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_object_file(&commit->object.oid, &type,
 136                                              &size);
 137                 const char *subject_start;
 138                 int subject_len;
 139
 140                 fprintf(stderr, "%c%c%c ",
 141                         (flags & TREESAME) ? ' ' : 'T',
 142                         (flags & UNINTERESTING) ? 'U' : ' ',
 143                         (flags & COUNTED) ? 'C' : ' ');
 144                 if (commit->util)
 145                         fprintf(stderr, "%3d", weight(p));
 146                 else
 147                         fprintf(stderr, "---");
 148                 fprintf(stderr, " %.*s", 8, oid_to_hex(&commit->object.oid));
 149                 for (pp = commit->parents; pp; pp = pp->next)
 150                         fprintf(stderr, " %.*s", 8,
 151                                 oid_to_hex(&pp->item->object.oid));
 152
 153                 subject_len = find_commit_subject(buf, &subject_start);
 154                 if (subject_len)
 155                         fprintf(stderr, " %.*s", subject_len, subject_start);
 156                 fprintf(stderr, "\n");
 157         }
 158 }
 159 #endif /* DEBUG_BISECT */
 160
 161 static struct commit_list *best_bisection(struct commit_list *list, int nr)
 162 {
 163         struct commit_list *p, *best;
 164         int best_distance = -1;
 165
 166         best = list;
 167         for (p = list; p; p = p->next) {
 168                 int distance;
 169                 unsigned flags = p->item->object.flags;
 170
 171                 if (flags & TREESAME)
 172                         continue;
 173                 distance = weight(p);
 174                 if (nr - distance < distance)
 175                         distance = nr - distance;
 176                 if (distance > best_distance) {
 177                         best = p;
 178                         best_distance = distance;
 179                 }
 180         }
 181
 182         return best;
 183 }
 184
 185 struct commit_dist {
 186         struct commit *commit;
 187         int distance;
 188 };
 189
 190 static int compare_commit_dist(const void *a_, const void *b_)
 191 {
 192         struct commit_dist *a, *b;
 193
 194         a = (struct commit_dist *)a_;
 195         b = (struct commit_dist *)b_;
 196         if (a->distance != b->distance)
 197                 return b->distance - a->distance; /* desc sort */
 198         return oidcmp(&a->commit->object.oid, &b->commit->object.oid);
 199 }
 200
 201 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
 202 {
 203         struct commit_list *p;
 204         struct commit_dist *array = xcalloc(nr, sizeof(*array));
 205         struct strbuf buf = STRBUF_INIT;
 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, compare_commit_dist);
 222         for (p = list, i = 0; i < cnt; i++) {
 223                 struct object *obj = &(array[i].commit->object);
 224
 225                 strbuf_reset(&buf);
 226                 strbuf_addf(&buf, "dist=%d", array[i].distance);
 227                 add_name_decoration(DECORATION_NONE, buf.buf, obj);
 228
 229                 p->item = array[i].commit;
 230                 if (i < cnt - 1)
 231                         p = p->next;
 232         }
 233         if (p) {
 234                 free_commit_list(p->next);
 235                 p->next = NULL;
 236         }
 237         strbuf_release(&buf);
 238         free(array);
 239         return list;
 240 }
 241
 242 /*
 243  * zero or positive weight is the number of interesting commits it can
 244  * reach, including itself.  Especially, weight = 0 means it does not
 245  * reach any tree-changing commits (e.g. just above uninteresting one
 246  * but traversal is with pathspec).
 247  *
 248  * weight = -1 means it has one parent and its distance is yet to
 249  * be computed.
 250  *
 251  * weight = -2 means it has more than one parent and its distance is
 252  * unknown.  After running count_distance() first, they will get zero
 253  * or positive distance.
