(struct commit_list *elem)
75 {
76         return *((int*)(elem->item->util));
77 }
78
79 static inline void weight_set(struct commit_list *elem, int weight)
80 {
81         *((int*)(elem->item->util)) = weight;
82 }
83
84 static int count_interesting_parents(struct commit *commit)
85 {
86         struct commit_list *p;
87         int count;
88
89         for (count = 0, p = commit->parents; p; p = p->next) {
90                 if (p->item->object.flags & UNINTERESTING)
91                         continue;
92                 count++;
93         }
94         return count;
95 }
96
97 static inline int halfway(struct commit_list *p, int nr)
98 {
99         /*
100          * Don't short-cut something we are not going to return!
101          */
102         if (p->item->object.flags & TREESAME)
103                 return 0;
104         if (DEBUG_BISECT)
105                 return 0;
106         /*
107          * 2 and 3 are halfway of 5.
108          * 3 is halfway of 6 but 2 and 4 are not.
109          */
110         switch (2 * weight(p) - nr) {
111         case -1: case 0: case 1:
112                 return 1;
113         default:
114                 return 0;
115         }
116 }
117
118 #if !DEBUG_BISECT
119 #define show_list(a,b,c,d) do { ; } while (0)
120 #else
121 static void show_list(const char *debug, int counted, int nr,
122                       struct commit_list *list)
123 {
124         struct commit_list *p;
125
126         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
127
128         for (p = list; p; p = p->next) {
129                 struct commit_list *pp;
130                 struct commit *commit = p->item;
131                 unsigned flags = commit->object.flags;
132                 enum object_type type;
133                 unsigned long size;
134                 char *buf = read_sha1_file(commit->object.sha1, &type, &size);
135                 const char *subject_start;
136                 int subject_len;
137
138                 fprintf(stderr, "%c%c%c ",
139                         (flags & TREESAME) ? ' ' : 'T',
140                         (flags & UNINTERESTING) ? 'U' : ' ',
141                         (flags & COUNTED) ? 'C' : ' ');
142                 if (commit->util)
143                         fprintf(stderr, "%3d", weight(p));
144                 else
145                         fprintf(stderr, "---");
146                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
147                 for (pp = commit->parents; pp; pp = pp->next)
148                         fprintf(stderr, " %.*s", 8,
149                                 sha1_to_hex(pp->item->object.sha1));
150
151                 subject_len = find_commit_subject(buf, &subject_start);
152                 if (subject_len)
153                         fprintf(stderr, " %.*s", subject_len, subject_start);
154                 fprintf(stderr, "\n");
155         }
156 }
157 #endif /* DEBUG_BISECT */
158
159 static struct commit_list *best_bisection(struct commit_list *list, int nr)
160 {
161         struct commit_list *p, *best;
162         int best_distance = -1;
163
164         best = list;
165         for (p = list; p; p = p->next) {
166                 int distance;
167                 unsigned flags = p->item->object.flags;
168
169                 if (flags & TREESAME)
170                         continue;
171                 distance = weight(p);
172                 if (nr - distance < distance)
173                         distance = nr - distance;
174                 if (distance > best_distance) {
175                         best = p;
176                         best_distance = distance;
177                 }
178         }
179
180         return best;
181 }
182
183 struct commit_dist {
184         struct commit *commit;
185         int distance;
186 };
187
188 static int compare_commit_dist(const void *a_, const void *b_)
189 {
190         struct commit_dist *a, *b;
191
192         a = (struct commit_dist *)a_;
193         b = (struct commit_dist *)b_;
194         if (a->distance != b->distance)
195                 return b->distance - a->distance; /* desc sort */
196         return oidcmp(&a->commit->object.oid, &b->commit->object.oid);
197 }
198
199 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
200 {
201         struct commit_list *p;
202         struct commit_dist *array = xcalloc(nr, sizeof(*array));
203         struct strbuf buf = STRBUF_INIT;
204         int cnt, i;
205
206         for (p = list, cnt = 0; p; p = p->next) {
207                 int distance;
208                 unsigned flags = p->item->object.flags;
209
210                 if (flags & TREESAME)
211                         continue;
212                 distance = weight(p);
213                 if (nr - distance < distance)
214                         distance = nr - distance;
215                 array[cnt].commit = p->item;
216                 array[cnt].distance = distance;
217                 cnt++;
218         }
219         QSORT(array, cnt, compare_commit_dist);
220         for (p = list, i = 0; i < cnt; i++) {
221                 struct object *obj = &(array[i].commit->object);
222
223                 strbuf_reset(&buf);
224                 strbuf_addf(&buf, "dist=%d", array[i].distance);
