Introduce --first-parent flag for git bisect

124 lines not on this page · raw message

index 8bad8d8391..a63af0505f 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all);
+		    int find_all, int first_parent_only);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

index f520111eda..d1a14596b2 100644
@@ -638,7 +638,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	if (bisect_list) {
 		int reaches, all;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all);
+		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index 6aa7f4f567..f0ad2603c1 100644
@@ -2869,9 +2869,6 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die("cannot use --grep-reflog without --walk-reflogs");
 
-	if (revs->first_parent_only && revs->bisect)
-		die(_("--first-parent is incompatible with --bisect"));
-
 	if (revs->line_level_traverse &&
 	    (revs->diffopt.output_format & ~(DIFF_FORMAT_PATCH | DIFF_FORMAT_NO_OUTPUT)))
 		die(_("-L does not yet support diff formats besides -p and -s"));

index 762f68c8e9..eee1f6f138 100644
@@ -463,6 +463,7 @@ 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 GIT_PATH_FUNC(git_path_head_name, "head-name")
 
 static void read_bisect_paths(struct argv_array *array)

@@ -984,6 +985,12 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
 	fclose(fp);
 }
 
+int read_first_parent_option(void)
+{
+	const char *filename = git_path_bisect_first_parent();
+	return !access(filename, F_OK);
+}
+
 /*
  * We use the convention that return BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND (-10) means
  * the bisection process finished successfully.

@@ -1000,7 +1007,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
+	int first_parent_only = read_first_parent_option();
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1144,6 +1151,7 @@ int bisect_clean_state(void)
 	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 head-name if it got left by an old version of git-bisect */
 	unlink_or_warn(git_path_head_name());
 	/*

index a63af0505f..8ee80f5b48 100644
@@ -66,6 +66,8 @@ int estimate_bisect_steps(int all);
 
 void read_bisect_terms(const char **bad, const char **good);
 
+int read_first_parent_option(void);
+
 int bisect_clean_state(void);
 
 #endif

index ec4996282e..1236f5df1d 100644
@@ -17,6 +17,7 @@ static GIT_PATH_FUNC(git_path_bisect_head, "BISECT_HEAD")
 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
 static GIT_PATH_FUNC(git_path_head_name, "head-name")
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
 
 static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --next-all [--no-checkout]"),

@@ -28,7 +29,7 @@ static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --bisect-next-check <good_term> <bad_term> [<term>]"),
 	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
 	N_("git bisect--helper --bisect-start [--term-{old,good}=<term> --term-{new,bad}=<term>]"
-					     "[--no-checkout] [<bad> [<good>...]] [--] [<paths>...]"),
+					    " [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]"),
 	NULL
 };
 

@@ -422,7 +423,7 @@ static int bisect_append_log_quoted(const char **argv)
 }
 
 static int bisect_start(struct bisect_terms *terms, int no_checkout,
-			const char **argv, int argc)
+			int first_parent_only, const char **argv, int argc)
 {
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
 	int flags, pathspec_pos, res = 0;

@@ -453,6 +454,8 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 			break;
 		} else if (!strcmp(arg, "--no-checkout")) {
 			no_checkout = 1;
+		} else if (!strcmp(arg, "--first-parent")) {
+			first_parent_only = 1;
 		} else if (!strcmp(arg, "--term-good") ||
 			 !strcmp(arg, "--term-old")) {
 			i++;

@@ -577,6 +580,9 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 	 */
 	write_file(git_path_bisect_start(), "%s\n", start_head.buf);
 
+	if (first_parent_only)
+		write_file(git_path_bisect_first_parent(), "\n");
+
 	if (no_checkout) {
 		if (get_oid(start_head.buf, &oid) < 0) {
 			res = error(_("invalid ref: '%s'"), start_head.buf);

@@ -632,7 +638,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		BISECT_TERMS,
 		BISECT_START
 	} cmdmode = 0;
-	int no_checkout = 0, res = 0, nolog = 0;
+	int no_checkout = 0, first_parent_only = 0, res = 0, nolog = 0;
 	struct option options[] = {
 		OPT_CMDMODE(0, "next-all", &cmdmode,
 			 N_("perform 'git bisect next'"), NEXT_ALL),