 254  */
 255 static struct commit_list *do_find_bisection(struct commit_list *list,
 256                                              int nr, int *weights,
 257                                              int find_all)
 258 {
 259         int n, counted;
 260         struct commit_list *p;
 261
 262         counted = 0;
 263
 264         for (n = 0, p = list; p; p = p->next) {
 265                 struct commit *commit = p->item;
 266                 unsigned flags = commit->object.flags;
 267
 268                 p->item->util = &weights[n++];
 269                 switch (count_interesting_parents(commit)) {
 270                 case 0:
 271                         if (!(flags & TREESAME)) {
 272                                 weight_set(p, 1);
 273                                 counted++;
 274                                 show_list("bisection 2 count one",
 275                                           counted, nr, list);
 276                         }
 277                         /*
 278                          * otherwise, it is known not to reach any
 279                          * tree-changing commit and gets weight 0.
 280                          */
 281                         break;
 282                 case 1:
 283                         weight_set(p, -1);
 284                         break;
 285                 default:
 286                         weight_set(p, -2);
 287                         break;
 288                 }
 289         }
 290
 291         show_list("bisection 2 initialize", counted, nr, list);
 292
 293         /*
 294          * If you have only one parent in the resulting set
 295          * then you can reach one commit more than that parent
 296          * can reach.  So we do not have to run the expensive
 297          * count_distance() for single strand of pearls.
 298          *
 299          * However, if you have more than one parents, you cannot
 300          * just add their distance and one for yourself, since
 301          * they usually reach the same ancestor and you would
 302          * end up counting them twice that way.
 303          *
 304          * So we will first count distance of merges the usual
 305          * way, and then fill the blanks using cheaper algorithm.
 306          */
 307         for (p = list; p; p = p->next) {
 308                 if (p->item->object.flags & UNINTERESTING)
 309                         continue;
 310                 if (weight(p) != -2)
 311                         continue;
 312                 weight_set(p, count_distance(p));
 313                 clear_distance(list);
 314
 315                 /* Does it happen to be at exactly half-way? */
 316                 if (!find_all && halfway(p, nr))
 317                         return p;
 318                 counted++;
 319         }
 320
 321         show_list("bisection 2 count_distance", counted, nr, list);
 322
 323         while (counted < nr) {
 324                 for (p = list; p; p = p->next) {
 325                         struct commit_list *q;
 326                         unsigned flags = p->item->object.flags;
 327
 328                         if (0 <= weight(p))
 329                                 continue;
 330                         for (q = p->item->parents; q; q = q->next) {
 331                                 if (q->item->object.flags & UNINTERESTING)
 332                                         continue;
 333                                 if (0 <= weight(q))
 334                                         break;
 335                         }
 336                         if (!q)
 337                                 continue;
 338
 339                         /*
 340                          * weight for p is unknown but q is known.
 341                          * add one for p itself if p is to be counted,
 342                          * otherwise inherit it from q directly.
 343                          */
 344                         if (!(flags & TREESAME)) {
 345                                 weight_set(p, weight(q)+1);
 346                                 counted++;
 347                                 show_list("bisection 2 count one",
 348                                           counted, nr, list);
 349                         }
 350                         else
 351                                 weight_set(p, weight(q));
 352
 353                         /* Does it happen to be at exactly half-way? */
 354                         if (!find_all && halfway(p, nr))
 355                                 return p;
 356                 }
 357         }
 358
 359         show_list("bisection 2 counted all", counted, nr, list);
 360
 361         if (!find_all)
 362                 return best_bisection(list, nr);
 363         else
 364                 return best_bisection_sorted(list, nr);
 365 }
 366
 367 void find_bisection(struct commit_list **commit_list, int *reaches,
 368                     int *all, int find_all)
 369 {
 370         int nr, on_list;
 371         struct commit_list *list, *p, *best, *next, *last;
 372         int *weights;
 373
 374         show_list("bisection 2 entry", 0, 0, *commit_list);
 375
 376         /*
 377          * Count the number of total and tree-changing items on the
 378          * list, while reversing the list.
