/src/git/bisect.c

Source (jump to first uncovered line)
#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "config.h"
#include "commit.h"
#include "diff.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "revision.h"
#include "refs.h"
#include "list-objects.h"
#include "quote.h"
#include "run-command.h"
#include "log-tree.h"
#include "bisect.h"
#include "oid-array.h"
#include "strvec.h"
#include "commit-slab.h"
#include "commit-reach.h"
#include "object-name.h"
#include "object-store-ll.h"
#include "path.h"
#include "dir.h"

static struct oid_array good_revs;
static struct oid_array skipped_revs;

static struct object_id *current_bad_oid;

static const char *term_bad;
static const char *term_good;

/* Remember to update object flag allocation in object.h */
#define COUNTED   (1u<<16)

/*
 * This is a truly stupid algorithm, but it's only
 * used for bisection, and we just don't care enough.
 *
 * We care just barely enough to avoid recursing for
 * non-merge entries.
 */
static int count_distance(struct commit_list *entry)
{
  int nr = 0;

  while (entry) {
    struct commit *commit = entry->item;
    struct commit_list *p;

    if (commit->object.flags & (UNINTERESTING | COUNTED))
      break;
    if (!(commit->object.flags & TREESAME))
      nr++;
    commit->object.flags |= COUNTED;
    p = commit->parents;
    entry = p;
    if (p) {
      p = p->next;
      while (p) {
        nr += count_distance(p);
        p = p->next;
      }
    }
  }

  return nr;
}

static void clear_distance(struct commit_list *list)
{
  while (list) {
    struct commit *commit = list->item;
    commit->object.flags &= ~COUNTED;
    list = list->next;
  }
}

define_commit_slab(commit_weight, int *);
static struct commit_weight commit_weight;

#define DEBUG_BISECT 0

static inline int weight(struct commit_list *elem)
{
  return **commit_weight_at(&commit_weight, elem->item);
}

static inline void weight_set(struct commit_list *elem, int weight)
{
  **commit_weight_at(&commit_weight, elem->item) = weight;
}

static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
{
  struct commit_list *p;
  int count;

  for (count = 0, p = commit->parents; p; p = p->next) {
    if (!(p->item->object.flags & UNINTERESTING))
      count++;
    if (bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY)
      break;
  }
  return count;
}

static inline int approx_halfway(struct commit_list *p, int nr)
{
  int diff;

  /*
   * Don't short-cut something we are not going to return!
   */
  if (p->item->object.flags & TREESAME)
    return 0;
  if (DEBUG_BISECT)
    return 0;
  /*
   * For small number of commits 2 and 3 are halfway of 5, and
   * 3 is halfway of 6 but 2 and 4 are not.
   */
  diff = 2 * weight(p) - nr;
  switch (diff) {
  case -1: case 0: case 1:
    return 1;
  default:
    /*
     * For large number of commits we are not so strict, it's
     * good enough if it's within ~0.1% of the halfway point,
     * e.g. 5000 is exactly halfway of 10000, but we consider
     * the values [4996, 5004] as halfway as well.
     */
    if (abs(diff) < nr / 1024)
      return 1;
    return 0;
  }
}

static void show_list(const char *debug, int counted, int nr,
          struct commit_list *list)
{
  struct commit_list *p;

  if (!DEBUG_BISECT)
    return;

  fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);

  for (p = list; p; p = p->next) {
    struct commit_list *pp;
    struct commit *commit = p->item;
    unsigned commit_flags = commit->object.flags;
    enum object_type type;
    unsigned long size;
    char *buf = repo_read_object_file(the_repository,
              &commit->object.oid, &type,
              &size);
    const char *subject_start;
    int subject_len;

    if (!buf)
      die(_("unable to read %s"), oid_to_hex(&commit->object.oid));

    fprintf(stderr, "%c%c%c ",
      (commit_flags & TREESAME) ? ' ' : 'T',
      (commit_flags & UNINTERESTING) ? 'U' : ' ',
      (commit_flags & COUNTED) ? 'C' : ' ');
    if (*commit_weight_at(&commit_weight, p->item))
      fprintf(stderr, "%3d", weight(p));
    else
      fprintf(stderr, "---");
    fprintf(stderr, " %.*s", 8, oid_to_hex(&commit->object.oid));
    for (pp = commit->parents; pp; pp = pp->next)
      fprintf(stderr, " %.*s", 8,
        oid_to_hex(&pp->item->object.oid));

