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-rw-r--r--bisect.c1006
1 files changed, 1006 insertions, 0 deletions
diff --git a/bisect.c b/bisect.c
new file mode 100644
index 0000000000..dc18db8af9
--- /dev/null
+++ b/bisect.c
@@ -0,0 +1,1006 @@
+#include "cache.h"
+#include "commit.h"
+#include "diff.h"
+#include "revision.h"
+#include "refs.h"
+#include "list-objects.h"
+#include "quote.h"
+#include "sha1-lookup.h"
+#include "run-command.h"
+#include "log-tree.h"
+#include "bisect.h"
+
+struct sha1_array {
+ unsigned char (*sha1)[20];
+ int sha1_nr;
+ int sha1_alloc;
+ int sorted;
+};
+
+static struct sha1_array good_revs;
+static struct sha1_array skipped_revs;
+
+static const unsigned char *current_bad_sha1;
+
+struct argv_array {
+ const char **argv;
+ int argv_nr;
+ int argv_alloc;
+};
+
+static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
+static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
+
+/* bits #0-15 in revision.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 DEBUG_BISECT 0
+
+static inline int weight(struct commit_list *elem)
+{
+ return *((int*)(elem->item->util));
+}
+
+static inline void weight_set(struct commit_list *elem, int weight)
+{
+ *((int*)(elem->item->util)) = weight;
+}
+
+static int count_interesting_parents(struct commit *commit)
+{
+ struct commit_list *p;
+ int count;
+
+ for (count = 0, p = commit->parents; p; p = p->next) {
+ if (p->item->object.flags & UNINTERESTING)
+ continue;
+ count++;
+ }
+ return count;
+}
+
+static inline int halfway(struct commit_list *p, int nr)
+{
+ /*
+ * Don't short-cut something we are not going to return!
+ */
+ if (p->item->object.flags & TREESAME)
+ return 0;
+ if (DEBUG_BISECT)
+ return 0;
+ /*
+ * 2 and 3 are halfway of 5.
+ * 3 is halfway of 6 but 2 and 4 are not.
+ */
+ switch (2 * weight(p) - nr) {
+ case -1: case 0: case 1:
+ return 1;
+ default:
+ return 0;
+ }
+}
+
+#if !DEBUG_BISECT
+#define show_list(a,b,c,d) do { ; } while (0)
+#else
+static void show_list(const char *debug, int counted, int nr,
+ struct commit_list *list)
+{
+ struct commit_list *p;
+
+ 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 flags = commit->object.flags;
+ enum object_type type;
+ unsigned long size;
+ char *buf = read_sha1_file(commit->object.sha1, &type, &size);
+ char *ep, *sp;
+
+ fprintf(stderr, "%c%c%c ",
+ (flags & TREESAME) ? ' ' : 'T',
+ (flags & UNINTERESTING) ? 'U' : ' ',
+ (flags & COUNTED) ? 'C' : ' ');
+ if (commit->util)
+ fprintf(stderr, "%3d", weight(p));
+ else
+ fprintf(stderr, "---");
+ fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
+ for (pp = commit->parents; pp; pp = pp->next)
+ fprintf(stderr, " %.*s", 8,
+ sha1_to_hex(pp->item->object.sha1));
+
+ sp = strstr(buf, "\n\n");
+ if (sp) {
+ sp += 2;
+ for (ep = sp; *ep && *ep != '\n'; ep++)
+ ;
+ fprintf(stderr, " %.*s", (int)(ep - sp), sp);
+ }
+ fprintf(stderr, "\n");
+ }
+}
+#endif /* DEBUG_BISECT */
+
+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 flags = p->item->object.flags;
+
+ if (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 hashcmp(a->commit->object.sha1, b->commit->object.sha1);
+}
+
+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));
+ int cnt, i;
+
+ for (p = list, cnt = 0; p; p = p->next) {
+ int distance;
+ unsigned flags = p->item->object.flags;
+
+ if (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, sizeof(*array), compare_commit_dist);
+ for (p = list, i = 0; i < cnt; i++) {
+ struct name_decoration *r = xmalloc(sizeof(*r) + 100);
+ struct object *obj = &(array[i].commit->object);
+
+ sprintf(r->name, "dist=%d", array[i].distance);
+ r->next = add_decoration(&name_decoration, obj, r);
+ p->item = array[i].commit;
+ p = p->next;