225                 add_name_decoration(DECORATION_NONE, buf.buf, obj);
226
227                 p->item = array[i].commit;
228                 p = p->next;
229         }
230         if (p)
231                 p->next = NULL;
232         strbuf_release(&buf);
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 int register_ref(const char *refname, const struct object_id *oid,
408                         int flags, void *cb_data)
409 {
410         struct strbuf good_prefix = STRBUF_INIT;
411         strbuf_addstr(&good_prefix, term_good);
412         strbuf_addstr(&good_prefix, "-");
413
414         if (!strcmp(refname, term_bad)) {
415                 current_bad_oid = xmalloc(sizeof(*current_bad_oid));
416                 oidcpy(current_bad_oid, oid);
417         } else if (starts_with(refname, good_prefix.buf)) {
418                 oid_array_append(&good_revs, oid);
419         } else if (starts_with(refname, "skip-")) {
420                 oid_array_append(&skipped_revs, oid);
421         }
422
423         strbuf_release(&good_prefix);
424
425         return 0;
426 }
427
428 static int read_bisect_refs(void)
429 {
430         return for_each_ref_in("refs/bisect/", register_ref, NULL);
431 }
432
433 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
434 static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
435
436 static void read_bisect_paths(struct argv_array *array)
437 {
438         struct strbuf str = STRBUF_INIT;
439         const char *filename = git_path_bisect_names();
440         FILE *fp = fopen(filename, "r");
441
442         if (!fp)
443                 die_errno(_("Could not open file '%s'"), filename);
444
445         while (strbuf_getline_lf(&str, fp) != EOF) {
446                 strbuf_trim(&str);
447                 if (sq_dequote_to_argv_array(str.buf, array))
448                         die(_("Badly quoted content in file '%s': %s"),
449                             filename, str.buf);
450         }
451
452         strbuf_release(&str);
453         fclose(fp);
454 }
455
456 static char *join_sha1_array_hex(struct oid_array *array, char delim)
457 {
458         struct strbuf joined_hexs = STRBUF_INIT;
459         int i;
460
461         for (i = 0; i < array->nr; i++) {
462                 strbuf_addstr(&joined_hexs, oid_to_hex(array->oid + i));
463                 if (i + 1 < array->nr)
464                         strbuf_addch(&joined_hexs, delim);
465         }
466
467         return strbuf_detach(&joined_hexs, NULL);
468 }
469
470 /*
471  * In this function, passing a not NULL skipped_first is very special.
472  * It means that we want to know if the first commit in the list is
473  * skipped because we will want to test a commit away from it if it is
474  * indeed skipped.
475  * So if the first commit is skipped, we cannot take the shortcut to
476  * just "return list" when we find the first non skipped commit, we
477  * have to return a fully filtered list.
478  *
479  * We use (*skipped_first == -1) to mean "it has been found that the
480  * first commit is not skipped". In this case *skipped_first is set back
481  * to 0 just before the function returns.
482  */
483 struct commit_list *filter_skipped(struct commit_list *list,
484                                    struct commit_list **tried,
485                                    int show_all,
486                                    int *count,
487                                    int *skipped_first)
488 {
489         struct commit_list *filtered = NULL, **f = &filtered;
490
491         *tried = NULL;
492
493         if (skipped_first)
494                 *skipped_first = 0;
495         if (count)
496                 *count = 0;
497
498         if (!skipped_revs.nr)
499                 return list;
500
501         while (list) {
502                 struct commit_list *next = list->next;
503                 list->next = NULL;
504                 if (0 <= oid_array_lookup(&skipped_revs, &list->item->object.oid)) {
505                         if (skipped_first && !*skipped_first)
506                                 *skipped_first = 1;
507                         /* Move current to tried list */
508                         *tried = list;
509                         tried = &list->next;
510                 } else {
511                         if (!show_all) {
512                                 if (!skipped_first || !*skipped_first)
513                                         return list;
514                         } else if (skipped_first && !*skipped_first) {
515                                 /* This means we know it's not skipped */
516                                 *skipped_first = -1;
517                         }
518                         /* Move current to filtered list */
519                         *f = list;
520                         f = &list->next;
521                         if (count)
522                                 (*count)++;
523                 }
524                 list = next;
525         }
526
527         if (skipped_first && *skipped_first == -1)
528                 *skipped_first = 0;
529
530         return filtered;
531 }
532
533 #define PRN_MODULO 32768
534
535 /*
536  * This is a pseudo random number generator based on "man 3 rand".