    subject_len = find_commit_subject(buf, &subject_start);
    if (subject_len)
      fprintf(stderr, " %.*s", subject_len, subject_start);
    fprintf(stderr, "\n");
  }
}

static struct commit_list *best_bisection(struct commit_list *list, int nr)
{
  struct commit_list *p, *best;
  int best_distance = -1;

  best = list;
  for (p = list; p; p = p->next) {
    int distance;
    unsigned commit_flags = p->item->object.flags;

    if (commit_flags & TREESAME)
      continue;
    distance = weight(p);
    if (nr - distance < distance)
      distance = nr - distance;
    if (distance > best_distance) {
      best = p;
      best_distance = distance;
    }
  }

  return best;
}

struct commit_dist {
  struct commit *commit;
  int distance;
};

static int compare_commit_dist(const void *a_, const void *b_)
{
  struct commit_dist *a, *b;

  a = (struct commit_dist *)a_;
  b = (struct commit_dist *)b_;
  if (a->distance != b->distance)
    return b->distance - a->distance; /* desc sort */
  return oidcmp(&a->commit->object.oid, &b->commit->object.oid);
}

static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
{
  struct commit_list *p;
  struct commit_dist *array = xcalloc(nr, sizeof(*array));
  struct strbuf buf = STRBUF_INIT;
  int cnt, i;

  for (p = list, cnt = 0; p; p = p->next) {
    int distance;
    unsigned commit_flags = p->item->object.flags;

    if (commit_flags & TREESAME)
      continue;
    distance = weight(p);
    if (nr - distance < distance)
      distance = nr - distance;
    array[cnt].commit = p->item;
    array[cnt].distance = distance;
    cnt++;
  }
  QSORT(array, cnt, compare_commit_dist);
  for (p = list, i = 0; i < cnt; i++) {
    struct object *obj = &(array[i].commit->object);

    strbuf_reset(&buf);
    strbuf_addf(&buf, "dist=%d", array[i].distance);
    add_name_decoration(DECORATION_NONE, buf.buf, obj);

    p->item = array[i].commit;
    if (i < cnt - 1)
      p = p->next;
  }
  if (p) {
    free_commit_list(p->next);
    p->next = NULL;
  }
  strbuf_release(&buf);
  free(array);
  return list;
}

/*
 * zero or positive weight is the number of interesting commits it can
 * reach, including itself.  Especially, weight = 0 means it does not
 * reach any tree-changing commits (e.g. just above uninteresting one
 * but traversal is with pathspec).
 *
 * weight = -1 means it has one parent and its distance is yet to
 * be computed.
 *
 * weight = -2 means it has more than one parent and its distance is
 * unknown.  After running count_distance() first, they will get zero
 * or positive distance.
 */
static struct commit_list *do_find_bisection(struct commit_list *list,
               int nr, int *weights,
               unsigned bisect_flags)
{
  int n, counted;
  struct commit_list *p;

  counted = 0;

  for (n = 0, p = list; p; p = p->next) {
    struct commit *commit = p->item;
    unsigned commit_flags = commit->object.flags;

    *commit_weight_at(&commit_weight, p->item) = &weights[n++];
    switch (count_interesting_parents(commit, bisect_flags)) {
    case 0:
      if (!(commit_flags & TREESAME)) {
        weight_set(p, 1);
        counted++;
        show_list("bisection 2 count one",
            counted, nr, list);
      }
      /*
       * otherwise, it is known not to reach any
       * tree-changing commit and gets weight 0.
       */
      break;
    case 1:
      weight_set(p, -1);
      break;
    default:
      weight_set(p, -2);
      break;
    }
  }

  show_list("bisection 2 initialize", counted, nr, list);

  /*
   * If you have only one parent in the resulting set
   * then you can reach one commit more than that parent
   * can reach.  So we do not have to run the expensive
   * count_distance() for single strand of pearls.
   *
   * However, if you have more than one parents, you cannot
   * just add their distance and one for yourself, since
   * they usually reach the same ancestor and you would
   * end up counting them twice that way.
   *
   * So we will first count distance of merges the usual
   * way, and then fill the blanks using cheaper algorithm.
   */
  for (p = list; p; p = p->next) {
    if (p->item->object.flags & UNINTERESTING)
      continue;
    if (weight(p) != -2)
      continue;
    if (bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY)
      BUG("shouldn't be calling count-distance in fp mode");
    weight_set(p, count_distance(p));
    clear_distance(list);

