bisect.c 23.6 KB
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#include "cache.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
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#include "refs.h"
#include "list-objects.h"
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#include "quote.h"
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#include "sha1-lookup.h"
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#include "run-command.h"
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#include "log-tree.h"
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#include "bisect.h"
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#include "sha1-array.h"
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#include "argv-array.h"
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static struct sha1_array good_revs;
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static struct sha1_array skipped_revs;
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static unsigned char *current_bad_sha1;
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static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
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static const char *argv_update_ref[] = {"update-ref", "--no-deref", "BISECT_HEAD", NULL, NULL};
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/* Remember to update object flag allocation in object.h */
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#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);
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		const char *subject_start;
		int subject_len;
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		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));

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

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static int register_ref(const char *refname, const unsigned char *sha1,
			int flags, void *cb_data)
{
	if (!strcmp(refname, "bad")) {
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		current_bad_sha1 = xmalloc(20);
		hashcpy(current_bad_sha1, sha1);
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	} else if (starts_with(refname, "good-")) {
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		sha1_array_append(&good_revs, sha1);
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	} else if (starts_with(refname, "skip-")) {
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		sha1_array_append(&skipped_revs, sha1);
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	}

	return 0;
}

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

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static void read_bisect_paths(struct argv_array *array)
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{
	struct strbuf str = STRBUF_INIT;
	const char *filename = git_path("BISECT_NAMES");
	FILE *fp = fopen(filename, "r");

	if (!fp)
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		die_errno("Could not open file '%s'", filename);
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	while (strbuf_getline(&str, fp, '\n') != EOF) {
		strbuf_trim(&str);
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		if (sq_dequote_to_argv_array(str.buf, array))
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			die("Badly quoted content in file '%s': %s",
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			    filename, str.buf);
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	}

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

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static char *join_sha1_array_hex(struct sha1_array *array, char delim)
{
	struct strbuf joined_hexs = STRBUF_INIT;
	int i;

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	for (i = 0; i < array->nr; i++) {
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		strbuf_addstr(&joined_hexs, sha1_to_hex(array->sha1[i]));
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		if (i + 1 < array->nr)
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			strbuf_addch(&joined_hexs, delim);
	}

	return strbuf_detach(&joined_hexs, NULL);
}

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/*
 * 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.
 */
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struct commit_list *filter_skipped(struct commit_list *list,
				   struct commit_list **tried,
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				   int show_all,
				   int *count,
				   int *skipped_first)
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{
	struct commit_list *filtered = NULL, **f = &filtered;

	*tried = NULL;

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

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	if (!skipped_revs.nr)
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		return list;

	while (list) {
		struct commit_list *next = list->next;
		list->next = NULL;
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		if (0 <= sha1_array_lookup(&skipped_revs,
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					   list->item->object.sha1)) {
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			if (skipped_first && !*skipped_first)
				*skipped_first = 1;
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			/* Move current to tried list */
			*tried = list;
			tried = &list->next;
		} else {
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			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;
			}
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			/* Move current to filtered list */
			*f = list;
			f = &list->next;
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			if (count)
				(*count)++;
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		}
		list = next;
	}

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

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	return filtered;
}
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#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.
 */
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static unsigned get_prn(unsigned count) {
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	count = count * 1103515245 + 12345;
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	return (count/65536) % PRN_MODULO;
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}

/*
 * 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)
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{
	struct commit_list *cur, *previous;
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	int prn, index, i;

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

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	if (!skipped_revs.nr)
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		return list;

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

	if (!skipped_first)
		return list;

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	return skip_away(list, count);
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}

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static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
			     const char *bad_format, const char *good_format,
			     int read_paths)
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{
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	struct argv_array rev_argv = ARGV_ARRAY_INIT;
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	int i;

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	init_revisions(revs, prefix);
	revs->abbrev = 0;
	revs->commit_format = CMIT_FMT_UNSPECIFIED;
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	/* rev_argv.argv[0] will be ignored by setup_revisions */
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	argv_array_push(&rev_argv, "bisect_rev_setup");
	argv_array_pushf(&rev_argv, bad_format, sha1_to_hex(current_bad_sha1));
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	for (i = 0; i < good_revs.nr; i++)
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		argv_array_pushf(&rev_argv, good_format,
				 sha1_to_hex(good_revs.sha1[i]));
	argv_array_push(&rev_argv, "--");
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	if (read_paths)
		read_bisect_paths(&rev_argv);
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	setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
	/* XXX leak rev_argv, as "revs" may still be pointing to it */
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}

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

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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);
}

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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;
}

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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)
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		die_errno("could not create file '%s'", filename);
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	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));
}

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static int bisect_checkout(char *bisect_rev_hex, int no_checkout)
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{

	mark_expected_rev(bisect_rev_hex);

	argv_checkout[2] = bisect_rev_hex;
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	if (no_checkout) {
		argv_update_ref[3] = bisect_rev_hex;
		if (run_command_v_opt(argv_update_ref, RUN_GIT_CMD))
			die("update-ref --no-deref HEAD failed on %s",
			    bisect_rev_hex);
	} else {
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		int res;
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		res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
		if (res)
			exit(res);
	}
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	argv_show_branch[1] = bisect_rev_hex;
	return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
}