537  * It is not used properly because the seed is the argument and it
538  * is increased by one between each call, but that should not matter
539  * for this application.
540  */
541 static unsigned get_prn(unsigned count) {
542         count = count * 1103515245 + 12345;
543         return (count/65536) % PRN_MODULO;
544 }
545
546 /*
547  * Custom integer square root from
548  * http://en.wikipedia.org/wiki/Integer_square_root
549  */
550 static int sqrti(int val)
551 {
552         float d, x = val;
553
554         if (val == 0)
555                 return 0;
556
557         do {
558                 float y = (x + (float)val / x) / 2;
559                 d = (y > x) ? y - x : x - y;
560                 x = y;
561         } while (d >= 0.5);
562
563         return (int)x;
564 }
565
566 static struct commit_list *skip_away(struct commit_list *list, int count)
567 {
568         struct commit_list *cur, *previous;
569         int prn, index, i;
570
571         prn = get_prn(count);
572         index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);
573
574         cur = list;
575         previous = NULL;
576
577         for (i = 0; cur; cur = cur->next, i++) {
578                 if (i == index) {
579                         if (oidcmp(&cur->item->object.oid, current_bad_oid))
580                                 return cur;
581                         if (previous)
582                                 return previous;
583                         return list;
584                 }
585                 previous = cur;
586         }
587
588         return list;
589 }
590
591 static struct commit_list *managed_skipped(struct commit_list *list,
592                                            struct commit_list **tried)
593 {
594         int count, skipped_first;
595
596         *tried = NULL;
597
598         if (!skipped_revs.nr)
599                 return list;
600
601         list = filter_skipped(list, tried, 0, &count, &skipped_first);
602
603         if (!skipped_first)
604                 return list;
605
606         return skip_away(list, count);
607 }
608
609 static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
610                              const char *bad_format, const char *good_format,
611                              int read_paths)
612 {
613         struct argv_array rev_argv = ARGV_ARRAY_INIT;
614         int i;
615
616         init_revisions(revs, prefix);
617         revs->abbrev = 0;
618         revs->commit_format = CMIT_FMT_UNSPECIFIED;
619
620         /* rev_argv.argv[0] will be ignored by setup_revisions */
621         argv_array_push(&rev_argv, "bisect_rev_setup");
622         argv_array_pushf(&rev_argv, bad_format, oid_to_hex(current_bad_oid));
623         for (i = 0; i < good_revs.nr; i++)
624                 argv_array_pushf(&rev_argv, good_format,
625                                  oid_to_hex(good_revs.oid + i));
626         argv_array_push(&rev_argv, "--");
627         if (read_paths)
628                 read_bisect_paths(&rev_argv);
629
630         setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
631         /* XXX leak rev_argv, as "revs" may still be pointing to it */
632 }
633
634 static void bisect_common(struct rev_info *revs)
635 {
636         if (prepare_revision_walk(revs))
637                 die("revision walk setup failed");
638         if (revs->tree_objects)
639                 mark_edges_uninteresting(revs, NULL);
640 }
641
642 static void exit_if_skipped_commits(struct commit_list *tried,
643                                     const struct object_id *bad)
644 {
645         if (!tried)
646                 return;
647
648         printf("There are only 'skip'ped commits left to test.\n"
649                "The first %s commit could be any of:\n", term_bad);
650
651         for ( ; tried; tried = tried->next)
652                 printf("%s\n", oid_to_hex(&tried->item->object.oid));
653
654         if (bad)
655                 printf("%s\n", oid_to_hex(bad));
656         printf(_("We cannot bisect more!\n"));
657         exit(2);
658 }
659
660 static int is_expected_rev(const struct object_id *oid)
661 {
662         const char *filename = git_path_bisect_expected_rev();
663         struct stat st;
664         struct strbuf str = STRBUF_INIT;
665         FILE *fp;
666         int res = 0;
667
668         if (stat(filename, &st) || !S_ISREG(st.st_mode))
669                 return 0;
670
671         fp = fopen(filename, "r");