 379          */
 380         for (nr = on_list = 0, last = NULL, p = *commit_list;
 381              p;
 382              p = next) {
 383                 unsigned flags = p->item->object.flags;
 384
 385                 next = p->next;
 386                 if (flags & UNINTERESTING) {
 387                         free(p);
 388                         continue;
 389                 }
 390                 p->next = last;
 391                 last = p;
 392                 if (!(flags & TREESAME))
 393                         nr++;
 394                 on_list++;
 395         }
 396         list = last;
 397         show_list("bisection 2 sorted", 0, nr, list);
 398
 399         *all = nr;
 400         weights = xcalloc(on_list, sizeof(*weights));
 401
 402         /* Do the real work of finding bisection commit. */
 403         best = do_find_bisection(list, nr, weights, find_all);
 404         if (best) {
 405                 if (!find_all) {
 406                         list->item = best->item;
 407                         free_commit_list(list->next);
 408                         best = list;
 409                         best->next = NULL;
 410                 }
 411                 *reaches = weight(best);
 412         }
 413         free(weights);
 414         *commit_list = best;
 415 }
 416
 417 static int register_ref(const char *refname, const struct object_id *oid,
 418                         int flags, void *cb_data)
 419 {
 420         struct strbuf good_prefix = STRBUF_INIT;
 421         strbuf_addstr(&good_prefix, term_good);
 422         strbuf_addstr(&good_prefix, "-");
 423
 424         if (!strcmp(refname, term_bad)) {
 425                 current_bad_oid = xmalloc(sizeof(*current_bad_oid));
 426                 oidcpy(current_bad_oid, oid);
 427         } else if (starts_with(refname, good_prefix.buf)) {
 428                 oid_array_append(&good_revs, oid);
 429         } else if (starts_with(refname, "skip-")) {
 430                 oid_array_append(&skipped_revs, oid);
 431         }
 432
 433         strbuf_release(&good_prefix);
 434
 435         return 0;
 436 }
 437
 438 static int read_bisect_refs(void)
 439 {
 440         return for_each_ref_in("refs/bisect/", register_ref, NULL);
 441 }
 442
 443 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
 444 static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
 445 static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
 446 static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
 447 static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
 448 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
 449 static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
 450 static GIT_PATH_FUNC(git_path_head_name, "head-name")
 451
 452 static void read_bisect_paths(struct argv_array *array)
 453 {
 454         struct strbuf str = STRBUF_INIT;
 455         const char *filename = git_path_bisect_names();
 456         FILE *fp = xfopen(filename, "r");
 457
 458         while (strbuf_getline_lf(&str, fp) != EOF) {
 459                 strbuf_trim(&str);
 460                 if (sq_dequote_to_argv_array(str.buf, array))
 461                         die(_("Badly quoted content in file '%s': %s"),
 462                             filename, str.buf);
 463         }
 464
 465         strbuf_release(&str);
 466         fclose(fp);
 467 }
 468
 469 static char *join_sha1_array_hex(struct oid_array *array, char delim)
 470 {
 471         struct strbuf joined_hexs = STRBUF_INIT;
 472         int i;
 473
 474         for (i = 0; i < array->nr; i++) {
 475                 strbuf_addstr(&joined_hexs, oid_to_hex(array->oid + i));
 476                 if (i + 1 < array->nr)
 477                         strbuf_addch(&joined_hexs, delim);
 478         }
 479
 480         return strbuf_detach(&joined_hexs, NULL);
 481 }
 482
 483 /*
 484  * In this function, passing a not NULL skipped_first is very special.
 485  * It means that we want to know if the first commit in the list is
 486  * skipped because we will want to test a commit away from it if it is
 487  * indeed skipped.
 488  * So if the first commit is skipped, we cannot take the shortcut to
 489  * just "return list" when we find the first non skipped commit, we
 490  * have to return a fully filtered list.
 491  *
 492  * We use (*skipped_first == -1) to mean "it has been found that the
 493  * first commit is not skipped". In this case *skipped_first is set back
 494  * to 0 just before the function returns.
