bisect.con commit Sync with 2.15.3 (424aac6)
   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
  16static struct oid_array good_revs;
  17static struct oid_array skipped_revs;
  18
  19static struct object_id *current_bad_oid;
  20
  21static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
  22static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
  23
  24static const char *term_bad;
  25static 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 */
  37static 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
  64static 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
  75static inline int weight(struct commit_list *elem)
  76{
  77        return *((int*)(elem->item->util));
  78}
  79
  80static inline void weight_set(struct commit_list *elem, int weight)
  81{
  82        *((int*)(elem->item->util)) = weight;
  83}
  84
  85static 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
  98static 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
 122static 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
 160static 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
 184struct commit_dist {
 185        struct commit *commit;
 186        int distance;
 187};
 188
 189static 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
 200static 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 */
 254static 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
 366void 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
 416static 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
 437static int read_bisect_refs(void)
 438{
 439        return for_each_ref_in("refs/bisect/", register_ref, NULL);
 440}
 441
 442static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
 443static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
 444static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
 445static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
 446static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
 447static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
 448static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
 449static GIT_PATH_FUNC(git_path_head_name, "head-name")
 450
 451static 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
 468static 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 */
 495struct 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 */
 553static 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 */
 562static 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
 578static 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
 603static 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
 621static 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
 646static 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
 654static 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
 672static 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
 696static 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
 718static 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
 726static 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
 740static 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
 771static 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 */
 795static 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
 818static 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 */
 842static 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 */
 880static 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 */
 908void 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 */
 940int 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
1010static 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
1020static 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 */
1035int 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
1049static 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
1058int 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}