Merge branch 'ew/svn-branch-segfault-fix' into maint
[git] / bisect.c
1 #include "cache.h"
2 #include "config.h"
3 #include "commit.h"
4 #include "diff.h"
5 #include "revision.h"
6 #include "refs.h"
7 #include "list-objects.h"
8 #include "quote.h"
9 #include "sha1-lookup.h"
10 #include "run-command.h"
11 #include "log-tree.h"
12 #include "bisect.h"
13 #include "sha1-array.h"
14 #include "argv-array.h"
15
16 static struct oid_array good_revs;
17 static struct oid_array skipped_revs;
18
19 static struct object_id *current_bad_oid;
20
21 static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
22 static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
23
24 static const char *term_bad;
25 static const char *term_good;
26
27 /* Remember to update object flag allocation in object.h */
28 #define COUNTED         (1u<<16)
29
30 /*
31  * This is a truly stupid algorithm, but it's only
32  * used for bisection, and we just don't care enough.
33  *
34  * We care just barely enough to avoid recursing for
35  * non-merge entries.
36  */
37 static int count_distance(struct commit_list *entry)
38 {
39         int nr = 0;
40
41         while (entry) {
42                 struct commit *commit = entry->item;
43                 struct commit_list *p;
44
45                 if (commit->object.flags & (UNINTERESTING | COUNTED))
46                         break;
47                 if (!(commit->object.flags & TREESAME))
48                         nr++;
49                 commit->object.flags |= COUNTED;
50                 p = commit->parents;
51                 entry = p;
52                 if (p) {
53                         p = p->next;
54                         while (p) {
55                                 nr += count_distance(p);
56                                 p = p->next;
57                         }
58                 }
59         }
60
61         return nr;
62 }
63
64 static void clear_distance(struct commit_list *list)
65 {
66         while (list) {
67                 struct commit *commit = list->item;
68                 commit->object.flags &= ~COUNTED;
69                 list = list->next;
70         }
71 }
72
73 #define DEBUG_BISECT 0
74
75 static inline int weight(struct commit_list *elem)
76 {
77         return *((int*)(elem->item->util));
78 }
79
80 static inline void weight_set(struct commit_list *elem, int weight)
81 {
82         *((int*)(elem->item->util)) = weight;
83 }
84
85 static int count_interesting_parents(struct commit *commit)
86 {
87         struct commit_list *p;
88         int count;
89
90         for (count = 0, p = commit->parents; p; p = p->next) {
91                 if (p->item->object.flags & UNINTERESTING)
92                         continue;
93                 count++;
94         }
95         return count;
96 }
97
98 static inline int halfway(struct commit_list *p, int nr)
99 {
100         /*
101          * Don't short-cut something we are not going to return!
102          */
103         if (p->item->object.flags & TREESAME)
104                 return 0;
105         if (DEBUG_BISECT)
106                 return 0;
107         /*
108          * 2 and 3 are halfway of 5.
109          * 3 is halfway of 6 but 2 and 4 are not.
110          */
111         switch (2 * weight(p) - nr) {
112         case -1: case 0: case 1:
113                 return 1;
114         default:
115                 return 0;
116         }
117 }
118
119 #if !DEBUG_BISECT
120 #define show_list(a,b,c,d) do { ; } while (0)
121 #else
122 static void show_list(const char *debug, int counted, int nr,
123                       struct commit_list *list)
124 {
125         struct commit_list *p;
126
127         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
128
129         for (p = list; p; p = p->next) {
130                 struct commit_list *pp;
131                 struct commit *commit = p->item;
132                 unsigned flags = commit->object.flags;
133                 enum object_type type;
134                 unsigned long size;
135                 char *buf = read_sha1_file(commit->object.oid.hash, &type, &size);
136                 const char *subject_start;
137                 int subject_len;
138
139                 fprintf(stderr, "%c%c%c ",
140                         (flags & TREESAME) ? ' ' : 'T',
141                         (flags & UNINTERESTING) ? 'U' : ' ',
142                         (flags & COUNTED) ? 'C' : ' ');
143                 if (commit->util)
144                         fprintf(stderr, "%3d", weight(p));
145                 else
146                         fprintf(stderr, "---");
147                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.oid.hash));
148                 for (pp = commit->parents; pp; pp = pp->next)
149                         fprintf(stderr, " %.*s", 8,
150                                 sha1_to_hex(pp->item->object.oid.hash));
151
152                 subject_len = find_commit_subject(buf, &subject_start);
153                 if (subject_len)
154                         fprintf(stderr, " %.*s", subject_len, subject_start);
155                 fprintf(stderr, "\n");
156         }
157 }