 495  */
 496 struct commit_list *filter_skipped(struct commit_list *list,
 497                                    struct commit_list **tried,
 498                                    int show_all,
 499                                    int *count,
 500                                    int *skipped_first)
 501 {
 502         struct commit_list *filtered = NULL, **f = &filtered;
 503
 504         *tried = NULL;
 505
 506         if (skipped_first)
 507                 *skipped_first = 0;
 508         if (count)
 509                 *count = 0;
 510
 511         if (!skipped_revs.nr)
 512                 return list;
 513
 514         while (list) {
 515                 struct commit_list *next = list->next;
 516                 list->next = NULL;
 517                 if (0 <= oid_array_lookup(&skipped_revs, &list->item->object.oid)) {
 518                         if (skipped_first && !*skipped_first)
 519                                 *skipped_first = 1;
 520                         /* Move current to tried list */
 521                         *tried = list;
 522                         tried = &list->next;
 523                 } else {
 524                         if (!show_all) {
 525                                 if (!skipped_first || !*skipped_first)
 526                                         return list;
 527                         } else if (skipped_first && !*skipped_first) {
 528                                 /* This means we know it's not skipped */
 529                                 *skipped_first = -1;
 530                         }
 531                         /* Move current to filtered list */
 532                         *f = list;
 533                         f = &list->next;
 534                         if (count)
 535                                 (*count)++;
 536                 }
 537                 list = next;
 538         }
 539
 540         if (skipped_first && *skipped_first == -1)
 541                 *skipped_first = 0;
 542
 543         return filtered;
 544 }
 545
 546 #define PRN_MODULO 32768
 547
 548 /*
 549  * This is a pseudo random number generator based on "man 3 rand".
 550  * It is not used properly because the seed is the argument and it
 551  * is increased by one between each call, but that should not matter
 552  * for this application.
 553  */
 554 static unsigned get_prn(unsigned count) {
 555         count = count * 1103515245 + 12345;
 556         return (count/65536) % PRN_MODULO;
 557 }
 558
 559 /*
 560  * Custom integer square root from
 561  * https://en.wikipedia.org/wiki/Integer_square_root
 562  */
 563 static int sqrti(int val)
 564 {
 565         float d, x = val;
 566
 567         if (val == 0)
 568                 return 0;
 569
 570         do {
 571                 float y = (x + (float)val / x) / 2;
 572                 d = (y > x) ? y - x : x - y;
 573                 x = y;
 574         } while (d >= 0.5);
 575
 576         return (int)x;
 577 }
 578
 579 static struct commit_list *skip_away(struct commit_list *list, int count)
 580 {
 581         struct commit_list *cur, *previous;
 582         int prn, index, i;
 583
 584         prn = get_prn(count);
 585         index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);
 586
 587         cur = list;
 588         previous = NULL;
 589
 590         for (i = 0; cur; cur = cur->next, i++) {
 591                 if (i == index) {
 592                         if (oidcmp(&cur->item->object.oid, current_bad_oid))
 593                                 return cur;
 594                         if (previous)
 595                                 return previous;
 596                         return list;
 597                 }
 598                 previous = cur;
 599         }
 600
 601         return list;
 602 }
 603
 604 static struct commit_list *managed_skipped(struct commit_list *list,
 605                                            struct commit_list **tried)
 606 {
 607         int count, skipped_first;
 608
 609         *tried = NULL;
 610
 611         if (!skipped_revs.nr)
 612                 return list;
 613
 614         list = filter_skipped(list, tried, 0, &count, &skipped_first);
 615
 616         if (!skipped_first)
 617                 return list;
 618
 619         return skip_away(list, count);
 620 }
 621
 622 static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
 623                              const char *bad_format, const char *good_format,
 624                              int read_paths)
 625 {
 626         struct argv_array rev_argv = ARGV_ARRAY_INIT;
 627         int i;
 628
 629         init_revisions(revs, prefix);
 630         revs->abbrev = 0;