@@ -656,6 +662,8 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 			 N_("start the bisect session"), BISECT_START),
 		OPT_BOOL(0, "no-checkout", &no_checkout,
 			 N_("update BISECT_HEAD instead of checking out the current commit")),
+		OPT_BOOL(0, "first-parent", &first_parent_only,
+			 N_("only trace the first parent of merge commits")),
 		OPT_BOOL(0, "no-log", &nolog,
 			 N_("no log for BISECT_WRITE")),
 		OPT_END()

@@ -713,7 +721,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		break;
 	case BISECT_START:
 		set_terms(&terms, "bad", "good");
-		res = bisect_start(&terms, no_checkout, argv, argc);
+		res = bisect_start(&terms, no_checkout, first_parent_only, argv, argc);
 		break;
 	default:
 		return error("BUG: unknown subcommand '%d'", cmdmode);

index eee1f6f138..9599c58fd8 100644
@@ -37,7 +37,7 @@ static const char *term_good;
  * We care just barely enough to avoid recursing for
  * non-merge entries.
  */
-static int count_distance(struct commit_list *entry, int first_parent_only)
+static int count_distance(struct commit_list *entry, unsigned bisect_flags)
 {
 	int nr = 0;
 

@@ -52,10 +52,10 @@ static int count_distance(struct commit_list *entry, int first_parent_only)
 		commit->object.flags |= COUNTED;
 		p = commit->parents;
 		entry = p;
-		if (p && !first_parent_only) {
+		if (p && !(bisect_flags & BISECT_FIRST_PARENT)) {
 			p = p->next;
 			while (p) {
-				nr += count_distance(p, first_parent_only);
+				nr += count_distance(p, bisect_flags);
 				p = p->next;
 			}
 		}

@@ -88,7 +88,7 @@ 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, int first_parent_only)
+static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
 {
 	struct commit_list *p;
 	int count;

@@ -96,7 +96,7 @@ static int count_interesting_parents(struct commit *commit, int first_parent_onl
 	for (count = 0, p = commit->parents; p; p = p->next) {
 		if (!(p->item->object.flags & UNINTERESTING))
 			count++;
-		if (first_parent_only)
+		if (bisect_flags & BISECT_FIRST_PARENT)
 			break;
 	}
 	return count;

@@ -260,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all, int first_parent_only)
+					     unsigned bisect_flags)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -272,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit, first_parent_only)) {
+		switch (count_interesting_parents(commit, bisect_flags)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -315,11 +315,11 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
-		weight_set(p, count_distance(p, first_parent_only));
+		weight_set(p, count_distance(p, bisect_flags));
 		clear_distance(list);
 
 		/* Does it happen to be at exactly half-way? */
-		if (!find_all && halfway(p, nr))
+		if (!(bisect_flags & BISECT_FIND_ALL) && halfway(p, nr))
 			return p;
 		counted++;
 	}

@@ -342,7 +342,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			for (q = p->item->parents; q; q = q->next) {
 				if (!(q->item->object.flags & UNINTERESTING) && 0 <= weight(q)) {
 					break;
-				} else if (first_parent_only) {
+				} else if (bisect_flags & BISECT_FIRST_PARENT) {
 					q = NULL;
 					break;
 				}

@@ -365,21 +365,21 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 				weight_set(p, weight(q));
 
 			/* Does it happen to be at exactly half-way? */
-			if (!find_all && halfway(p, nr))
+			if (!(bisect_flags & BISECT_FIND_ALL) && halfway(p, nr))
 				return p;
 		}
 	}
 
 	show_list("bisection 2 counted all", counted, nr, list);
 
-	if (!find_all)
+	if (!(bisect_flags & BISECT_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 first_parent_only)
+		    int *all, unsigned bisect_flags)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -415,9 +415,9 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
+	best = do_find_bisection(list, nr, weights, bisect_flags);
 	if (best) {
-		if (!find_all) {
+		if (!(bisect_flags & BISECT_FIND_ALL)) {
 			list->item = best->item;
 			free_commit_list(list->next);
 			best = list;

@@ -1007,23 +1007,30 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = read_first_parent_option();
+	unsigned bisect_flags = 0;
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())
 		die(_("reading bisect refs failed"));
 