158 #endif /* DEBUG_BISECT */
159
160 static struct commit_list *best_bisection(struct commit_list *list, int nr)
161 {
162         struct commit_list *p, *best;
163         int best_distance = -1;
164
165         best = list;
166         for (p = list; p; p = p->next) {
167                 int distance;
168                 unsigned flags = p->item->object.flags;
169
170                 if (flags & TREESAME)
171                         continue;
172                 distance = weight(p);
173                 if (nr - distance < distance)
174                         distance = nr - distance;
175                 if (distance > best_distance) {
176                         best = p;
177                         best_distance = distance;
178                 }
179         }
180
181         return best;
182 }
183
184 struct commit_dist {
185         struct commit *commit;
186         int distance;
187 };
188
189 static int compare_commit_dist(const void *a_, const void *b_)
190 {
191         struct commit_dist *a, *b;
192
193         a = (struct commit_dist *)a_;
194         b = (struct commit_dist *)b_;
195         if (a->distance != b->distance)
196                 return b->distance - a->distance; /* desc sort */
197         return oidcmp(&a->commit->object.oid, &b->commit->object.oid);
198 }
199
200 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
201 {
202         struct commit_list *p;
203         struct commit_dist *array = xcalloc(nr, sizeof(*array));
204         struct strbuf buf = STRBUF_INIT;
205         int cnt, i;
206
207         for (p = list, cnt = 0; p; p = p->next) {
208                 int distance;
209                 unsigned flags = p->item->object.flags;
210
211                 if (flags & TREESAME)
212                         continue;
213                 distance = weight(p);
214                 if (nr - distance < distance)
215                         distance = nr - distance;
216                 array[cnt].commit = p->item;
217                 array[cnt].distance = distance;
218                 cnt++;
219         }
220         QSORT(array, cnt, compare_commit_dist);
221         for (p = list, i = 0; i < cnt; i++) {
222                 struct object *obj = &(array[i].commit->object);
223
224                 strbuf_reset(&buf);
225                 strbuf_addf(&buf, "dist=%d", array[i].distance);
226                 add_name_decoration(DECORATION_NONE, buf.buf, obj);
227
228                 p->item = array[i].commit;
229                 if (i < cnt - 1)
230                         p = p->next;
231         }
232         if (p) {
233                 free_commit_list(p->next);
234                 p->next = NULL;
235         }
236         strbuf_release(&buf);
237         free(array);
238         return list;
239 }
240
241 /*
242  * zero or positive weight is the number of interesting commits it can
243  * reach, including itself.  Especially, weight = 0 means it does not
244  * reach any tree-changing commits (e.g. just above uninteresting one
245  * but traversal is with pathspec).
246  *
247  * weight = -1 means it has one parent and its distance is yet to
248  * be computed.
249  *
250  * weight = -2 means it has more than one parent and its distance is
251  * unknown.  After running count_distance() first, they will get zero
252  * or positive distance.
253  */
254 static struct commit_list *do_find_bisection(struct commit_list *list,
255                                              int nr, int *weights,
256                                              int find_all)
257 {
258         int n, counted;
259         struct commit_list *p;
260
261         counted = 0;
262
263         for (n = 0, p = list; p; p = p->next) {
264                 struct commit *commit = p->item;
265                 unsigned flags = commit->object.flags;
266
267                 p->item->util = &weights[n++];
268                 switch (count_interesting_parents(commit)) {
269                 case 0:
270                         if (!(flags & TREESAME)) {
271                                 weight_set(p, 1);
272                                 counted++;
273                                 show_list("bisection 2 count one",
274                                           counted, nr, list);
275                         }
276                         /*
277                          * otherwise, it is known not to reach any
278                          * tree-changing commit and gets weight 0.
279                          */
280                         break;
281                 case 1:
282                         weight_set(p, -1);
283                         break;
284                 default:
285                         weight_set(p, -2);
286                         break;
287                 }
288         }
289
290         show_list("bisection 2 initialize", counted, nr, list);
291
292         /*
293          * If you have only one parent in the resulting set
294          * then you can reach one commit more than that parent
295          * can reach.  So we do not have to run the expensive
296          * count_distance() for single strand of pearls.