 631         revs->commit_format = CMIT_FMT_UNSPECIFIED;
 632
 633         /* rev_argv.argv[0] will be ignored by setup_revisions */
 634         argv_array_push(&rev_argv, "bisect_rev_setup");
 635         argv_array_pushf(&rev_argv, bad_format, oid_to_hex(current_bad_oid));
 636         for (i = 0; i < good_revs.nr; i++)
 637                 argv_array_pushf(&rev_argv, good_format,
 638                                  oid_to_hex(good_revs.oid + i));
 639         argv_array_push(&rev_argv, "--");
 640         if (read_paths)
 641                 read_bisect_paths(&rev_argv);
 642
 643         setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
 644         /* XXX leak rev_argv, as "revs" may still be pointing to it */
 645 }
 646
 647 static void bisect_common(struct rev_info *revs)
 648 {
 649         if (prepare_revision_walk(revs))
 650                 die("revision walk setup failed");
 651         if (revs->tree_objects)
 652                 mark_edges_uninteresting(revs, NULL);
 653 }
 654
 655 static void exit_if_skipped_commits(struct commit_list *tried,
 656                                     const struct object_id *bad)
 657 {
 658         if (!tried)
 659                 return;
 660
 661         printf("There are only 'skip'ped commits left to test.\n"
 662                "The first %s commit could be any of:\n", term_bad);
 663
 664         for ( ; tried; tried = tried->next)
 665                 printf("%s\n", oid_to_hex(&tried->item->object.oid));
 666
 667         if (bad)
 668                 printf("%s\n", oid_to_hex(bad));
 669         printf(_("We cannot bisect more!\n"));
 670         exit(2);
 671 }
 672
 673 static int is_expected_rev(const struct object_id *oid)
 674 {
 675         const char *filename = git_path_bisect_expected_rev();
 676         struct stat st;
 677         struct strbuf str = STRBUF_INIT;
 678         FILE *fp;
 679         int res = 0;
 680
 681         if (stat(filename, &st) || !S_ISREG(st.st_mode))
 682                 return 0;
 683
 684         fp = fopen_or_warn(filename, "r");
 685         if (!fp)
 686                 return 0;
 687
 688         if (strbuf_getline_lf(&str, fp) != EOF)
 689                 res = !strcmp(str.buf, oid_to_hex(oid));
 690
 691         strbuf_release(&str);
 692         fclose(fp);
 693
 694         return res;
 695 }
 696
 697 static int bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
 698 {
 699         char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
 700
 701         memcpy(bisect_rev_hex, oid_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
 702         update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
 703
 704         argv_checkout[2] = bisect_rev_hex;
 705         if (no_checkout) {
 706                 update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0,
 707                            UPDATE_REFS_DIE_ON_ERR);
 708         } else {
 709                 int res;
 710                 res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
 711                 if (res)
 712                         exit(res);
 713         }
 714
 715         argv_show_branch[1] = bisect_rev_hex;
 716         return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
 717 }
 718
 719 static struct commit *get_commit_reference(const struct object_id *oid)
 720 {
 721         struct commit *r = lookup_commit_reference(oid);
 722         if (!r)
 723                 die(_("Not a valid commit name %s"), oid_to_hex(oid));
 724         return r;
 725 }
 726
 727 static struct commit **get_bad_and_good_commits(int *rev_nr)
 728 {
 729         struct commit **rev;
 730         int i, n = 0;
 731
 732         ALLOC_ARRAY(rev, 1 + good_revs.nr);
 733         rev[n++] = get_commit_reference(current_bad_oid);
 734         for (i = 0; i < good_revs.nr; i++)
 735                 rev[n++] = get_commit_reference(good_revs.oid + i);
 736         *rev_nr = n;
 737
 738         return rev;
 739 }
 740
 741 static void handle_bad_merge_base(void)
 742 {
 743         if (is_expected_rev(current_bad_oid)) {
 744                 char *bad_hex = oid_to_hex(current_bad_oid);
 745                 char *good_hex = join_sha1_array_hex(&good_revs, ' ');
 746                 if (!strcmp(term_bad, "bad") && !strcmp(term_good, "good")) {
 747                         fprintf(stderr, _("The merge base %s is bad.\n"
 748                                 "This means the bug has been fixed "
 749                                 "between %s and [%s].\n"),
 750                                 bad_hex, bad_hex, good_hex);
 751                 } else if (!strcmp(term_bad, "new") && !strcmp(term_good, "old")) {