    /* Does it happen to be at half-way? */
    if (!(bisect_flags & FIND_BISECTION_ALL) &&
          approx_halfway(p, nr))
      return p;
    counted++;
  }

  show_list("bisection 2 count_distance", counted, nr, list);

  while (counted < nr) {
    for (p = list; p; p = p->next) {
      struct commit_list *q;
      unsigned commit_flags = p->item->object.flags;

      if (0 <= weight(p))
        continue;

      for (q = p->item->parents;
           q;
           q = bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY ? NULL : q->next) {
        if (q->item->object.flags & UNINTERESTING)
          continue;
        if (0 <= weight(q))
          break;
      }
      if (!q)
        continue;

      /*
       * weight for p is unknown but q is known.
       * add one for p itself if p is to be counted,
       * otherwise inherit it from q directly.
       */
      if (!(commit_flags & TREESAME)) {
        weight_set(p, weight(q)+1);
        counted++;
        show_list("bisection 2 count one",
            counted, nr, list);
      }
      else
        weight_set(p, weight(q));

      /* Does it happen to be at half-way? */
      if (!(bisect_flags & FIND_BISECTION_ALL) &&
            approx_halfway(p, nr))
        return p;
    }
  }

  show_list("bisection 2 counted all", counted, nr, list);

  if (!(bisect_flags & FIND_BISECTION_ALL))
    return best_bisection(list, nr);
  else
    return best_bisection_sorted(list, nr);
}

void find_bisection(struct commit_list **commit_list, int *reaches,
        int *all, unsigned bisect_flags)
{
  int nr, on_list;
  struct commit_list *list, *p, *best, *next, *last;
  int *weights;

  show_list("bisection 2 entry", 0, 0, *commit_list);
  init_commit_weight(&commit_weight);

  /*
   * Count the number of total and tree-changing items on the
   * list, while reversing the list.
   */
  for (nr = on_list = 0, last = NULL, p = *commit_list;
       p;
       p = next) {
    unsigned commit_flags = p->item->object.flags;

    next = p->next;
    if (commit_flags & UNINTERESTING) {
      free(p);
      continue;
    }
    p->next = last;
    last = p;
    if (!(commit_flags & TREESAME))
      nr++;
    on_list++;
  }
  list = last;
  show_list("bisection 2 sorted", 0, nr, list);

  *all = nr;
  CALLOC_ARRAY(weights, on_list);

  /* Do the real work of finding bisection commit. */
  best = do_find_bisection(list, nr, weights, bisect_flags);
  if (best) {
    if (!(bisect_flags & FIND_BISECTION_ALL)) {
      list->item = best->item;
      free_commit_list(list->next);
      best = list;
      best->next = NULL;
    }
    *reaches = weight(best);
  }
  free(weights);
  *commit_list = best;
  clear_commit_weight(&commit_weight);
}

static int register_ref(const char *refname, const char *referent UNUSED, const struct object_id *oid,
      int flags UNUSED, void *cb_data UNUSED)
{
  struct strbuf good_prefix = STRBUF_INIT;
  strbuf_addstr(&good_prefix, term_good);
  strbuf_addstr(&good_prefix, "-");

  if (!strcmp(refname, term_bad)) {
    current_bad_oid = xmalloc(sizeof(*current_bad_oid));
    oidcpy(current_bad_oid, oid);
  } else if (starts_with(refname, good_prefix.buf)) {
    oid_array_append(&good_revs, oid);
  } else if (starts_with(refname, "skip-")) {
    oid_array_append(&skipped_revs, oid);
  }

  strbuf_release(&good_prefix);

  return 0;
}

static int read_bisect_refs(void)
{
  return refs_for_each_ref_in(get_main_ref_store(the_repository),
            "refs/bisect/", register_ref, NULL);
}

static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
static GIT_PATH_FUNC(git_path_bisect_ancestors_ok, "BISECT_ANCESTORS_OK")
static GIT_PATH_FUNC(git_path_bisect_run, "BISECT_RUN")
static GIT_PATH_FUNC(git_path_bisect_start, "BISECT_START")
static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
static GIT_PATH_FUNC(git_path_bisect_terms, "BISECT_TERMS")
static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")

static void read_bisect_paths(struct strvec *array)
{
  struct strbuf str = STRBUF_INIT;
  const char *filename = git_path_bisect_names();
  FILE *fp = xfopen(filename, "r");