672         if (!fp)
673                 return 0;
674
675         if (strbuf_getline_lf(&str, fp) != EOF)
676                 res = !strcmp(str.buf, oid_to_hex(oid));
677
678         strbuf_release(&str);
679         fclose(fp);
680
681         return res;
682 }
683
684 static int bisect_checkout(const unsigned char *bisect_rev, int no_checkout)
685 {
686         char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
687
688         memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
689         update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
690
691         argv_checkout[2] = bisect_rev_hex;
692         if (no_checkout) {
693                 update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
694         } else {
695                 int res;
696                 res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
697                 if (res)
698                         exit(res);
699         }
700
701         argv_show_branch[1] = bisect_rev_hex;
702         return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
703 }
704
705 static struct commit *get_commit_reference(const struct object_id *oid)
706 {
707         struct commit *r = lookup_commit_reference(oid->hash);
708         if (!r)
709                 die(_("Not a valid commit name %s"), oid_to_hex(oid));
710         return r;
711 }
712
713 static struct commit **get_bad_and_good_commits(int *rev_nr)
714 {
715         struct commit **rev;
716         int i, n = 0;
717
718         ALLOC_ARRAY(rev, 1 + good_revs.nr);
719         rev[n++] = get_commit_reference(current_bad_oid);
720         for (i = 0; i < good_revs.nr; i++)
721                 rev[n++] = get_commit_reference(good_revs.oid + i);
722         *rev_nr = n;
723
724         return rev;
725 }
726
727 static void handle_bad_merge_base(void)
728 {
729         if (is_expected_rev(current_bad_oid)) {
730                 char *bad_hex = oid_to_hex(current_bad_oid);
731                 char *good_hex = join_sha1_array_hex(&good_revs, ' ');
732                 if (!strcmp(term_bad, "bad") && !strcmp(term_good, "good")) {
733                         fprintf(stderr, _("The merge base %s is bad.\n"
734                                 "This means the bug has been fixed "
735                                 "between %s and [%s].\n"),
736                                 bad_hex, bad_hex, good_hex);
737                 } else if (!strcmp(term_bad, "new") && !strcmp(term_good, "old")) {
738                         fprintf(stderr, _("The merge base %s is new.\n"
739                                 "The property has changed "
740                                 "between %s and [%s].\n"),
741                                 bad_hex, bad_hex, good_hex);
742                 } else {
743                         fprintf(stderr, _("The merge base %s is %s.\n"
744                                 "This means the first '%s' commit is "
745                                 "between %s and [%s].\n"),
746                                 bad_hex, term_bad, term_good, bad_hex, good_hex);
747                 }
748                 exit(3);
749         }
750
751         fprintf(stderr, _("Some %s revs are not ancestors of the %s rev.\n"
752                 "git bisect cannot work properly in this case.\n"
753                 "Maybe you mistook %s and %s revs?\n"),
754                 term_good, term_bad, term_good, term_bad);
755         exit(1);
756 }
757
758 static void handle_skipped_merge_base(const struct object_id *mb)
759 {
760         char *mb_hex = oid_to_hex(mb);
761         char *bad_hex = oid_to_hex(current_bad_oid);
762         char *good_hex = join_sha1_array_hex(&good_revs, ' ');
763
764         warning(_("the merge base between %s and [%s] "
765                 "must be skipped.\n"
766                 "So we cannot be sure the first %s commit is "
767                 "between %s and %s.\n"
768                 "We continue anyway."),
769                 bad_hex, good_hex, term_bad, mb_hex, bad_hex);
770         free(good_hex);
771 }
772
773 /*
774  * "check_merge_bases" checks that merge bases are not "bad" (or "new").
775  *
776  * - If one is "bad" (or "new"), it means the user assumed something wrong
777  * and we must exit with a non 0 error code.
778  * - If one is "good" (or "old"), that's good, we have nothing to do.
779  * - If one is "skipped", we can't know but we should warn.
780  * - If we don't know, we should check it out and ask the user to test.