+ }
+ if (p)
+ p->next = NULL;
+ 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,
+ int find_all)
+{
+ int n, counted;
+ struct commit_list *p;
+
+ counted = 0;
+
+ for (n = 0, p = list; p; p = p->next) {
+ struct commit *commit = p->item;
+ unsigned flags = commit->object.flags;
+
+ p->item->util = &weights[n++];
+ switch (count_interesting_parents(commit)) {
+ case 0:
+ if (!(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;
+ weight_set(p, count_distance(p));
+ clear_distance(list);
+
+ /* Does it happen to be at exactly half-way? */
+ if (!find_all && 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 flags = p->item->object.flags;
+
+ if (0 <= weight(p))
+ continue;
+ for (q = p->item->parents; q; q = 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 (!(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 exactly half-way? */
+ if (!find_all && halfway(p, nr))
+ return p;
+ }
+ }
+
+ show_list("bisection 2 counted all", counted, nr, list);
+
+ if (!find_all)
+ return best_bisection(list, nr);
+ else
+ return best_bisection_sorted(list, nr);
+}
+
+struct commit_list *find_bisection(struct commit_list *list,
+ int *reaches, int *all,
+ int find_all)
+{
+ int nr, on_list;
+ struct commit_list *p, *best, *next, *last;
+ int *weights;
+
+ show_list("bisection 2 entry", 0, 0, list);
+
+ /*
+ * Count the number of total and tree-changing items on the
+ * list, while reversing the list.
+ */
+ for (nr = on_list = 0, last = NULL, p = list;
+ p;
+ p = next) {
+ unsigned flags = p->item->object.flags;
+
+ next = p->next;
+ if (flags & UNINTERESTING)
+ continue;
+ p->next = last;
+ last = p;
+ if (!(flags & TREESAME))
+ nr++;
+ on_list++;
+ }
+ list = last;
+ show_list("bisection 2 sorted", 0, nr, list);
+
+ *all = nr;
+ weights = xcalloc(on_list, sizeof(*weights));
+
+ /* Do the real work of finding bisection commit. */
+ best = do_find_bisection(list, nr, weights, find_all);
+ if (best) {
+ if (!find_all)
+ best->next = NULL;
+ *reaches = weight(best);
+ }
+ free(weights);
+ return best;
+}
+
+static void argv_array_push(struct argv_array *array, const char *string)
+{
+ ALLOC_GROW(array->argv, array->argv_nr + 1, array->argv_alloc);
+ array->argv[array->argv_nr++] = string;
+}
+
+static void argv_array_push_sha1(struct argv_array *array,
+ const unsigned char *sha1,
+ const char *format)
+{
+ struct strbuf buf = STRBUF_INIT;
+ strbuf_addf(&buf, format, sha1_to_hex(sha1));
+ argv_array_push(array, strbuf_detach(&buf, NULL));
+}
+
+static void sha1_array_push(struct sha1_array *array,
+ const unsigned char *sha1)
+{
+ ALLOC_GROW(array->sha1, array->sha1_nr + 1, array->sha1_alloc);
+ hashcpy(array->sha1[array->sha1_nr++], sha1);
+}
+
+static int register_ref(const char *refname, const unsigned char *sha1,
+ int flags, void *cb_data)
+{
+ if (!strcmp(refname, "bad")) {
+ current_bad_sha1 = sha1;
+ } else if (!prefixcmp(refname, "good-")) {
+ sha1_array_push(&good_revs, sha1);
+ } else if (!prefixcmp(refname, "skip-")) {
+ sha1_array_push(&skipped_revs, sha1);
+ }
+
+ return 0;
+}
+
+static int read_bisect_refs(void)
+{
+ return for_each_ref_in("refs/bisect/", register_ref, NULL);
+}
+
+static void read_bisect_paths(struct argv_array *array)
+{
+ struct strbuf str = STRBUF_INIT;
+ const char *filename = git_path("BISECT_NAMES");
+ FILE *fp = fopen(filename, "r");
+
+ if (!fp)
+ die_errno("Could not open file '%s'", filename);
+
+ while (strbuf_getline(&str, fp, '\n') != EOF) {
+ char *quoted;
+ int res;
+
+ strbuf_trim(&str);
+ quoted = strbuf_detach(&str, NULL);
+ res = sq_dequote_to_argv(quoted, &array->argv,
+ &array->argv_nr, &array->argv_alloc);
+ if (res)
+ die("Badly quoted content in file '%s': %s",
+ filename, quoted);