  while (strbuf_getline_lf(&str, fp) != EOF) {
    strbuf_trim(&str);
    if (sq_dequote_to_strvec(str.buf, array))
      die(_("Badly quoted content in file '%s': %s"),
          filename, str.buf);
  }

  strbuf_release(&str);
  fclose(fp);
}

static char *join_oid_array_hex(struct oid_array *array, char delim)
{
  struct strbuf joined_hexs = STRBUF_INIT;
  int i;

  for (i = 0; i < array->nr; i++) {
    strbuf_addstr(&joined_hexs, oid_to_hex(array->oid + i));
    if (i + 1 < array->nr)
      strbuf_addch(&joined_hexs, delim);
  }

  return strbuf_detach(&joined_hexs, NULL);
}

/*
 * In this function, passing a not NULL skipped_first is very special.
 * It means that we want to know if the first commit in the list is
 * skipped because we will want to test a commit away from it if it is
 * indeed skipped.
 * So if the first commit is skipped, we cannot take the shortcut to
 * just "return list" when we find the first non skipped commit, we
 * have to return a fully filtered list.
 *
 * We use (*skipped_first == -1) to mean "it has been found that the
 * first commit is not skipped". In this case *skipped_first is set back
 * to 0 just before the function returns.
 */
struct commit_list *filter_skipped(struct commit_list *list,
           struct commit_list **tried,
           int show_all,
           int *count,
           int *skipped_first)
{
  struct commit_list *filtered = NULL, **f = &filtered;

  *tried = NULL;

  if (skipped_first)
    *skipped_first = 0;
  if (count)
    *count = 0;

  if (!skipped_revs.nr)
    return list;

  while (list) {
    struct commit_list *next = list->next;
    list->next = NULL;
    if (0 <= oid_array_lookup(&skipped_revs, &list->item->object.oid)) {
      if (skipped_first && !*skipped_first)
        *skipped_first = 1;
      /* Move current to tried list */
      *tried = list;
      tried = &list->next;
    } else {
      if (!show_all) {
        if (!skipped_first || !*skipped_first)
          return list;
      } else if (skipped_first && !*skipped_first) {
        /* This means we know it's not skipped */
        *skipped_first = -1;
      }
      /* Move current to filtered list */
      *f = list;
      f = &list->next;
      if (count)
        (*count)++;
    }
    list = next;
  }

  if (skipped_first && *skipped_first == -1)
    *skipped_first = 0;

  return filtered;
}

#define PRN_MODULO 32768

/*
 * This is a pseudo random number generator based on "man 3 rand".
 * It is not used properly because the seed is the argument and it
 * is increased by one between each call, but that should not matter
 * for this application.
 */
static unsigned get_prn(unsigned count)
{
  count = count * 1103515245 + 12345;
  return (count/65536) % PRN_MODULO;
}

/*
 * Custom integer square root from
 * https://en.wikipedia.org/wiki/Integer_square_root
 */
static int sqrti(int val)
{
  float d, x = val;

  if (!val)
    return 0;

  do {
    float y = (x + (float)val / x) / 2;
    d = (y > x) ? y - x : x - y;
    x = y;
  } while (d >= 0.5);

  return (int)x;
}

static struct commit_list *skip_away(struct commit_list *list, int count)
{
  struct commit_list *cur, *previous;
  int prn, index, i;

  prn = get_prn(count);
  index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);

  cur = list;
  previous = NULL;

  for (i = 0; cur; cur = cur->next, i++) {
    if (i == index) {
      if (!oideq(&cur->item->object.oid, current_bad_oid))
        return cur;
      if (previous)
        return previous;
      return list;
    }
    previous = cur;
  }

  return list;
}

static struct commit_list *managed_skipped(struct commit_list *list,
             struct commit_list **tried)
{
  int count, skipped_first;

  *tried = NULL;

  if (!skipped_revs.nr)
    return list;

  list = filter_skipped(list, tried, 0, &count, &skipped_first);

  if (!skipped_first)
    return list;

  return skip_away(list, count);
}

static void bisect_rev_setup(struct repository *r, struct rev_info *revs,
           struct strvec *rev_argv,
           const char *prefix,
           const char *bad_format, const char *good_format,
           int read_paths)
{
  struct setup_revision_opt opt = {
    .free_removed_argv_elements = 1,
  };
  int i;

  repo_init_revisions(r, revs, prefix);
  revs->abbrev = 0;
  revs->commit_format = CMIT_FMT_UNSPECIFIED;