+	if (read_first_parent_option())
+		bisect_flags |= BISECT_FIRST_PARENT;
+
+	if (!!skipped_revs.nr)
+		bisect_flags |= BISECT_FIND_ALL;
+
 	res = check_good_are_ancestors_of_bad(r, prefix, no_checkout);
 	if (res)
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
-	revs.first_parent_only = first_parent_only;
+
+	revs.first_parent_only = !!(bisect_flags & BISECT_FIRST_PARENT);
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
+	find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 8ee80f5b48..402ddcfb5e 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all, int first_parent_only);
+		    unsigned bisect_flags);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

@@ -23,6 +23,9 @@ struct commit_list *filter_skipped(struct commit_list *list,
 #define BISECT_SHOW_ALL		(1<<0)
 #define REV_LIST_QUIET		(1<<1)
 
+#define BISECT_FIND_ALL		(1u<<0)
+#define BISECT_FIRST_PARENT	(1u<<1)
+
 struct rev_list_info {
 	struct rev_info *revs;
 	int flags;

index d1a14596b2..1536ea6f28 100644
@@ -637,8 +637,15 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 
 	if (bisect_list) {
 		int reaches, all;
+		unsigned bisect_flags = 0;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
+		if (bisect_find_all)
+			bisect_flags |= BISECT_FIND_ALL;
+
+		if (revs.first_parent_only)
+			bisect_flags |= BISECT_FIRST_PARENT;
+
+		find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index 762f68c8e9..a11fdb1473 100644
@@ -37,7 +37,7 @@ static const char *term_good;
  * We care just barely enough to avoid recursing for
  * non-merge entries.
  */
-static int count_distance(struct commit_list *entry, int first_parent_only)
+static int count_distance(struct commit_list *entry)
 {
 	int nr = 0;
 

@@ -52,10 +52,10 @@ static int count_distance(struct commit_list *entry, int first_parent_only)
 		commit->object.flags |= COUNTED;
 		p = commit->parents;
 		entry = p;
-		if (p && !first_parent_only) {
+		if (p) {
 			p = p->next;
 			while (p) {
-				nr += count_distance(p, first_parent_only);
+				nr += count_distance(p);
 				p = p->next;
 			}
 		}

@@ -315,7 +315,9 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
-		weight_set(p, count_distance(p, first_parent_only));
+		if (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 exactly half-way? */

@@ -331,21 +333,16 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			struct commit_list *q;
 			unsigned flags = p->item->object.flags;
 
-			/* if commit p has already been weighted, continue. */
 			if (0 <= weight(p))
 				continue;
 
-			/*
-			 * otherwise, find the first interesting
-			 * already-weighted parent of p and store as q.
-			 */
-			for (q = p->item->parents; q; q = q->next) {
-				if (!(q->item->object.flags & UNINTERESTING) && 0 <= weight(q)) {
-					break;
-				} else if (first_parent_only) {
-					q = NULL;
+			for (q = p->item->parents;
+			     q;
+			     q = first_parent_only ? NULL : q->next) {
+				if (q->item->object.flags & UNINTERESTING)
+					continue;
+				if (0 <= weight(q))
 					break;
-				}
 			}
 			if (!q)
 				continue;

index d5e830410f..a11fdb1473 100644
@@ -88,15 +88,16 @@ 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)
+static int count_interesting_parents(struct commit *commit, int first_parent_only)
 {
 	struct commit_list *p;
 	int count;
 
 	for (count = 0, p = commit->parents; p; p = p->next) {
-		if (p->item->object.flags & UNINTERESTING)
-			continue;
-		count++;
+		if (!(p->item->object.flags & UNINTERESTING))
+			count++;
+		if (first_parent_only)
+			break;
 	}
 	return count;
 }

@@ -259,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all)
+					     int find_all, int first_parent_only)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -271,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit)) {
+		switch (count_interesting_parents(commit, first_parent_only)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -314,6 +315,8 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
+		if (first_parent_only)
+			BUG("shouldn't be calling count-distance in fp mode");
 		weight_set(p, count_distance(p));
 		clear_distance(list);
 