297          *
298          * However, if you have more than one parents, you cannot
299          * just add their distance and one for yourself, since
300          * they usually reach the same ancestor and you would
301          * end up counting them twice that way.
302          *
303          * So we will first count distance of merges the usual
304          * way, and then fill the blanks using cheaper algorithm.
305          */
306         for (p = list; p; p = p->next) {
307                 if (p->item->object.flags & UNINTERESTING)
308                         continue;
309                 if (weight(p) != -2)
310                         continue;
311                 weight_set(p, count_distance(p));
312                 clear_distance(list);
313
314                 /* Does it happen to be at exactly half-way? */
315                 if (!find_all && halfway(p, nr))
316                         return p;
317                 counted++;
318         }
319
320         show_list("bisection 2 count_distance", counted, nr, list);
321
322         while (counted < nr) {
323                 for (p = list; p; p = p->next) {
324                         struct commit_list *q;
325                         unsigned flags = p->item->object.flags;
326
327                         if (0 <= weight(p))
328                                 continue;
329                         for (q = p->item->parents; q; q = q->next) {
330                                 if (q->item->object.flags & UNINTERESTING)
331                                         continue;
332                                 if (0 <= weight(q))
333                                         break;
334                         }
335                         if (!q)
336                                 continue;
337
338                         /*
339                          * weight for p is unknown but q is known.
340                          * add one for p itself if p is to be counted,
341                          * otherwise inherit it from q directly.
342                          */
343                         if (!(flags & TREESAME)) {
344                                 weight_set(p, weight(q)+1);
345                                 counted++;
346                                 show_list("bisection 2 count one",
347                                           counted, nr, list);
348                         }
349                         else
350                                 weight_set(p, weight(q));
351
352                         /* Does it happen to be at exactly half-way? */
353                         if (!find_all && halfway(p, nr))
354                                 return p;
355                 }
356         }
357
358         show_list("bisection 2 counted all", counted, nr, list);
359
360         if (!find_all)
361                 return best_bisection(list, nr);
362         else
363                 return best_bisection_sorted(list, nr);
364 }
365
366 void find_bisection(struct commit_list **commit_list, int *reaches,
367                     int *all, int find_all)
368 {
369         int nr, on_list;
370         struct commit_list *list, *p, *best, *next, *last;
371         int *weights;
372
373         show_list("bisection 2 entry", 0, 0, *commit_list);
374
375         /*
376          * Count the number of total and tree-changing items on the
377          * list, while reversing the list.
378          */
379         for (nr = on_list = 0, last = NULL, p = *commit_list;
380              p;
381              p = next) {
382                 unsigned flags = p->item->object.flags;
383
384                 next = p->next;
385                 if (flags & UNINTERESTING) {
386                         free(p);
387                         continue;
388                 }
389                 p->next = last;
390                 last = p;
391                 if (!(flags & TREESAME))
392                         nr++;
393                 on_list++;
394         }
395         list = last;
396         show_list("bisection 2 sorted", 0, nr, list);
397
398         *all = nr;
399         weights = xcalloc(on_list, sizeof(*weights));
400
401         /* Do the real work of finding bisection commit. */
402         best = do_find_bisection(list, nr, weights, find_all);
403         if (best) {
404                 if (!find_all) {
405                         list->item = best->item;
406                         free_commit_list(list->next);
407                         best = list;
408                         best->next = NULL;
409                 }
410                 *reaches = weight(best);
411         }
412         free(weights);
413         *commit_list = best;
414 }
415
416 static int register_ref(const char *refname, const struct object_id *oid,
417                         int flags, void *cb_data)
418 {
419         struct strbuf good_prefix = STRBUF_INIT;
420         strbuf_addstr(&good_prefix, term_good);
421         strbuf_addstr(&good_prefix, "-");
422
423         if (!strcmp(refname, term_bad)) {
424                 current_bad_oid = xmalloc(sizeof(*current_bad_oid));
