Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 1092 insertions, 0 deletions

diff --git a/bisect.c b/bisect.c
new file mode 100644
index 000000000000..e87ac29a51be
--- /dev/null
+++ b/bisect.c
@@ -0,0 +1,1092 @@
+#include "cache.h"
+#include "config.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"
+#include "sha1-array.h"
+#include "argv-array.h"
+#include "commit-slab.h"
+#include "commit-reach.h"
+#include "object-store.h"
+
+static struct oid_array good_revs;
+static struct oid_array skipped_revs;
+
+static struct object_id *current_bad_oid;
+
+static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
+static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
+
+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)
+{
+	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;
+	}
+}
+
+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 flags = commit->object.flags;
+		enum object_type type;
+		unsigned long size;
+		char *buf = read_object_file(&commit->object.oid, &type,
+					     &size);
+		const char *subject_start;
+		int subject_len;
+
+		fprintf(stderr, "%c%c%c ",
+			(flags & TREESAME) ? ' ' : 'T',
+			(flags & UNINTERESTING) ? 'U' : ' ',
+			(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 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 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 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, 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,
+					     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;
+
+		*commit_weight_at(&commit_weight, p->item) = &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);
+}
+
+void find_bisection(struct commit_list **commit_list, int *reaches,
+		    int *all, int find_all)
+{
+	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 flags = p->item->object.flags;
+
+		next = p->next;
+		if (flags & UNINTERESTING) {
+			free(p);
+			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) {
+			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 struct object_id *oid,
+			int flags, void *cb_data)
+{
+	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 for_each_ref_in("refs/bisect/", register_ref, NULL);
+}
+
+static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_expected_rev, "BISECT_EXPECTED_REV")
+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_head_name, "head-name")
+
+static void read_bisect_paths(struct argv_array *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_argv_array(str.buf, array))
+			die(_("Badly quoted content in file '%s': %s"),
+			    filename, str.buf);
+	}
+
+	strbuf_release(&str);
+	fclose(fp);
+}
+
+static char *join_sha1_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 == 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 (!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,
+			     const char *prefix,
+			     const char *bad_format, const char *good_format,
+			     int read_paths)
+{
+	struct argv_array rev_argv = ARGV_ARRAY_INIT;
+	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 */
+	argv_array_push(&rev_argv, "bisect_rev_setup");
+	argv_array_pushf(&rev_argv, bad_format, oid_to_hex(current_bad_oid));
+	for (i = 0; i < good_revs.nr; i++)
+		argv_array_pushf(&rev_argv, good_format,
+				 oid_to_hex(good_revs.oid + i));
+	argv_array_push(&rev_argv, "--");
+	if (read_paths)
+		read_bisect_paths(&rev_argv);
+
+	setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
+	/* XXX leak rev_argv, as "revs" may still be pointing to it */
+}
+
+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 void exit_if_skipped_commits(struct commit_list *tried,
+				    const struct object_id *bad)
+{
+	if (!tried)
+		return;
+
+	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"));
+	exit(2);
+}
+
+static int is_expected_rev(const struct object_id *oid)
+{
+	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_or_warn(filename, "r");
+	if (!fp)
+		return 0;
+
+	if (strbuf_getline_lf(&str, fp) != EOF)
+		res = !strcmp(str.buf, oid_to_hex(oid));
+
+	strbuf_release(&str);
+	fclose(fp);
+
+	return res;
+}
+
+static int bisect_checkout(const struct object_id *bisect_rev, int no_checkout)
+{
+	char bisect_rev_hex[GIT_MAX_HEXSZ + 1];
+
+	memcpy(bisect_rev_hex, oid_to_hex(bisect_rev), GIT_SHA1_HEXSZ + 1);
+	update_ref(NULL, "BISECT_EXPECTED_REV", bisect_rev, NULL, 0, UPDATE_REFS_DIE_ON_ERR);
+
+	argv_checkout[2] = bisect_rev_hex;
+	if (no_checkout) {
+		update_ref(NULL, "BISECT_HEAD", bisect_rev, NULL, 0,
+			   UPDATE_REFS_DIE_ON_ERR);
+	} else {
+		int res;
+		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(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 void 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_sha1_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);
+		}
+		exit(3);
+	}
+
+	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);
+	exit(1);
+}
+
+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_sha1_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 exit 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.