@@ -332,7 +335,10 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 			if (0 <= weight(p))
 				continue;
-			for (q = p->item->parents; q; q = q->next) {
+
+			for (q = p->item->parents;
+			     q;
+			     q = first_parent_only ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -370,7 +376,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 }
 
 void find_bisection(struct commit_list **commit_list, int *reaches,
-		    int *all, int find_all)
+		    int *all, int find_all, int first_parent_only)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -406,7 +412,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all);
+	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
 	if (best) {
 		if (!find_all) {
 			list->item = best->item;

@@ -991,6 +997,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
+	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1001,11 +1008,12 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
+	revs.first_parent_only = first_parent_only;
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
+	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 8bad8d8391..a63af0505f 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all);
+		    int find_all, int first_parent_only);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

index f520111eda..d1a14596b2 100644
@@ -638,7 +638,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	if (bisect_list) {
 		int reaches, all;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all);
+		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index 6aa7f4f567..f0ad2603c1 100644
@@ -2869,9 +2869,6 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die("cannot use --grep-reflog without --walk-reflogs");
 
-	if (revs->first_parent_only && revs->bisect)
-		die(_("--first-parent is incompatible with --bisect"));
-
 	if (revs->line_level_traverse &&
 	    (revs->diffopt.output_format & ~(DIFF_FORMAT_PATCH | DIFF_FORMAT_NO_OUTPUT)))
 		die(_("-L does not yet support diff formats besides -p and -s"));

index a11fdb1473..b495a19192 100644
@@ -460,6 +460,7 @@ 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 GIT_PATH_FUNC(git_path_head_name, "head-name")
 
 static void read_bisect_paths(struct argv_array *array)

@@ -981,6 +982,12 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
 	fclose(fp);
 }
 
+int read_first_parent_option(void)
+{
+	const char *filename = git_path_bisect_first_parent();
+	return !access(filename, F_OK);
+}
+
 /*
  * We use the convention that return BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND (-10) means
  * the bisection process finished successfully.

@@ -997,7 +1004,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
+	int first_parent_only = read_first_parent_option();
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1141,6 +1148,7 @@ int bisect_clean_state(void)
 	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 head-name if it got left by an old version of git-bisect */
 	unlink_or_warn(git_path_head_name());
 	/*

index a63af0505f..8ee80f5b48 100644
@@ -66,6 +66,8 @@ int estimate_bisect_steps(int all);
 
 void read_bisect_terms(const char **bad, const char **good);
 
+int read_first_parent_option(void);
+
 int bisect_clean_state(void);
 
 #endif

index ec4996282e..1236f5df1d 100644
@@ -17,6 +17,7 @@ static GIT_PATH_FUNC(git_path_bisect_head, "BISECT_HEAD")
 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
 static GIT_PATH_FUNC(git_path_head_name, "head-name")
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
 
 static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --next-all [--no-checkout]"),

@@ -28,7 +29,7 @@ static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --bisect-next-check <good_term> <bad_term> [<term>]"),
 	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
 	N_("git bisect--helper --bisect-start [--term-{old,good}=<term> --term-{new,bad}=<term>]"
-					     "[--no-checkout] [<bad> [<good>...]] [--] [<paths>...]"),
+					    " [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]"),
 	NULL
 };
 

@@ -422,7 +423,7 @@ static int bisect_append_log_quoted(const char **argv)
 }
 
 static int bisect_start(struct bisect_terms *terms, int no_checkout,
-			const char **argv, int argc)
+			int first_parent_only, const char **argv, int argc)
 {
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
 	int flags, pathspec_pos, res = 0;

@@ -453,6 +454,8 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 			break;
 		} else if (!strcmp(arg, "--no-checkout")) {
 			no_checkout = 1;
+		} else if (!strcmp(arg, "--first-parent")) {
+			first_parent_only = 1;
 		} else if (!strcmp(arg, "--term-good") ||
 			 !strcmp(arg, "--term-old")) {
 			i++;

@@ -577,6 +580,9 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 	 */
 	write_file(git_path_bisect_start(), "%s\n", start_head.buf);
 
+	if (first_parent_only)
+		write_file(git_path_bisect_first_parent(), "\n");
+
 	if (no_checkout) {
 		if (get_oid(start_head.buf, &oid) < 0) {
 			res = error(_("invalid ref: '%s'"), start_head.buf);