  /* rev_argv.argv[0] will be ignored by setup_revisions */
  strvec_push(rev_argv, "bisect_rev_setup");
  strvec_pushf(rev_argv, bad_format, oid_to_hex(current_bad_oid));
  for (i = 0; i < good_revs.nr; i++)
    strvec_pushf(rev_argv, good_format,
           oid_to_hex(good_revs.oid + i));
  strvec_push(rev_argv, "--");
  if (read_paths)
    read_bisect_paths(rev_argv);

  setup_revisions(rev_argv->nr, rev_argv->v, revs, &opt);
}

static void bisect_common(struct rev_info *revs)
{
  if (prepare_revision_walk(revs))
    die("revision walk setup failed");
  if (revs->tree_objects)
    mark_edges_uninteresting(revs, NULL, 0);
}

static enum bisect_error error_if_skipped_commits(struct commit_list *tried,
            const struct object_id *bad)
{
  if (!tried)
    return BISECT_OK;

  printf("There are only 'skip'ped commits left to test.\n"
         "The first %s commit could be any of:\n", term_bad);

  for ( ; tried; tried = tried->next)
    printf("%s\n", oid_to_hex(&tried->item->object.oid));

  if (bad)
    printf("%s\n", oid_to_hex(bad));
  printf(_("We cannot bisect more!\n"));

  return BISECT_ONLY_SKIPPED_LEFT;
}

static int is_expected_rev(const struct object_id *oid)
{
  struct object_id expected_oid;
  if (refs_read_ref(get_main_ref_store(the_repository), "BISECT_EXPECTED_REV", &expected_oid))
    return 0;
  return oideq(oid, &expected_oid);
}

enum bisect_error bisect_checkout(const struct object_id *bisect_rev,
          int no_checkout)
{
  struct commit *commit;
  struct pretty_print_context pp = {0};
  struct strbuf commit_msg = STRBUF_INIT;

  refs_update_ref(get_main_ref_store(the_repository), NULL,
      "BISECT_EXPECTED_REV", bisect_rev, NULL, 0,
      UPDATE_REFS_DIE_ON_ERR);

  if (no_checkout) {
    refs_update_ref(get_main_ref_store(the_repository), NULL,
        "BISECT_HEAD", bisect_rev, NULL, 0,
        UPDATE_REFS_DIE_ON_ERR);
  } else {
    struct child_process cmd = CHILD_PROCESS_INIT;

    cmd.git_cmd = 1;
    strvec_pushl(&cmd.args, "checkout", "-q",
           oid_to_hex(bisect_rev), "--", NULL);
    if (run_command(&cmd))
      /*
       * Errors in `run_command()` itself, signaled by res < 0,
       * and errors in the child process, signaled by res > 0
       * can both be treated as regular BISECT_FAILED (-1).
       */
      return BISECT_FAILED;
  }

  commit = lookup_commit_reference(the_repository, bisect_rev);
  repo_format_commit_message(the_repository, commit, "[%H] %s%n",
           &commit_msg, &pp);
  fputs(commit_msg.buf, stdout);
  strbuf_release(&commit_msg);

  return BISECT_OK;
}

static struct commit *get_commit_reference(struct repository *r,
             const struct object_id *oid)
{
  struct commit *c = lookup_commit_reference(r, oid);
  if (!c)
    die(_("Not a valid commit name %s"), oid_to_hex(oid));
  return c;
}

static struct commit **get_bad_and_good_commits(struct repository *r,
            int *rev_nr)
{
  struct commit **rev;
  int i, n = 0;

  ALLOC_ARRAY(rev, 1 + good_revs.nr);
  rev[n++] = get_commit_reference(r, current_bad_oid);
  for (i = 0; i < good_revs.nr; i++)
    rev[n++] = get_commit_reference(r, good_revs.oid + i);
  *rev_nr = n;