425                 oidcpy(current_bad_oid, oid);
426         } else if (starts_with(refname, good_prefix.buf)) {
427                 oid_array_append(&good_revs, oid);
428         } else if (starts_with(refname, "skip-")) {
429                 oid_array_append(&skipped_revs, oid);
430         }
431
432         strbuf_release(&good_prefix);
433
434         return 0;
435 }
436
437 static int read_bisect_refs(void)
438 {
439         return for_each_ref_in("refs/bisect/", register_ref, NULL);
440 }
441
442 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
443 static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
444 static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
445 static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
446 static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
447 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
448 static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
449 static GIT_PATH_FUNC(git_path_head_name, "head-name")
450
451 static void read_bisect_paths(struct argv_array *array)
452 {
453         struct strbuf str = STRBUF_INIT;
454         const char *filename = git_path_bisect_names();
455         FILE *fp = xfopen(filename, "r");
456
457         while (strbuf_getline_lf(&str, fp) != EOF) {
458                 strbuf_trim(&str);
459                 if (sq_dequote_to_argv_array(str.buf, array))
460                         die(_("Badly quoted content in file '%s': %s"),
461                             filename, str.buf);
462         }
463
464         strbuf_release(&str);
465         fclose(fp);
466 }
467
468 static char *join_sha1_array_hex(struct oid_array *array, char delim)
469 {
470         struct strbuf joined_hexs = STRBUF_INIT;
471         int i;
472
473         for (i = 0; i < array->nr; i++) {
474                 strbuf_addstr(&joined_hexs, oid_to_hex(array->oid + i));
475                 if (i + 1 < array->nr)
476                         strbuf_addch(&joined_hexs, delim);
477         }
478
479         return strbuf_detach(&joined_hexs, NULL);
480 }
481
482 /*
483  * In this function, passing a not NULL skipped_first is very special.
484  * It means that we want to know if the first commit in the list is
485  * skipped because we will want to test a commit away from it if it is
486  * indeed skipped.
487  * So if the first commit is skipped, we cannot take the shortcut to
488  * just "return list" when we find the first non skipped commit, we
489  * have to return a fully filtered list.
490  *
491  * We use (*skipped_first == -1) to mean "it has been found that the
492  * first commit is not skipped". In this case *skipped_first is set back
493  * to 0 just before the function returns.
494  */
495 struct commit_list *filter_skipped(struct commit_list *list,
496                                    struct commit_list **tried,
497                                    int show_all,
498                                    int *count,
499                                    int *skipped_first)
500 {
501         struct commit_list *filtered = NULL, **f = &filtered;
502
503         *tried = NULL;
504
505         if (skipped_first)
506                 *skipped_first = 0;
507         if (count)
508                 *count = 0;
509
510         if (!skipped_revs.nr)
511                 return list;
512
513         while (list) {
514                 struct commit_list *next = list->next;
515                 list->next = NULL;
516                 if (0 <= oid_array_lookup(&skipped_revs, &list->item->object.oid)) {
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 unsigned get_prn(unsigned count) {
554         count = count * 1103515245 + 12345;
555         return (count/65536) % PRN_MODULO;
556 }
557
558 /*
559  * Custom integer square root from
560  * https://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 (oidcmp(&cur->item->object.oid, current_bad_oid))
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 = ARGV_ARRAY_INIT;
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, "bisect_rev_setup");
634         argv_array_pushf(&rev_argv, bad_format, oid_to_hex(current_bad_oid));
635         for (i = 0; i < good_revs.nr; i++)
636                 argv_array_pushf(&rev_argv, good_format,
637                                  oid_to_hex(good_revs.oid + i));
638         argv_array_push(&rev_argv, "--");
639         if (read_paths)
640                 read_bisect_paths(&rev_argv);
641
642         setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
643         /* XXX leak rev_argv, as "revs" may still be pointing to it */
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, NULL);
652 }
653
654 static void exit_if_skipped_commits(struct commit_list *tried,
655                                     const struct object_id *bad)
656 {
657         if (!tried)
658                 return;
659
660         printf("There are only 'skip'ped commits left to test.\n"
661                "The first %s commit could be any of:\n", term_bad);
662
663         for ( ; tried; tried = tried->next)
664                 printf("%s\n", oid_to_hex(&tried->item->object.oid));