+ }
+
+ strbuf_release(&str);
+ fclose(fp);
+}
+
+static int array_cmp(const void *a, const void *b)
+{
+ return hashcmp(a, b);
+}
+
+static void sort_sha1_array(struct sha1_array *array)
+{
+ qsort(array->sha1, array->sha1_nr, sizeof(*array->sha1), array_cmp);
+
+ array->sorted = 1;
+}
+
+static const unsigned char *sha1_access(size_t index, void *table)
+{
+ unsigned char (*array)[20] = table;
+ return array[index];
+}
+
+static int lookup_sha1_array(struct sha1_array *array,
+ const unsigned char *sha1)
+{
+ if (!array->sorted)
+ sort_sha1_array(array);
+
+ return sha1_pos(sha1, array->sha1, array->sha1_nr, sha1_access);
+}
+
+static char *join_sha1_array_hex(struct sha1_array *array, char delim)
+{
+ struct strbuf joined_hexs = STRBUF_INIT;
+ int i;
+
+ for (i = 0; i < array->sha1_nr; i++) {
+ strbuf_addstr(&joined_hexs, sha1_to_hex(array->sha1[i]));
+ if (i + 1 < array->sha1_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.sha1_nr)
+ return list;
+
+ while (list) {
+ struct commit_list *next = list->next;
+ list->next = NULL;
+ if (0 <= lookup_sha1_array(&skipped_revs,
+ list->item->object.sha1)) {
+ 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.
+ */
+int get_prn(int count) {
+ count = count * 1103515245 + 12345;
+ return ((unsigned)(count/65536) % PRN_MODULO);
+}
+
+/*
+ * Custom integer square root from
+ * http://en.wikipedia.org/wiki/Integer_square_root
+ */
+static int sqrti(int val)
+{
+ float d, x = val;
+
+ if (val == 0)
+ 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 (hashcmp(cur->item->object.sha1, current_bad_sha1))
+ 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.sha1_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 rev_info *revs, const char *prefix,
+ const char *bad_format, const char *good_format,
+ int read_paths)
+{
+ struct argv_array rev_argv = { NULL, 0, 0 };
+ int i;
+
+ init_revisions(revs, prefix);
+ revs->abbrev = 0;
+ revs->commit_format = CMIT_FMT_UNSPECIFIED;
+
+ /* rev_argv.argv[0] will be ignored by setup_revisions */
+ argv_array_push(&rev_argv, xstrdup("bisect_rev_setup"));
+ argv_array_push_sha1(&rev_argv, current_bad_sha1, bad_format);
+ for (i = 0; i < good_revs.sha1_nr; i++)
+ argv_array_push_sha1(&rev_argv, good_revs.sha1[i],
+ good_format);
+ argv_array_push(&rev_argv, xstrdup("--"));
+ if (read_paths)
+ read_bisect_paths(&rev_argv);
+ argv_array_push(&rev_argv, NULL);
+
+ setup_revisions(rev_argv.argv_nr, rev_argv.argv, revs, NULL);
+}
+
+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->commits, revs, NULL);
+}
+
+static void exit_if_skipped_commits(struct commit_list *tried,
+ const unsigned char *bad)
+{
+ if (!tried)
+ return;
+
+ printf("There are only 'skip'ped commits left to test.\n"
+ "The first bad commit could be any of:\n");
+ print_commit_list(tried, "%s\n", "%s\n");
+ if (bad)
+ printf("%s\n", sha1_to_hex(bad));
+ printf("We cannot bisect more!\n");
+ exit(2);
+}
+
+static int is_expected_rev(const unsigned char *sha1)
+{
+ const char *filename = git_path("BISECT_EXPECTED_REV");
+ struct stat st;
+ struct strbuf str = STRBUF_INIT;
+ FILE *fp;
+ int res = 0;
+
+ if (stat(filename, &st) || !S_ISREG(st.st_mode))
+ return 0;
+
+ fp = fopen(filename, "r");
+ if (!fp)
+ return 0;
+
+ if (strbuf_getline(&str, fp, '\n') != EOF)
+ res = !strcmp(str.buf, sha1_to_hex(sha1));
+
+ strbuf_release(&str);
+ fclose(fp);
+
+ return res;
+}
+
+static void mark_expected_rev(char *bisect_rev_hex)
+{
+ int len = strlen(bisect_rev_hex);
+ const char *filename = git_path("BISECT_EXPECTED_REV");
+ int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+
+ if (fd < 0)
+ die_errno("could not create file '%s'", filename);
+
+ bisect_rev_hex[len] = '\n';