  return rev;
}

static enum bisect_error handle_bad_merge_base(void)
{
  if (is_expected_rev(current_bad_oid)) {
    char *bad_hex = oid_to_hex(current_bad_oid);
    char *good_hex = join_oid_array_hex(&good_revs, ' ');
    if (!strcmp(term_bad, "bad") && !strcmp(term_good, "good")) {
      fprintf(stderr, _("The merge base %s is bad.\n"
        "This means the bug has been fixed "
        "between %s and [%s].\n"),
        bad_hex, bad_hex, good_hex);
    } else if (!strcmp(term_bad, "new") && !strcmp(term_good, "old")) {
      fprintf(stderr, _("The merge base %s is new.\n"
        "The property has changed "
        "between %s and [%s].\n"),
        bad_hex, bad_hex, good_hex);
    } else {
      fprintf(stderr, _("The merge base %s is %s.\n"
        "This means the first '%s' commit is "
        "between %s and [%s].\n"),
        bad_hex, term_bad, term_good, bad_hex, good_hex);
    }
    return BISECT_MERGE_BASE_CHECK;
  }

  fprintf(stderr, _("Some %s revs are not ancestors of the %s rev.\n"
    "git bisect cannot work properly in this case.\n"
    "Maybe you mistook %s and %s revs?\n"),
    term_good, term_bad, term_good, term_bad);
  return BISECT_FAILED;
}

static void handle_skipped_merge_base(const struct object_id *mb)
{
  char *mb_hex = oid_to_hex(mb);
  char *bad_hex = oid_to_hex(current_bad_oid);
  char *good_hex = join_oid_array_hex(&good_revs, ' ');

  warning(_("the merge base between %s and [%s] "
    "must be skipped.\n"
    "So we cannot be sure the first %s commit is "
    "between %s and %s.\n"
    "We continue anyway."),
    bad_hex, good_hex, term_bad, mb_hex, bad_hex);
  free(good_hex);
}

/*
 * "check_merge_bases" checks that merge bases are not "bad" (or "new").
 *
 * - If one is "bad" (or "new"), it means the user assumed something wrong
 * and we must return error with a non 0 error code.
 * - If one is "good" (or "old"), that's good, we have nothing to do.
 * - If one is "skipped", we can't know but we should warn.
 * - If we don't know, we should check it out and ask the user to test.
 * - If a merge base must be tested, on success return
 * BISECT_INTERNAL_SUCCESS_MERGE_BASE (-11) a special condition
 * for early success, this will be converted back to 0 in
 * check_good_are_ancestors_of_bad().
 */
static enum bisect_error check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
{
  enum bisect_error res = BISECT_OK;
  struct commit_list *result = NULL;

  if (repo_get_merge_bases_many(the_repository, rev[0], rev_nr - 1,
              rev + 1, &result) < 0)
    exit(128);

  for (; result; result = result->next) {
    const struct object_id *mb = &result->item->object.oid;
    if (oideq(mb, current_bad_oid)) {
      res = handle_bad_merge_base();
      break;
    } else if (0 <= oid_array_lookup(&good_revs, mb)) {
      continue;
    } else if (0 <= oid_array_lookup(&skipped_revs, mb)) {
      handle_skipped_merge_base(mb);
    } else {
      printf(_("Bisecting: a merge base must be tested\n"));
      res = bisect_checkout(mb, no_checkout);
      if (!res)
        /* indicate early success */
        res = BISECT_INTERNAL_SUCCESS_MERGE_BASE;
      break;
    }
  }

  free_commit_list(result);
  return res;
}

static int check_ancestors(struct repository *r, int rev_nr,
         struct commit **rev, const char *prefix)
{
  struct strvec rev_argv = STRVEC_INIT;
  struct rev_info revs;
  int res;

  bisect_rev_setup(r, &revs, &rev_argv, prefix, "^%s", "%s", 0);

  bisect_common(&revs);
  res = (revs.commits != NULL);

  /* Clean up objects used, as they will be reused. */
  clear_commit_marks_many(rev_nr, rev, ALL_REV_FLAGS);

  release_revisions(&revs);
  strvec_clear(&rev_argv);
  return res;
}

/*
 * "check_good_are_ancestors_of_bad" checks that all "good" revs are
 * ancestor of the "bad" rev.
 *
 * If that's not the case, we need to check the merge bases.
 * If a merge base must be tested by the user, its source code will be
 * checked out to be tested by the user and we will return.
 */

static enum bisect_error check_good_are_ancestors_of_bad(struct repository *r,
              const char *prefix,
              int no_checkout)
{
  char *filename;
  struct stat st;
  int fd, rev_nr;
  enum bisect_error res = BISECT_OK;
  struct commit **rev;

  if (!current_bad_oid)
    return error(_("a %s revision is needed"), term_bad);

  filename = git_pathdup("BISECT_ANCESTORS_OK");