 752                         fprintf(stderr, _("The merge base %s is new.\n"
 753                                 "The property has changed "
 754                                 "between %s and [%s].\n"),
 755                                 bad_hex, bad_hex, good_hex);
 756                 } else {
 757                         fprintf(stderr, _("The merge base %s is %s.\n"
 758                                 "This means the first '%s' commit is "
 759                                 "between %s and [%s].\n"),
 760                                 bad_hex, term_bad, term_good, bad_hex, good_hex);
 761                 }
 762                 exit(3);
 763         }
 764
 765         fprintf(stderr, _("Some %s revs are not ancestors of the %s rev.\n"
 766                 "git bisect cannot work properly in this case.\n"
 767                 "Maybe you mistook %s and %s revs?\n"),
 768                 term_good, term_bad, term_good, term_bad);
 769         exit(1);
 770 }
 771
 772 static void handle_skipped_merge_base(const struct object_id *mb)
 773 {
 774         char *mb_hex = oid_to_hex(mb);
 775         char *bad_hex = oid_to_hex(current_bad_oid);
 776         char *good_hex = join_sha1_array_hex(&good_revs, ' ');
 777
 778         warning(_("the merge base between %s and [%s] "
 779                 "must be skipped.\n"
 780                 "So we cannot be sure the first %s commit is "
 781                 "between %s and %s.\n"
 782                 "We continue anyway."),
 783                 bad_hex, good_hex, term_bad, mb_hex, bad_hex);
 784         free(good_hex);
 785 }
 786
 787 /*
 788  * "check_merge_bases" checks that merge bases are not "bad" (or "new").
 789  *
 790  * - If one is "bad" (or "new"), it means the user assumed something wrong
 791  * and we must exit with a non 0 error code.
 792  * - If one is "good" (or "old"), that's good, we have nothing to do.
 793  * - If one is "skipped", we can't know but we should warn.
 794  * - If we don't know, we should check it out and ask the user to test.
 795  */
 796 static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
 797 {
 798         struct commit_list *result;
 799
 800         result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1);
 801
 802         for (; result; result = result->next) {
 803                 const struct object_id *mb = &result->item->object.oid;
 804                 if (!oidcmp(mb, current_bad_oid)) {
 805                         handle_bad_merge_base();
 806                 } else if (0 <= oid_array_lookup(&good_revs, mb)) {
 807                         continue;
 808                 } else if (0 <= oid_array_lookup(&skipped_revs, mb)) {
 809                         handle_skipped_merge_base(mb);
 810                 } else {
 811                         printf(_("Bisecting: a merge base must be tested\n"));
 812                         exit(bisect_checkout(mb, no_checkout));
 813                 }
 814         }
 815
 816         free_commit_list(result);
 817 }
 818
 819 static int check_ancestors(int rev_nr, struct commit **rev, const char *prefix)
 820 {
 821         struct rev_info revs;
 822         int res;
 823
 824         bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
 825
 826         bisect_common(&revs);
 827         res = (revs.commits != NULL);
 828
 829         /* Clean up objects used, as they will be reused. */
 830         clear_commit_marks_many(rev_nr, rev, ALL_REV_FLAGS);
 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, rev_nr;
 848         struct commit **rev;
 849
 850         if (!current_bad_oid)
 851                 die(_("a %s revision is needed"), term_bad);
 852
 853         /* Check if file BISECT_ANCESTORS_OK exists. */
 854         if (!stat(filename, &st) && S_ISREG(st.st_mode))
 855                 goto done;
 856
 857         /* Bisecting with no good rev is ok. */
 858         if (good_revs.nr == 0)
 859                 goto done;
 860
 861         /* Check if all good revs are ancestor of the bad rev. */
 862         rev = get_bad_and_good_commits(&rev_nr);
 863         if (check_ancestors(rev_nr, rev, prefix))
 864                 check_merge_bases(rev_nr, rev, no_checkout);
 865         free(rev);
 866
 867         /* Create file BISECT_ANCESTORS_OK. */
 868         fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
 869         if (fd < 0)
 870                 warning_errno(_("could not create file '%s'"),
 871                               filename);
 872         else
 873                 close(fd);
 874  done:
 875         free(filename);
 876 }
 877
 878 /*
 879  * This does "git diff-tree --pretty COMMIT" without one fork+exec.