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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)
{
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	int len = 1 + good_revs.nr;
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	struct commit **rev = xmalloc(len * sizeof(*rev));
	int i, n = 0;

	rev[n++] = get_commit_reference(current_bad_sha1);
722
	for (i = 0; i < good_revs.nr; i++)
723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748
		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);
}

749
static void handle_skipped_merge_base(const unsigned char *mb)
750 751 752 753 754
{
	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, ' ');

755
	warning("the merge base between %s and [%s] "
756 757 758
		"must be skipped.\n"
		"So we cannot be sure the first bad commit is "
		"between %s and %s.\n"
759
		"We continue anyway.",
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		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.
 */
773
static void check_merge_bases(int no_checkout)
774 775 776 777 778
{
	struct commit_list *result;
	int rev_nr;
	struct commit **rev = get_bad_and_good_commits(&rev_nr);

779
	result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 1);
780 781 782 783 784

	for (; result; result = result->next) {
		const unsigned char *mb = result->item->object.sha1;
		if (!hashcmp(mb, current_bad_sha1)) {
			handle_bad_merge_base();
785
		} else if (0 <= sha1_array_lookup(&good_revs, mb)) {
786
			continue;
787
		} else if (0 <= sha1_array_lookup(&skipped_revs, mb)) {
788 789 790
			handle_skipped_merge_base(mb);
		} else {
			printf("Bisecting: a merge base must be tested\n");
791
			exit(bisect_checkout(sha1_to_hex(mb), no_checkout));
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		}
	}

	free(rev);
	free_commit_list(result);
}

799
static int check_ancestors(const char *prefix)
800
{
801 802
	struct rev_info revs;
	struct object_array pending_copy;
803
	int res;
804

805
	bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
806

807
	/* Save pending objects, so they can be cleaned up later. */
808 809
	pending_copy = revs.pending;
	revs.leak_pending = 1;
810

811 812 813 814 815
	/*
	 * bisect_common calls prepare_revision_walk right away, which
	 * (together with .leak_pending = 1) makes us the sole owner of
	 * the list of pending objects.
	 */
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	bisect_common(&revs);
	res = (revs.commits != NULL);

	/* Clean up objects used, as they will be reused. */
820
	clear_commit_marks_for_object_array(&pending_copy, ALL_REV_FLAGS);
821
	free(pending_copy.objects);
822

823
	return res;
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}

/*
 * "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.
 */
834
static void check_good_are_ancestors_of_bad(const char *prefix, int no_checkout)
835
{
836
	char *filename = git_pathdup("BISECT_ANCESTORS_OK");
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	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))
845
		goto done;
846 847

	/* Bisecting with no good rev is ok. */
848
	if (good_revs.nr == 0)
849
		goto done;
850

851 852
	/* Check if all good revs are ancestor of the bad rev. */
	if (check_ancestors(prefix))
853
		check_merge_bases(no_checkout);
854 855 856 857 858 859 860 861

	/* 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);
862 863
 done:
	free(filename);
864 865
}

866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890
/*
 * 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);
}

891 892 893 894
/*
 * 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.
895 896 897
 *
 * If no_checkout is non-zero, the bisection process does not
 * checkout the trial commit but instead simply updates BISECT_HEAD.
898
 */
899
int bisect_next_all(const char *prefix, int no_checkout)
900 901 902
{
	struct rev_info revs;
	struct commit_list *tried;
903
	int reaches = 0, all = 0, nr, steps;
904 905 906
	const unsigned char *bisect_rev;
	char bisect_rev_hex[41];

907 908 909
	if (read_bisect_refs())
		die("reading bisect refs failed");

910
	check_good_are_ancestors_of_bad(prefix, no_checkout);
911

912 913
	bisect_rev_setup(&revs, prefix, "%s", "^%s", 1);
	revs.limited = 1;
914

915
	bisect_common(&revs);
916

917
	revs.commits = find_bisection(revs.commits, &reaches, &all,
918
				       !!skipped_revs.nr);
919
	revs.commits = managed_skipped(revs.commits, &tried);
920 921 922 923 924 925 926 927 928 929 930 931 932

	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);
	}

933 934 935 936 937 938
	if (!all) {
		fprintf(stderr, "No testable commit found.\n"
			"Maybe you started with bad path parameters?\n");
		exit(4);
	}

939 940 941 942 943
	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);
944
		printf("%s is the first bad commit\n", bisect_rev_hex);
945
		show_diff_tree(prefix, revs.commits->item);
946 947 948 949 950
		/* This means the bisection process succeeded. */
		exit(10);
	}

	nr = all - reaches - 1;
951 952 953 954
	steps = estimate_bisect_steps(all);
	printf("Bisecting: %d revision%s left to test after this "
	       "(roughly %d step%s)\n", nr, (nr == 1 ? "" : "s"),
	       steps, (steps == 1 ? "" : "s"));
955

956
	return bisect_checkout(bisect_rev_hex, no_checkout);
957 958
}

959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996
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;
}