665
666         if (bad)
667                 printf("%s\n", oid_to_hex(bad));
668         printf(_("We cannot bisect more!\n"));
669         exit(2);
670 }
671
672 static int is_expected_rev(const struct object_id *oid)
673 {
674         const char *filename = git_path_bisect_expected_rev();
675         struct stat st;
676         struct strbuf str = STRBUF_INIT;
677         FILE *fp;
678         int res = 0;
679
680         if (stat(filename, &st) || !S_ISREG(st.st_mode))
681                 return 0;
682
683         fp = fopen_or_warn(filename, "r");
684         if (!fp)
685                 return 0;
686
687         if (strbuf_getline_lf(&str, fp) != EOF)
688                 res = !strcmp(str.buf, oid_to_hex(oid));
689
690         strbuf_release(&str);
691         fclose(fp);
692
693         return res;
694 }
695
696 static int bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
697 {
698         char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
699
700         memcpy(bisect_rev_hex, oid_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
701         update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
702
703         argv_checkout[2] = bisect_rev_hex;
704         if (no_checkout) {
705                 update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0,
706                            UPDATE_REFS_DIE_ON_ERR);
707         } else {
708                 int res;
709                 res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
710                 if (res)
711                         exit(res);
712         }
713
714         argv_show_branch[1] = bisect_rev_hex;
715         return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
716 }
717
718 static struct commit *get_commit_reference(const struct object_id *oid)
719 {
720         struct commit *r = lookup_commit_reference(oid);
721         if (!r)
722                 die(_("Not a valid commit name %s"), oid_to_hex(oid));
723         return r;
724 }
725
726 static struct commit **get_bad_and_good_commits(int *rev_nr)
727 {
728         struct commit **rev;
729         int i, n = 0;
730
731         ALLOC_ARRAY(rev, 1 + good_revs.nr);
732         rev[n++] = get_commit_reference(current_bad_oid);
733         for (i = 0; i < good_revs.nr; i++)
734                 rev[n++] = get_commit_reference(good_revs.oid + i);
735         *rev_nr = n;
736
737         return rev;
738 }
739
740 static void handle_bad_merge_base(void)
741 {
742         if (is_expected_rev(current_bad_oid)) {
743                 char *bad_hex = oid_to_hex(current_bad_oid);
744                 char *good_hex = join_sha1_array_hex(&good_revs, ' ');
745                 if (!strcmp(term_bad, "bad") && !strcmp(term_good, "good")) {
746                         fprintf(stderr, _("The merge base %s is bad.\n"
747                                 "This means the bug has been fixed "
748                                 "between %s and [%s].\n"),
749                                 bad_hex, bad_hex, good_hex);
750                 } else if (!strcmp(term_bad, "new") && !strcmp(term_good, "old")) {
751                         fprintf(stderr, _("The merge base %s is new.\n"
752                                 "The property has changed "
753                                 "between %s and [%s].\n"),
754                                 bad_hex, bad_hex, good_hex);
755                 } else {
756                         fprintf(stderr, _("The merge base %s is %s.\n"
757                                 "This means the first '%s' commit is "
758                                 "between %s and [%s].\n"),
759                                 bad_hex, term_bad, term_good, bad_hex, good_hex);
760                 }
761                 exit(3);
762         }
763
764         fprintf(stderr, _("Some %s revs are not ancestors of the %s rev.\n"
765                 "git bisect cannot work properly in this case.\n"
766                 "Maybe you mistook %s and %s revs?\n"),
767                 term_good, term_bad, term_good, term_bad);
768         exit(1);
769 }
770
771 static void handle_skipped_merge_base(const struct object_id *mb)
772 {
773         char *mb_hex = oid_to_hex(mb);
774         char *bad_hex = oid_to_hex(current_bad_oid);
775         char *good_hex = join_sha1_array_hex(&good_revs, ' ');
776
777         warning(_("the merge base between %s and [%s] "
778                 "must be skipped.\n"
779                 "So we cannot be sure the first %s commit is "
780                 "between %s and %s.\n"
781                 "We continue anyway."),
782                 bad_hex, good_hex, term_bad, mb_hex, bad_hex);
783         free(good_hex);
784 }
785
786 /*
787  * "check_merge_bases" checks that merge bases are not "bad" (or "new").
788  *
789  * - If one is "bad" (or "new"), it means the user assumed something wrong
790  * and we must exit with a non 0 error code.
791  * - If one is "good" (or "old"), that's good, we have nothing to do.
792  * - If one is "skipped", we can't know but we should warn.
793  * - If we don't know, we should check it out and ask the user to test.