 880  */
 881 static void show_diff_tree(const char *prefix, struct commit *commit)
 882 {
 883         struct rev_info opt;
 884
 885         /* diff-tree init */
 886         init_revisions(&opt, prefix);
 887         git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
 888         opt.abbrev = 0;
 889         opt.diff = 1;
 890
 891         /* This is what "--pretty" does */
 892         opt.verbose_header = 1;
 893         opt.use_terminator = 0;
 894         opt.commit_format = CMIT_FMT_DEFAULT;
 895
 896         /* diff-tree init */
 897         if (!opt.diffopt.output_format)
 898                 opt.diffopt.output_format = DIFF_FORMAT_RAW;
 899
 900         setup_revisions(0, NULL, &opt, NULL);
 901         log_tree_commit(&opt, commit);
 902 }
 903
 904 /*
 905  * The terms used for this bisect session are stored in BISECT_TERMS.
 906  * We read them and store them to adapt the messages accordingly.
 907  * Default is bad/good.
 908  */
 909 void read_bisect_terms(const char **read_bad, const char **read_good)
 910 {
 911         struct strbuf str = STRBUF_INIT;
 912         const char *filename = git_path_bisect_terms();
 913         FILE *fp = fopen(filename, "r");
 914
 915         if (!fp) {
 916                 if (errno == ENOENT) {
 917                         *read_bad = "bad";
 918                         *read_good = "good";
 919                         return;
 920                 } else {
 921                         die_errno(_("could not read file '%s'"), filename);
 922                 }
 923         } else {
 924                 strbuf_getline_lf(&str, fp);
 925                 *read_bad = strbuf_detach(&str, NULL);
 926                 strbuf_getline_lf(&str, fp);
 927                 *read_good = strbuf_detach(&str, NULL);
 928         }
 929         strbuf_release(&str);
 930         fclose(fp);
 931 }
 932
 933 /*
 934  * We use the convention that exiting with an exit code 10 means that
 935  * the bisection process finished successfully.
 936  * In this case the calling shell script should exit 0.
 937  *
 938  * If no_checkout is non-zero, the bisection process does not
 939  * checkout the trial commit but instead simply updates BISECT_HEAD.
 940  */
 941 int bisect_next_all(const char *prefix, int no_checkout)
 942 {
 943         struct rev_info revs;
 944         struct commit_list *tried;
 945         int reaches = 0, all = 0, nr, steps;
 946         struct object_id *bisect_rev;
 947         char *steps_msg;
 948
 949         read_bisect_terms(&term_bad, &term_good);
 950         if (read_bisect_refs())
 951                 die(_("reading bisect refs failed"));
 952
 953         check_good_are_ancestors_of_bad(prefix, no_checkout);
 954
 955         bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
 956         revs.limited = 1;
 957
 958         bisect_common(&revs);
 959
 960         find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
 961         revs.commits = managed_skipped(revs.commits, &tried);
 962
 963         if (!revs.commits) {
 964                 /*
 965                  * We should exit here only if the "bad"
 966                  * commit is also a "skip" commit.