781  */
782 static void check_merge_bases(int no_checkout)
783 {
784         struct commit_list *result;
785         int rev_nr;
786         struct commit **rev = get_bad_and_good_commits(&rev_nr);
787
788         result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1);
789
790         for (; result; result = result->next) {
791                 const struct object_id *mb = &result->item->object.oid;
792                 if (!oidcmp(mb, current_bad_oid)) {
793                         handle_bad_merge_base();
794                 } else if (0 <= oid_array_lookup(&good_revs, mb)) {
795                         continue;
796                 } else if (0 <= oid_array_lookup(&skipped_revs, mb)) {
797                         handle_skipped_merge_base(mb);
798                 } else {
799                         printf(_("Bisecting: a merge base must be tested\n"));
800                         exit(bisect_checkout(mb->hash, no_checkout));
801                 }
802         }
803
804         free(rev);
805         free_commit_list(result);
806 }
807
808 static int check_ancestors(const char *prefix)
809 {
810         struct rev_info revs;
811         struct object_array pending_copy;
812         int res;
813
814         bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
815
816         /* Save pending objects, so they can be cleaned up later. */
817         pending_copy = revs.pending;
818         revs.leak_pending = 1;
819
820         /*
821          * bisect_common calls prepare_revision_walk right away, which
822          * (together with .leak_pending = 1) makes us the sole owner of
823          * the list of pending objects.
824          */
825         bisect_common(&revs);
826         res = (revs.commits != NULL);
827
828         /* Clean up objects used, as they will be reused. */
829         clear_commit_marks_for_object_array(&pending_copy, ALL_REV_FLAGS);
830         free(pending_copy.objects);
831
832         return res;
833 }
834
835 /*
836  * "check_good_are_ancestors_of_bad" checks that all "good" revs are
837  * ancestor of the "bad" rev.
838  *
839  * If that's not the case, we need to check the merge bases.
840  * If a merge base must be tested by the user, its source code will be
841  * checked out to be tested by the user and we will exit.
842  */
843 static void check_good_are_ancestors_of_bad(const char *prefix, int no_checkout)
844 {
845         char *filename = git_pathdup("BISECT_ANCESTORS_OK");
846         struct stat st;
847         int fd;
848
849         if (!current_bad_oid)
850                 die(_("a %s revision is needed"), term_bad);
851
852         /* Check if file BISECT_ANCESTORS_OK exists. */
853         if (!stat(filename, &st) && S_ISREG(st.st_mode))
854                 goto done;
855
856         /* Bisecting with no good rev is ok. */
857         if (good_revs.nr == 0)
858                 goto done;
859
860         /* Check if all good revs are ancestor of the bad rev. */
861         if (check_ancestors(prefix))
862                 check_merge_bases(no_checkout);
863
864         /* Create file BISECT_ANCESTORS_OK. */
865         fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
866         if (fd < 0)
867                 warning_errno(_("could not create file '%s'"),
868                               filename);
869         else
870                 close(fd);
871  done:
872         free(filename);
873 }
874
875 /*
876  * This does "git diff-tree --pretty COMMIT" without one fork+exec.
877  */
878 static void show_diff_tree(const char *prefix, struct commit *commit)
879 {
880         struct rev_info opt;
881
882         /* diff-tree init */
883         init_revisions(&opt, prefix);
884         git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
885         opt.abbrev = 0;
886         opt.diff = 1;
887
888         /* This is what "--pretty" does */
889         opt.verbose_header = 1;
890         opt.use_terminator = 0;
891         opt.commit_format = CMIT_FMT_DEFAULT;
892
893         /* diff-tree init */
894         if (!opt.diffopt.output_format)
895                 opt.diffopt.output_format = DIFF_FORMAT_RAW;
896
897         setup_revisions(0, NULL, &opt, NULL);
898         log_tree_commit(&opt, commit);
899 }
900
901 /*
902  * The terms used for this bisect session are stored in BISECT_TERMS.
903  * We read them and store them to adapt the messages accordingly.
904  * Default is bad/good.