794  */
795 static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
796 {
797         struct commit_list *result;
798
799         result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1);
800
801         for (; result; result = result->next) {
802                 const struct object_id *mb = &result->item->object.oid;
803                 if (!oidcmp(mb, current_bad_oid)) {
804                         handle_bad_merge_base();
805                 } else if (0 <= oid_array_lookup(&good_revs, mb)) {
806                         continue;
807                 } else if (0 <= oid_array_lookup(&skipped_revs, mb)) {
808                         handle_skipped_merge_base(mb);
809                 } else {
810                         printf(_("Bisecting: a merge base must be tested\n"));
811                         exit(bisect_checkout(mb, no_checkout));
812                 }
813         }
814
815         free_commit_list(result);
816 }
817
818 static int check_ancestors(int rev_nr, struct commit **rev, const char *prefix)
819 {
820         struct rev_info revs;
821         int res;
822
823         bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
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_many(rev_nr, rev, ALL_REV_FLAGS);
830
831         return res;
832 }
833
834 /*
835  * "check_good_are_ancestors_of_bad" checks that all "good" revs are
836  * ancestor of the "bad" rev.
837  *
838  * If that's not the case, we need to check the merge bases.
839  * If a merge base must be tested by the user, its source code will be
840  * checked out to be tested by the user and we will exit.
841  */
842 static void check_good_are_ancestors_of_bad(const char *prefix, int no_checkout)
843 {
844         char *filename = git_pathdup("BISECT_ANCESTORS_OK");
845         struct stat st;
846         int fd, rev_nr;
847         struct commit **rev;
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         rev = get_bad_and_good_commits(&rev_nr);
862         if (check_ancestors(rev_nr, rev, prefix))
863                 check_merge_bases(rev_nr, rev, no_checkout);
864         free(rev);
865
866         /* Create file BISECT_ANCESTORS_OK. */
867         fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
868         if (fd < 0)
869                 warning_errno(_("could not create file '%s'"),
870                               filename);
871         else
872                 close(fd);
873  done:
874         free(filename);
875 }
876
877 /*
878  * This does "git diff-tree --pretty COMMIT" without one fork+exec.
879  */
880 static void show_diff_tree(const char *prefix, struct commit *commit)
881 {
882         struct rev_info opt;
883
884         /* diff-tree init */
885         init_revisions(&opt, prefix);
886         git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
887         opt.abbrev = 0;
888         opt.diff = 1;
889
890         /* This is what "--pretty" does */
891         opt.verbose_header = 1;
892         opt.use_terminator = 0;
893         opt.commit_format = CMIT_FMT_DEFAULT;
894
895         /* diff-tree init */
896         if (!opt.diffopt.output_format)
897                 opt.diffopt.output_format = DIFF_FORMAT_RAW;
898
899         setup_revisions(0, NULL, &opt, NULL);
900         log_tree_commit(&opt, commit);
901 }
902
903 /*
904  * The terms used for this bisect session are stored in BISECT_TERMS.
905  * We read them and store them to adapt the messages accordingly.
906  * Default is bad/good.
907  */
908 void read_bisect_terms(const char **read_bad, const char **read_good)
909 {
910         struct strbuf str = STRBUF_INIT;
911         const char *filename = git_path_bisect_terms();
912         FILE *fp = fopen(filename, "r");
913
914         if (!fp) {
915                 if (errno == ENOENT) {
916                         *read_bad = "bad";
917                         *read_good = "good";
918                         return;
919                 } else {
920                         die_errno(_("could not read file '%s'"), filename);
921                 }
922         } else {
923                 strbuf_getline_lf(&str, fp);
924                 *read_bad = strbuf_detach(&str, NULL);
925                 strbuf_getline_lf(&str, fp);
926                 *read_good = strbuf_detach(&str, NULL);
927         }
928         strbuf_release(&str);
929         fclose(fp);
930 }
931
932 /*
933  * We use the convention that exiting with an exit code 10 means that
934  * the bisection process finished successfully.
935  * In this case the calling shell script should exit 0.
936  *
937  * If no_checkout is non-zero, the bisection process does not
938  * checkout the trial commit but instead simply updates BISECT_HEAD.
939  */
940 int bisect_next_all(const char *prefix, int no_checkout)
941 {
942         struct rev_info revs;
943         struct commit_list *tried;
944         int reaches = 0, all = 0, nr, steps;
945         struct object_id *bisect_rev;
946         char *steps_msg;
947
948         read_bisect_terms(&term_bad, &term_good);
949         if (read_bisect_refs())
950                 die(_("reading bisect refs failed"));
951
952         check_good_are_ancestors_of_bad(prefix, no_checkout);
953
954         bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
955         revs.limited = 1;
956
957         bisect_common(&revs);
958
959         find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
960         revs.commits = managed_skipped(revs.commits, &tried);
961
962         if (!revs.commits) {
963                 /*
964                  * We should exit here only if the "bad"
965                  * commit is also a "skip" commit.