 967                  */
 968                 exit_if_skipped_commits(tried, NULL);
 969
 970                 printf(_("%s was both %s and %s\n"),
 971                        oid_to_hex(current_bad_oid),
 972                        term_good,
 973                        term_bad);
 974                 exit(1);
 975         }
 976
 977         if (!all) {
 978                 fprintf(stderr, _("No testable commit found.\n"
 979                         "Maybe you started with bad path parameters?\n"));
 980                 exit(4);
 981         }
 982
 983         bisect_rev = &revs.commits->item->object.oid;
 984
 985         if (!oidcmp(bisect_rev, current_bad_oid)) {
 986                 exit_if_skipped_commits(tried, current_bad_oid);
 987                 printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
 988                         term_bad);
 989                 show_diff_tree(prefix, revs.commits->item);
 990                 /* This means the bisection process succeeded. */
 991                 exit(10);
 992         }
 993
 994         nr = all - reaches - 1;
 995         steps = estimate_bisect_steps(all);
 996
 997         steps_msg = xstrfmt(Q_("(roughly %d step)", "(roughly %d steps)",
 998                   steps), steps);
 999         /*
1000          * TRANSLATORS: the last %s will be replaced with "(roughly %d
1001          * steps)" translation.
1002          */
1003         printf(Q_("Bisecting: %d revision left to test after this %s\n",
1004                   "Bisecting: %d revisions left to test after this %s\n",
1005                   nr), nr, steps_msg);
1006         free(steps_msg);
1007
1008         return bisect_checkout(bisect_rev, no_checkout);
1009 }
1010
1011 static inline int log2i(int n)
1012 {
1013         int log2 = 0;
1014
1015         for (; n > 1; n >>= 1)
1016                 log2++;
1017
1018         return log2;
1019 }
1020
1021 static inline int exp2i(int n)
1022 {
1023         return 1 << n;
1024 }
1025
1026 /*
1027  * Estimate the number of bisect steps left (after the current step)
1028  *
1029  * For any x between 0 included and 2^n excluded, the probability for
1030  * n - 1 steps left looks like:
1031  *
1032  * P(2^n + x) == (2^n - x) / (2^n + x)
1033  *
1034  * and P(2^n + x) < 0.5 means 2^n < 3x
1035  */
1036 int estimate_bisect_steps(int all)
1037 {
1038         int n, x, e;
1039
1040         if (all < 3)
1041                 return 0;
1042
1043         n = log2i(all);
1044         e = exp2i(n);
1045         x = all - e;
1046
1047         return (e < 3 * x) ? n : n - 1;
1048 }
1049
1050 static int mark_for_removal(const char *refname, const struct object_id *oid,
1051                             int flag, void *cb_data)
1052 {
1053         struct string_list *refs = cb_data;
1054         char *ref = xstrfmt("refs/bisect%s", refname);
1055         string_list_append(refs, ref);
1056         return 0;
1057 }
1058
1059 int bisect_clean_state(void)
1060 {
1061         int result = 0;
1062
1063         /* There may be some refs packed during bisection */
1064         struct string_list refs_for_removal = STRING_LIST_INIT_NODUP;
1065         for_each_ref_in("refs/bisect", mark_for_removal, (void *) &refs_for_removal);
1066         string_list_append(&refs_for_removal, xstrdup("BISECT_HEAD"));
1067         result = delete_refs("bisect: remove", &refs_for_removal, REF_NO_DEREF);
1068         refs_for_removal.strdup_strings = 1;
1069         string_list_clear(&refs_for_removal, 0);
1070         unlink_or_warn(git_path_bisect_expected_rev());
1071         unlink_or_warn(git_path_bisect_ancestors_ok());
1072         unlink_or_warn(git_path_bisect_log());
1073         unlink_or_warn(git_path_bisect_names());
1074         unlink_or_warn(git_path_bisect_run());
1075         unlink_or_warn(git_path_bisect_terms());
1076         /* Cleanup head-name if it got left by an old version of git-bisect */
1077         unlink_or_warn(git_path_head_name());
1078         /*
1079          * Cleanup BISECT_START last to support the --no-checkout option
1080          * introduced in the commit 4796e823a.
1081          */
1082         unlink_or_warn(git_path_bisect_start());
1083
1084         return result;
1085 }