+ */
+static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
+{
+	struct commit_list *result;
+
+	result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1);
+
+	for (; result; result = result->next) {
+		const struct object_id *mb = &result->item->object.oid;
+		if (oideq(mb, current_bad_oid)) {
+			handle_bad_merge_base();
+		} 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"));
+			exit(bisect_checkout(mb, no_checkout));
+		}
+	}
+
+	free_commit_list(result);
+}
+
+static int check_ancestors(struct repository *r, int rev_nr,
+			   struct commit **rev, const char *prefix)
+{
+	struct rev_info revs;
+	int res;
+
+	bisect_rev_setup(r, &revs, 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);
+
+	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(struct repository *r,
+					    const char *prefix,
+					    int no_checkout)
+{
+	char *filename = git_pathdup("BISECT_ANCESTORS_OK");
+	struct stat st;
+	int fd, rev_nr;
+	struct commit **rev;
+
+	if (!current_bad_oid)
+		die(_("a %s revision is needed"), term_bad);
+
+	/* 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 == 0)
+		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))
+		check_merge_bases(rev_nr, rev, no_checkout);
+	free(rev);
+
+	/* Create file BISECT_ANCESTORS_OK. */
+	fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+	if (fd < 0)
+		warning_errno(_("could not create file '%s'"),
+			      filename);
+	else
+		close(fd);
+ done:
+	free(filename);
+}
+
+/*
+ * This does "git diff-tree --pretty COMMIT" without one fork+exec.
+ */
+static void show_diff_tree(struct repository *r,
+			   const char *prefix,
+			   struct commit *commit)
+{
+	const char *argv[] = {
+		"diff-tree", "--pretty", "--stat", "--summary", "--cc", NULL
+	};
+	struct rev_info opt;
+
+	git_config(git_diff_ui_config, NULL);
+	repo_init_revisions(r, &opt, prefix);
+
+	setup_revisions(ARRAY_SIZE(argv) - 1, argv, &opt, NULL);
+	log_tree_commit(&opt, commit);
+}
+
+/*
+ * 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 exiting with an exit code 10 means that
+ * the bisection process finished successfully.
+ * In this case the calling shell script should exit 0.
+ *
+ * If no_checkout is non-zero, the bisection process does not
+ * checkout the trial commit but instead simply updates BISECT_HEAD.
+ */
+int bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
+{
+	struct rev_info revs;
+	struct commit_list *tried;
+	int reaches = 0, all = 0, nr, steps;
+	struct object_id *bisect_rev;
+	char *steps_msg;
+
+	read_bisect_terms(&term_bad, &term_good);
+	if (read_bisect_refs())
+		die(_("reading bisect refs failed"));
+
+	check_good_are_ancestors_of_bad(r, prefix, no_checkout);
+
+	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
+	revs.limited = 1;
+
+	bisect_common(&revs);
+
+	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.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 %s and %s\n"),
+		       oid_to_hex(current_bad_oid),
+		       term_good,
+		       term_bad);
+		exit(1);
+	}
+
+	if (!all) {
+		fprintf(stderr, _("No testable commit found.\n"
+			"Maybe you started with bad path parameters?\n"));
+		exit(4);
+	}
+
+	bisect_rev = &revs.commits->item->object.oid;
+
+	if (oideq(bisect_rev, current_bad_oid)) {
+		exit_if_skipped_commits(tried, current_bad_oid);
+		printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
+			term_bad);
+		show_diff_tree(r, prefix, revs.commits->item);
+		/* This means the bisection process succeeded. */
+		exit(10);
+	}
+
+	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);
+
+	return bisect_checkout(bisect_rev, no_checkout);
+}
+
+static inline int log2i(int n)
+{
+	int log2 = 0;
+
+	for (; n > 1; n >>= 1)
+		log2++;
+
+	return log2;
+}
+
+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 = log2i(all);
+	e = exp2i(n);
+	x = all - e;
+
+	return (e < 3 * x) ? n : n - 1;
+}
+
+static int mark_for_removal(const char *refname, const struct object_id *oid,
+			    int flag, 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;
+	for_each_ref_in("refs/bisect", mark_for_removal, (void *) &refs_for_removal);
+	string_list_append(&refs_for_removal, xstrdup("BISECT_HEAD"));
+	result = delete_refs("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_expected_rev());
+	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());
+	/* Cleanup head-name if it got left by an old version of git-bisect */
+	unlink_or_warn(git_path_head_name());
+	/*
+	 * Cleanup BISECT_START last to support the --no-checkout option
+	 * introduced in the commit 4796e823a.
+	 */
+	unlink_or_warn(git_path_bisect_start());
+
+	return result;
+}