@@ -632,7 +638,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		BISECT_TERMS,
 		BISECT_START
 	} cmdmode = 0;
-	int no_checkout = 0, res = 0, nolog = 0;
+	int no_checkout = 0, first_parent_only = 0, res = 0, nolog = 0;
 	struct option options[] = {
 		OPT_CMDMODE(0, "next-all", &cmdmode,
 			 N_("perform 'git bisect next'"), NEXT_ALL),

@@ -656,6 +662,8 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 			 N_("start the bisect session"), BISECT_START),
 		OPT_BOOL(0, "no-checkout", &no_checkout,
 			 N_("update BISECT_HEAD instead of checking out the current commit")),
+		OPT_BOOL(0, "first-parent", &first_parent_only,
+			 N_("only trace the first parent of merge commits")),
 		OPT_BOOL(0, "no-log", &nolog,
 			 N_("no log for BISECT_WRITE")),
 		OPT_END()

@@ -713,7 +721,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		break;
 	case BISECT_START:
 		set_terms(&terms, "bad", "good");
-		res = bisect_start(&terms, no_checkout, argv, argc);
+		res = bisect_start(&terms, no_checkout, first_parent_only, argv, argc);
 		break;
 	default:
 		return error("BUG: unknown subcommand '%d'", cmdmode);

index b495a19192..07a7760a72 100644
@@ -88,7 +88,7 @@ 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, int first_parent_only)
+static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
 {
 	struct commit_list *p;
 	int count;

@@ -96,7 +96,7 @@ static int count_interesting_parents(struct commit *commit, int first_parent_onl
 	for (count = 0, p = commit->parents; p; p = p->next) {
 		if (!(p->item->object.flags & UNINTERESTING))
 			count++;
-		if (first_parent_only)
+		if (bisect_flags & BISECT_FIRST_PARENT)
 			break;
 	}
 	return count;

@@ -260,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all, int first_parent_only)
+					     unsigned bisect_flags)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -272,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit, first_parent_only)) {
+		switch (count_interesting_parents(commit, bisect_flags)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -315,13 +315,13 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
-		if (first_parent_only)
+		if (bisect_flags & BISECT_FIRST_PARENT)
 			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 exactly half-way? */
-		if (!find_all && halfway(p, nr))
+		if (!(bisect_flags & BISECT_FIND_ALL) && halfway(p, nr))
 			return p;
 		counted++;
 	}

@@ -338,7 +338,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 			for (q = p->item->parents;
 			     q;
-			     q = first_parent_only ? NULL : q->next) {
+			     q = bisect_flags & BISECT_FIRST_PARENT ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -362,21 +362,21 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 				weight_set(p, weight(q));
 
 			/* Does it happen to be at exactly half-way? */
-			if (!find_all && halfway(p, nr))
+			if (!(bisect_flags & BISECT_FIND_ALL) && halfway(p, nr))
 				return p;
 		}
 	}
 
 	show_list("bisection 2 counted all", counted, nr, list);
 
-	if (!find_all)
+	if (!(bisect_flags & BISECT_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 first_parent_only)
+		    int *all, unsigned bisect_flags)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -412,9 +412,9 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
+	best = do_find_bisection(list, nr, weights, bisect_flags);
 	if (best) {
-		if (!find_all) {
+		if (!(bisect_flags & BISECT_FIND_ALL)) {
 			list->item = best->item;
 			free_commit_list(list->next);
 			best = list;

@@ -1004,23 +1004,30 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = read_first_parent_option();
+	unsigned bisect_flags = 0;
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())
 		die(_("reading bisect refs failed"));
 
+	if (read_first_parent_option())
+		bisect_flags |= BISECT_FIRST_PARENT;
+
+	if (!!skipped_revs.nr)
+		bisect_flags |= BISECT_FIND_ALL;
+
 	res = check_good_are_ancestors_of_bad(r, prefix, no_checkout);
 	if (res)
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
-	revs.first_parent_only = first_parent_only;
+
+	revs.first_parent_only = !!(bisect_flags & BISECT_FIRST_PARENT);
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
+	find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 8ee80f5b48..402ddcfb5e 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all, int first_parent_only);
+		    unsigned bisect_flags);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