966                  */
967                 exit_if_skipped_commits(tried, NULL);
968
969                 printf(_("%s was both %s and %s\n"),
970                        oid_to_hex(current_bad_oid),
971                        term_good,
972                        term_bad);
973                 exit(1);
974         }
975
976         if (!all) {
977                 fprintf(stderr, _("No testable commit found.\n"
978                         "Maybe you started with bad path parameters?\n"));
979                 exit(4);
980         }
981
982         bisect_rev = &revs.commits->item->object.oid;
983
984         if (!oidcmp(bisect_rev, current_bad_oid)) {
985                 exit_if_skipped_commits(tried, current_bad_oid);
986                 printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
987                         term_bad);
988                 show_diff_tree(prefix, revs.commits->item);
989                 /* This means the bisection process succeeded. */
990                 exit(10);
991         }
992
993         nr = all - reaches - 1;
994         steps = estimate_bisect_steps(all);
995
996         steps_msg = xstrfmt(Q_("(roughly %d step)", "(roughly %d steps)",
997                   steps), steps);
998         /*
999          * TRANSLATORS: the last %s will be replaced with "(roughly %d
1000          * steps)" translation.
1001          */
1002         printf(Q_("Bisecting: %d revision left to test after this %s\n",
1003                   "Bisecting: %d revisions left to test after this %s\n",
1004                   nr), nr, steps_msg);
1005         free(steps_msg);
1006
1007         return bisect_checkout(bisect_rev, no_checkout);
1008 }
1009
1010 static inline int log2i(int n)
1011 {
1012         int log2 = 0;
1013
1014         for (; n > 1; n >>= 1)
1015                 log2++;
1016
1017         return log2;
1018 }
1019
1020 static inline int exp2i(int n)
1021 {
1022         return 1 << n;
1023 }
1024
1025 /*
1026  * Estimate the number of bisect steps left (after the current step)
1027  *
1028  * For any x between 0 included and 2^n excluded, the probability for
1029  * n - 1 steps left looks like:
1030  *
1031  * P(2^n + x) == (2^n - x) / (2^n + x)
1032  *
1033  * and P(2^n + x) < 0.5 means 2^n < 3x
1034  */
1035 int estimate_bisect_steps(int all)
1036 {
1037         int n, x, e;
1038
1039         if (all < 3)
1040                 return 0;
1041
1042         n = log2i(all);
1043         e = exp2i(n);
1044         x = all - e;
1045
1046         return (e < 3 * x) ? n : n - 1;
1047 }
1048
1049 static int mark_for_removal(const char *refname, const struct object_id *oid,
1050                             int flag, void *cb_data)
1051 {
1052         struct string_list *refs = cb_data;
1053         char *ref = xstrfmt("refs/bisect%s", refname);
1054         string_list_append(refs, ref);
1055         return 0;
1056 }
1057
1058 int bisect_clean_state(void)
1059 {
1060         int result = 0;
1061
1062         /* There may be some refs packed during bisection */
1063         struct string_list refs_for_removal = STRING_LIST_INIT_NODUP;
1064         for_each_ref_in("refs/bisect", mark_for_removal, (void *) &refs_for_removal);
1065         string_list_append(&refs_for_removal, xstrdup("BISECT_HEAD"));
1066         result = delete_refs("bisect: remove", &refs_for_removal, REF_NO_DEREF);
1067         refs_for_removal.strdup_strings = 1;
1068         string_list_clear(&refs_for_removal, 0);
1069         unlink_or_warn(git_path_bisect_expected_rev());
1070         unlink_or_warn(git_path_bisect_ancestors_ok());
1071         unlink_or_warn(git_path_bisect_log());
1072         unlink_or_warn(git_path_bisect_names());
1073         unlink_or_warn(git_path_bisect_run());
1074         unlink_or_warn(git_path_bisect_terms());
1075         /* Cleanup head-name if it got left by an old version of git-bisect */
1076         unlink_or_warn(git_path_head_name());
1077         /*
1078          * Cleanup BISECT_START last to support the --no-checkout option
1079          * introduced in the commit 4796e823a.
1080          */
1081         unlink_or_warn(git_path_bisect_start());
1082
1083         return result;
1084 }