+ write_or_die(fd, bisect_rev_hex, len + 1);
+ bisect_rev_hex[len] = '\0';
+
+ if (close(fd) < 0)
+ die("closing file %s: %s", filename, strerror(errno));
+}
+
+static int bisect_checkout(char *bisect_rev_hex)
+{
+ int res;
+
+ mark_expected_rev(bisect_rev_hex);
+
+ argv_checkout[2] = bisect_rev_hex;
+ res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
+ if (res)
+ exit(res);
+
+ argv_show_branch[1] = bisect_rev_hex;
+ return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
+}
+
+static struct commit *get_commit_reference(const unsigned char *sha1)
+{
+ struct commit *r = lookup_commit_reference(sha1);
+ if (!r)
+ die("Not a valid commit name %s", sha1_to_hex(sha1));
+ return r;
+}
+
+static struct commit **get_bad_and_good_commits(int *rev_nr)
+{
+ int len = 1 + good_revs.sha1_nr;
+ struct commit **rev = xmalloc(len * sizeof(*rev));
+ int i, n = 0;
+
+ rev[n++] = get_commit_reference(current_bad_sha1);
+ for (i = 0; i < good_revs.sha1_nr; i++)
+ rev[n++] = get_commit_reference(good_revs.sha1[i]);
+ *rev_nr = n;
+
+ return rev;
+}
+
+static void handle_bad_merge_base(void)
+{
+ if (is_expected_rev(current_bad_sha1)) {
+ char *bad_hex = sha1_to_hex(current_bad_sha1);
+ char *good_hex = join_sha1_array_hex(&good_revs, ' ');
+
+ 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);
+
+ exit(3);
+ }
+
+ fprintf(stderr, "Some good revs are not ancestor of the bad rev.\n"
+ "git bisect cannot work properly in this case.\n"
+ "Maybe you mistake good and bad revs?\n");
+ exit(1);
+}
+
+static void handle_skipped_merge_base(const unsigned char *mb)
+{
+ char *mb_hex = sha1_to_hex(mb);
+ char *bad_hex = sha1_to_hex(current_bad_sha1);
+ char *good_hex = join_sha1_array_hex(&good_revs, ' ');
+
+ fprintf(stderr, "Warning: the merge base between %s and [%s] "
+ "must be skipped.\n"
+ "So we cannot be sure the first bad commit is "
+ "between %s and %s.\n"
+ "We continue anyway.\n",
+ bad_hex, good_hex, mb_hex, bad_hex);
+ free(good_hex);
+}
+
+/*
+ * "check_merge_bases" checks that merge bases are not "bad".
+ *
+ * - If one is "bad", it means the user assumed something wrong
+ * and we must exit with a non 0 error code.
+ * - If one is "good", 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.
+ */
+static void check_merge_bases(void)
+{
+ struct commit_list *result;
+ int rev_nr;
+ struct commit **rev = get_bad_and_good_commits(&rev_nr);
+
+ result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 0);
+
+ for (; result; result = result->next) {
+ const unsigned char *mb = result->item->object.sha1;
+ if (!hashcmp(mb, current_bad_sha1)) {
+ handle_bad_merge_base();
+ } else if (0 <= lookup_sha1_array(&good_revs, mb)) {
+ continue;
+ } else if (0 <= lookup_sha1_array(&skipped_revs, mb)) {
+ handle_skipped_merge_base(mb);
+ } else {
+ printf("Bisecting: a merge base must be tested\n");
+ exit(bisect_checkout(sha1_to_hex(mb)));
+ }
+ }
+
+ free(rev);
+ free_commit_list(result);
+}
+
+static int check_ancestors(const char *prefix)
+{
+ struct rev_info revs;
+ struct object_array pending_copy;
+ int i, res;
+
+ bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
+
+ /* Save pending objects, so they can be cleaned up later. */
+ memset(&pending_copy, 0, sizeof(pending_copy));
+ for (i = 0; i < revs.pending.nr; i++)
+ add_object_array(revs.pending.objects[i].item,
+ revs.pending.objects[i].name,
+ &pending_copy);
+
+ bisect_common(&revs);
+ res = (revs.commits != NULL);
+
+ /* Clean up objects used, as they will be reused. */
+ for (i = 0; i < pending_copy.nr; i++) {
+ struct object *o = pending_copy.objects[i].item;
+ clear_commit_marks((struct commit *)o, ALL_REV_FLAGS);
+ }
+
+ 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 exit.