@@ -23,6 +23,9 @@ struct commit_list *filter_skipped(struct commit_list *list,
 #define BISECT_SHOW_ALL		(1<<0)
 #define REV_LIST_QUIET		(1<<1)
 
+#define BISECT_FIND_ALL		(1u<<0)
+#define BISECT_FIRST_PARENT	(1u<<1)
+
 struct rev_list_info {
 	struct rev_info *revs;
 	int flags;

index d1a14596b2..1536ea6f28 100644
@@ -637,8 +637,15 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 
 	if (bisect_list) {
 		int reaches, all;
+		unsigned bisect_flags = 0;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
+		if (bisect_find_all)
+			bisect_flags |= BISECT_FIND_ALL;
+
+		if (revs.first_parent_only)
+			bisect_flags |= BISECT_FIRST_PARENT;
+
+		find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index d5e830410f..a11fdb1473 100644
@@ -88,15 +88,16 @@ 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)
+static int count_interesting_parents(struct commit *commit, int first_parent_only)
 {
 	struct commit_list *p;
 	int count;
 
 	for (count = 0, p = commit->parents; p; p = p->next) {
-		if (p->item->object.flags & UNINTERESTING)
-			continue;
-		count++;
+		if (!(p->item->object.flags & UNINTERESTING))
+			count++;
+		if (first_parent_only)
+			break;
 	}
 	return count;
 }

@@ -259,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all)
+					     int find_all, int first_parent_only)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -271,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit)) {
+		switch (count_interesting_parents(commit, first_parent_only)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -314,6 +315,8 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
+		if (first_parent_only)
+			BUG("shouldn't be calling count-distance in fp mode");
 		weight_set(p, count_distance(p));
 		clear_distance(list);
 

@@ -332,7 +335,10 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 			if (0 <= weight(p))
 				continue;
-			for (q = p->item->parents; q; q = q->next) {
+
+			for (q = p->item->parents;
+			     q;
+			     q = first_parent_only ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -370,7 +376,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 }
 
 void find_bisection(struct commit_list **commit_list, int *reaches,
-		    int *all, int find_all)
+		    int *all, int find_all, int first_parent_only)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -406,7 +412,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all);
+	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
 	if (best) {
 		if (!find_all) {
 			list->item = best->item;

@@ -991,6 +997,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
+	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1001,11 +1008,12 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
+	revs.first_parent_only = first_parent_only;
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
+	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 8bad8d8391..a63af0505f 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all);
+		    int find_all, int first_parent_only);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

index f520111eda..d1a14596b2 100644
@@ -638,7 +638,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	if (bisect_list) {
 		int reaches, all;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all);
+		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index 6aa7f4f567..f0ad2603c1 100644
@@ -2869,9 +2869,6 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die("cannot use --grep-reflog without --walk-reflogs");
 
-	if (revs->first_parent_only && revs->bisect)
-		die(_("--first-parent is incompatible with --bisect"));
-
 	if (revs->line_level_traverse &&
 	    (revs->diffopt.output_format & ~(DIFF_FORMAT_PATCH | DIFF_FORMAT_NO_OUTPUT)))
 		die(_("-L does not yet support diff formats besides -p and -s"));

index afbb5aea32..b14a2edc38 100644
@@ -88,7 +88,7 @@ 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, int first_parent_only)
+static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
 {
 	struct commit_list *p;
 	int count;

@@ -96,7 +96,7 @@ static int count_interesting_parents(struct commit *commit, int first_parent_onl
 	for (count = 0, p = commit->parents; p; p = p->next) {
 		if (!(p->item->object.flags & UNINTERESTING))
 			count++;
-		if (first_parent_only)
+		if (bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY)
 			break;
 	}
 	return count;

@@ -136,7 +136,7 @@ static void show_list(const char *debug, int counted, int nr,
 	for (p = list; p; p = p->next) {
 		struct commit_list *pp;
 		struct commit *commit = p->item;
-		unsigned flags = commit->object.flags;
+		unsigned commit_flags = commit->object.flags;
 		enum object_type type;
 		unsigned long size;
 		char *buf = read_object_file(&commit->object.oid, &type,

@@ -145,9 +145,9 @@ static void show_list(const char *debug, int counted, int nr,
 		int subject_len;
 
 		fprintf(stderr, "%c%c%c ",
-			(flags & TREESAME) ? ' ' : 'T',
-			(flags & UNINTERESTING) ? 'U' : ' ',
-			(flags & COUNTED) ? '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