  /* Check if file BISECT_ANCESTORS_OK exists. */
  if (!stat(filename, &st) && S_ISREG(st.st_mode))
    goto done;

  /* Bisecting with no good rev is ok. */
  if (!good_revs.nr)
    goto done;

  /* Check if all good revs are ancestor of the bad rev. */

  rev = get_bad_and_good_commits(r, &rev_nr);
  if (check_ancestors(r, rev_nr, rev, prefix))
    res = check_merge_bases(rev_nr, rev, no_checkout);
  free(rev);

  if (!res) {
    /* Create file BISECT_ANCESTORS_OK. */
    fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
    if (fd < 0)
      /*
       * BISECT_ANCESTORS_OK file is not absolutely necessary,
       * the bisection process will continue at the next
       * bisection step.
       * So, just signal with a warning that something
       * might be wrong.
       */
      warning_errno(_("could not create file '%s'"),
        filename);
    else
      close(fd);
  }
 done:
  free(filename);
  return res;
}

/*
 * Display a commit summary to the user.
 */
static void show_commit(struct commit *commit)
{
  struct child_process show = CHILD_PROCESS_INIT;

  /*
   * Call git show with --no-pager, as it would otherwise
   * paginate the "git show" output only, not the output
   * from bisect_next_all(); this can be fixed by moving
   * it into a --format parameter, but that would override
   * the user's default options for "git show", which we
   * are trying to honour.
   */
  strvec_pushl(&show.args,
         "--no-pager",
         "show",
         "--stat",
         "--summary",
         "--no-abbrev-commit",
         "--diff-merges=first-parent",
         oid_to_hex(&commit->object.oid), NULL);
  show.git_cmd = 1;
  if (run_command(&show))
    die(_("unable to start 'show' for object '%s'"),
        oid_to_hex(&commit->object.oid));
}

/*
 * The terms used for this bisect session are stored in BISECT_TERMS.
 * We read them and store them to adapt the messages accordingly.
 * Default is bad/good.
 */
void read_bisect_terms(const char **read_bad, const char **read_good)
{
  struct strbuf str = STRBUF_INIT;
  const char *filename = git_path_bisect_terms();
  FILE *fp = fopen(filename, "r");

  if (!fp) {
    if (errno == ENOENT) {
      *read_bad = "bad";
      *read_good = "good";
      return;
    } else {
      die_errno(_("could not read file '%s'"), filename);
    }
  } else {
    strbuf_getline_lf(&str, fp);
    *read_bad = strbuf_detach(&str, NULL);
    strbuf_getline_lf(&str, fp);
    *read_good = strbuf_detach(&str, NULL);
  }
  strbuf_release(&str);
  fclose(fp);
}

/*
 * We use the convention that return BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND (-10) means
 * the bisection process finished successfully.
 * In this case the calling function or command should not turn a
 * BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND return code into an error or a non zero exit code.
 *
 * Checking BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND
 * in bisect_helper::bisect_next() and only transforming it to 0 at
 * the end of bisect_helper::cmd_bisect__helper() helps bypassing
 * all the code related to finding a commit to test.
 */
enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
{
  struct strvec rev_argv = STRVEC_INIT;
  struct rev_info revs = REV_INFO_INIT;
  struct commit_list *tried;
  int reaches = 0, all = 0, nr, steps;
  enum bisect_error res = BISECT_OK;
  struct object_id *bisect_rev;
  char *steps_msg;
  /*
   * If no_checkout is non-zero, the bisection process does not
   * checkout the trial commit but instead simply updates BISECT_HEAD.
   */
  int no_checkout = refs_ref_exists(get_main_ref_store(the_repository),
            "BISECT_HEAD");
  unsigned bisect_flags = 0;

  read_bisect_terms(&term_bad, &term_good);
  if (read_bisect_refs())
    die(_("reading bisect refs failed"));

  if (file_exists(git_path_bisect_first_parent()))
    bisect_flags |= FIND_BISECTION_FIRST_PARENT_ONLY;

  if (skipped_revs.nr)
    bisect_flags |= FIND_BISECTION_ALL;

  res = check_good_are_ancestors_of_bad(r, prefix, no_checkout);
  if (res)
    goto cleanup;

  bisect_rev_setup(r, &revs, &rev_argv, prefix, "%s", "^%s", 1);

  revs.first_parent_only = !!(bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY);
  revs.limited = 1;

  bisect_common(&revs);