905  */
906 void read_bisect_terms(const char **read_bad, const char **read_good)
907 {
908         struct strbuf str = STRBUF_INIT;
909         const char *filename = git_path("BISECT_TERMS");
910         FILE *fp = fopen(filename, "r");
911
912         if (!fp) {
913                 if (errno == ENOENT) {
914                         *read_bad = "bad";
915                         *read_good = "good";
916                         return;
917                 } else {
918                         die_errno(_("could not read file '%s'"), filename);
919                 }
920         } else {
921                 strbuf_getline_lf(&str, fp);
922                 *read_bad = strbuf_detach(&str, NULL);
923                 strbuf_getline_lf(&str, fp);
924                 *read_good = strbuf_detach(&str, NULL);
925         }
926         strbuf_release(&str);
927         fclose(fp);
928 }
929
930 /*
931  * We use the convention that exiting with an exit code 10 means that
932  * the bisection process finished successfully.
933  * In this case the calling shell script should exit 0.
934  *
935  * If no_checkout is non-zero, the bisection process does not
936  * checkout the trial commit but instead simply updates BISECT_HEAD.
937  */
938 int bisect_next_all(const char *prefix, int no_checkout)
939 {
940         struct rev_info revs;
941         struct commit_list *tried;
942         int reaches = 0, all = 0, nr, steps;
943         const unsigned char *bisect_rev;
944         char *steps_msg;
945
946         read_bisect_terms(&term_bad, &term_good);
947         if (read_bisect_refs())
948                 die(_("reading bisect refs failed"));
949
950         check_good_are_ancestors_of_bad(prefix, no_checkout);
951
952         bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
953         revs.limited = 1;
954
955         bisect_common(&revs);
956
957         revs.commits = find_bisection(revs.commits, &reaches, &all,
958                                        !!skipped_revs.nr);
959         revs.commits = managed_skipped(revs.commits, &tried);
960
961         if (!revs.commits) {
962                 /*
963                  * We should exit here only if the "bad"
964                  * commit is also a "skip" commit.
965                  */
966                 exit_if_skipped_commits(tried, NULL);
967
968                 printf(_("%s was both %s and %s\n"),
969                        oid_to_hex(current_bad_oid),
970                        term_good,
971                        term_bad);
972                 exit(1);
973         }
974
975         if (!all) {
976                 fprintf(stderr, _("No testable commit found.\n"
977                         "Maybe you started with bad path parameters?\n"));
978                 exit(4);
979         }
980
981         bisect_rev = revs.commits->item->object.oid.hash;
982
983         if (!hashcmp(bisect_rev, current_bad_oid->hash)) {
984                 exit_if_skipped_commits(tried, current_bad_oid);
985                 printf("%s is the first %s commit\n", sha1_to_hex(bisect_rev),
986                         term_bad);
987                 show_diff_tree(prefix, revs.commits->item);
988                 /* This means the bisection process succeeded. */
989                 exit(10);
990         }
991
992         nr = all - reaches - 1;
993         steps = estimate_bisect_steps(all);
994
995         steps_msg = xstrfmt(Q_("(roughly %d step)", "(roughly %d steps)",
996                   steps), steps);
997         /* TRANSLATORS: the last %s will be replaced with
998            "(roughly %d steps)" translation */
999         printf(Q_("Bisecting: %d revision left to test after this %s\n",
1000                   "Bisecting: %d revisions left to test after this %s\n",
1001                   nr), nr, steps_msg);
1002         free(steps_msg);
1003
1004         return bisect_checkout(bisect_rev, no_checkout);
1005 }
1006
1007 static inline int log2i(int n)
1008 {
1009         int log2 = 0;
1010
1011         for (; n > 1; n >>= 1)
1012                 log2++;
1013
1014         return log2;
1015 }
1016
1017 static inline int exp2i(int n)
1018 {
1019         return 1 << n;
1020 }
1021
1022 /*
1023  * Estimate the number of bisect steps left (after the current step)
1024  *
1025  * For any x between 0 included and 2^n excluded, the probability for
1026  * n - 1 steps left looks like:
1027  *
1028  * P(2^n + x) == (2^n - x) / (2^n + x)
1029  *
1030  * and P(2^n + x) < 0.5 means 2^n < 3x
1031  */
1032 int estimate_bisect_steps(int all)
1033 {
1034         int n, x, e;
1035
1036         if (all < 3)
1037                 return 0;
1038
1039         n = log2i(all);
1040         e = exp2i(n);
1041         x = all - e;
1042
1043         return (e < 3 * x) ? n : n - 1;
1044 }