+ */
+static void check_good_are_ancestors_of_bad(const char *prefix)
+{
+ const char *filename = git_path("BISECT_ANCESTORS_OK");
+ struct stat st;
+ int fd;
+
+ if (!current_bad_sha1)
+ die("a bad revision is needed");
+
+ /* Check if file BISECT_ANCESTORS_OK exists. */
+ if (!stat(filename, &st) && S_ISREG(st.st_mode))
+ return;
+
+ /* Bisecting with no good rev is ok. */
+ if (good_revs.sha1_nr == 0)
+ return;
+
+ /* Check if all good revs are ancestor of the bad rev. */
+ if (check_ancestors(prefix))
+ check_merge_bases();
+
+ /* Create file BISECT_ANCESTORS_OK. */
+ fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+ if (fd < 0)
+ warning("could not create file '%s': %s",
+ filename, strerror(errno));
+ else
+ close(fd);
+}
+
+/*
+ * This does "git diff-tree --pretty COMMIT" without one fork+exec.
+ */
+static void show_diff_tree(const char *prefix, struct commit *commit)
+{
+ struct rev_info opt;
+
+ /* diff-tree init */
+ init_revisions(&opt, prefix);
+ git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
+ opt.abbrev = 0;
+ opt.diff = 1;
+
+ /* This is what "--pretty" does */
+ opt.verbose_header = 1;
+ opt.use_terminator = 0;
+ opt.commit_format = CMIT_FMT_DEFAULT;
+
+ /* diff-tree init */
+ if (!opt.diffopt.output_format)
+ opt.diffopt.output_format = DIFF_FORMAT_RAW;
+
+ log_tree_commit(&opt, commit);
+}
+
+/*
+ * We use the convention that exiting with an exit code 10 means that
+ * the bisection process finished successfully.
+ * In this case the calling shell script should exit 0.
+ */
+int bisect_next_all(const char *prefix)
+{
+ struct rev_info revs;
+ struct commit_list *tried;
+ int reaches = 0, all = 0, nr;
+ const unsigned char *bisect_rev;
+ char bisect_rev_hex[41];
+
+ if (read_bisect_refs())
+ die("reading bisect refs failed");
+
+ check_good_are_ancestors_of_bad(prefix);
+
+ bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
+ revs.limited = 1;
+
+ bisect_common(&revs);
+
+ revs.commits = find_bisection(revs.commits, &reaches, &all,
+ !!skipped_revs.sha1_nr);
+ revs.commits = managed_skipped(revs.commits, &tried);
+
+ if (!revs.commits) {
+ /*
+ * We should exit here only if the "bad"
+ * commit is also a "skip" commit.
+ */
+ exit_if_skipped_commits(tried, NULL);
+
+ printf("%s was both good and bad\n",
+ sha1_to_hex(current_bad_sha1));
+ exit(1);
+ }
+
+ bisect_rev = revs.commits->item->object.sha1;
+ memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), 41);
+
+ if (!hashcmp(bisect_rev, current_bad_sha1)) {
+ exit_if_skipped_commits(tried, current_bad_sha1);
+ printf("%s is the first bad commit\n", bisect_rev_hex);
+ show_diff_tree(prefix, revs.commits->item);
+ /* This means the bisection process succeeded. */
+ exit(10);
+ }
+
+ nr = all - reaches - 1;
+ printf("Bisecting: %d revisions left to test after this "
+ "(roughly %d steps)\n", nr, estimate_bisect_steps(all));
+
+ return bisect_checkout(bisect_rev_hex);
+}
+