  find_bisection(&revs.commits, &reaches, &all, bisect_flags);
  revs.commits = managed_skipped(revs.commits, &tried);

  if (!revs.commits) {
    /*
     * We should return error here only if the "bad"
     * commit is also a "skip" commit.
     */
    res = error_if_skipped_commits(tried, NULL);
    if (res < 0)
      goto cleanup;
    printf(_("%s was both %s and %s\n"),
           oid_to_hex(current_bad_oid),
           term_good,
           term_bad);

    res = BISECT_FAILED;
    goto cleanup;
  }

  if (!all) {
    fprintf(stderr, _("No testable commit found.\n"
      "Maybe you started with bad path arguments?\n"));

    res = BISECT_NO_TESTABLE_COMMIT;
    goto cleanup;
  }

  bisect_rev = &revs.commits->item->object.oid;

  if (oideq(bisect_rev, current_bad_oid)) {
    res = error_if_skipped_commits(tried, current_bad_oid);
    if (res)
      return res;
    printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
      term_bad);

    show_commit(revs.commits->item);
    /*
     * This means the bisection process succeeded.
     * Using BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND (-10)
     * so that the call chain can simply check
     * for negative return values for early returns up
     * until the cmd_bisect__helper() caller.
     */
    res = BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND;
    goto cleanup;
  }

  nr = all - reaches - 1;
  steps = estimate_bisect_steps(all);

  steps_msg = xstrfmt(Q_("(roughly %d step)", "(roughly %d steps)",
      steps), steps);
  /*
   * TRANSLATORS: the last %s will be replaced with "(roughly %d
   * steps)" translation.
   */
  printf(Q_("Bisecting: %d revision left to test after this %s\n",
      "Bisecting: %d revisions left to test after this %s\n",
      nr), nr, steps_msg);
  free(steps_msg);
  /* Clean up objects used, as they will be reused. */
  repo_clear_commit_marks(r, ALL_REV_FLAGS);

  res = bisect_checkout(bisect_rev, no_checkout);
cleanup:
  release_revisions(&revs);
  strvec_clear(&rev_argv);
  return res;
}

static inline int exp2i(int n)
{
  return 1 << n;
}

/*
 * Estimate the number of bisect steps left (after the current step)
 *
 * For any x between 0 included and 2^n excluded, the probability for
 * n - 1 steps left looks like:
 *
 * P(2^n + x) == (2^n - x) / (2^n + x)
 *
 * and P(2^n + x) < 0.5 means 2^n < 3x
 */
int estimate_bisect_steps(int all)
{
  int n, x, e;

  if (all < 3)
    return 0;

  n = log2u(all);
  e = exp2i(n);
  x = all - e;

  return (e < 3 * x) ? n : n - 1;
}

static int mark_for_removal(const char *refname,
          const char *referent UNUSED,
          const struct object_id *oid UNUSED,
          int flag UNUSED, void *cb_data)
{
  struct string_list *refs = cb_data;
  char *ref = xstrfmt("refs/bisect%s", refname);
  string_list_append(refs, ref);
  return 0;
}

int bisect_clean_state(void)
{
  int result = 0;

  /* There may be some refs packed during bisection */
  struct string_list refs_for_removal = STRING_LIST_INIT_NODUP;
  refs_for_each_ref_in(get_main_ref_store(the_repository),
           "refs/bisect", mark_for_removal,
           (void *) &refs_for_removal);
  string_list_append(&refs_for_removal, xstrdup("BISECT_HEAD"));
  string_list_append(&refs_for_removal, xstrdup("BISECT_EXPECTED_REV"));
  result = refs_delete_refs(get_main_ref_store(the_repository),
          "bisect: remove", &refs_for_removal,
          REF_NO_DEREF);
  refs_for_removal.strdup_strings = 1;
  string_list_clear(&refs_for_removal, 0);
  unlink_or_warn(git_path_bisect_ancestors_ok());
  unlink_or_warn(git_path_bisect_log());
  unlink_or_warn(git_path_bisect_names());
  unlink_or_warn(git_path_bisect_run());
  unlink_or_warn(git_path_bisect_terms());
  unlink_or_warn(git_path_bisect_first_parent());
  /*
   * Cleanup BISECT_START last to support the --no-checkout option
   * introduced in the commit 4796e823a.
   */
  unlink_or_warn(git_path_bisect_start());

  return result;
}

Coverage Report

Created: 2024-09-16 06:10