@@ -172,9 +172,9 @@ static struct commit_list *best_bisection(struct commit_list *list, int nr)
 	best = list;
 	for (p = list; p; p = p->next) {
 		int distance;
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
-		if (flags & TREESAME)
+		if (commit_flags & TREESAME)
 			continue;
 		distance = weight(p);
 		if (nr - distance < distance)

@@ -213,9 +213,9 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
 
 	for (p = list, cnt = 0; p; p = p->next) {
 		int distance;
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
-		if (flags & TREESAME)
+		if (commit_flags & TREESAME)
 			continue;
 		distance = weight(p);
 		if (nr - distance < distance)

@@ -260,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all, int first_parent_only)
+					     unsigned bisect_flags)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -269,12 +269,12 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 	for (n = 0, p = list; p; p = p->next) {
 		struct commit *commit = p->item;
-		unsigned flags = commit->object.flags;
+		unsigned commit_flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit, first_parent_only)) {
+		switch (count_interesting_parents(commit, bisect_flags)) {
 		case 0:
-			if (!(flags & TREESAME)) {
+			if (!(commit_flags & TREESAME)) {
 				weight_set(p, 1);
 				counted++;
 				show_list("bisection 2 count one",

@@ -315,13 +315,13 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
-		if (first_parent_only)
+		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 exactly half-way? */
-		if (!find_all && halfway(p, nr))
+		if (!(bisect_flags & FIND_BISECTION_ALL) && halfway(p, nr))
 			return p;
 		counted++;
 	}

@@ -331,14 +331,14 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 	while (counted < nr) {
 		for (p = list; p; p = p->next) {
 			struct commit_list *q;
-			unsigned flags = p->item->object.flags;
+			unsigned commit_flags = p->item->object.flags;
 
 			if (0 <= weight(p))
 				continue;
 
 			for (q = p->item->parents;
 			     q;
-			     q = first_parent_only ? NULL : q->next) {
+			     q = bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -352,7 +352,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			 * add one for p itself if p is to be counted,
 			 * otherwise inherit it from q directly.
 			 */
-			if (!(flags & TREESAME)) {
+			if (!(commit_flags & TREESAME)) {
 				weight_set(p, weight(q)+1);
 				counted++;
 				show_list("bisection 2 count one",

@@ -362,21 +362,21 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 				weight_set(p, weight(q));
 
 			/* Does it happen to be at exactly half-way? */
-			if (!find_all && halfway(p, nr))
+			if (!(bisect_flags & FIND_BISECTION_ALL) && halfway(p, nr))
 				return p;
 		}
 	}
 
 	show_list("bisection 2 counted all", counted, nr, list);
 
-	if (!find_all)
+	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, int find_all, int first_parent_only)
+		    int *all, unsigned bisect_flags)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -392,16 +392,16 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	for (nr = on_list = 0, last = NULL, p = *commit_list;
 	     p;
 	     p = next) {
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
 		next = p->next;
-		if (flags & UNINTERESTING) {
+		if (commit_flags & UNINTERESTING) {
 			free(p);
 			continue;
 		}
 		p->next = last;
 		last = p;
-		if (!(flags & TREESAME))
+		if (!(commit_flags & TREESAME))
 			nr++;
 		on_list++;
 	}

@@ -412,9 +412,9 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
+	best = do_find_bisection(list, nr, weights, bisect_flags);
 	if (best) {
-		if (!find_all) {
+		if (!(bisect_flags & FIND_BISECTION_ALL)) {
 			list->item = best->item;
 			free_commit_list(list->next);
 			best = list;

@@ -1004,23 +1004,30 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = read_first_parent_option();
+	unsigned bisect_flags = 0;
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())
 		die(_("reading bisect refs failed"));
 
+	if (read_first_parent_option())
+		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)
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
-	revs.first_parent_only = first_parent_only;
+
+	revs.first_parent_only = !!(bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY);
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
+	find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index a63af0505f..b673fd9ed2 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all, int first_parent_only);
+		    unsigned bisect_flags);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

@@ -23,6 +23,9 @@ struct commit_list *filter_skipped(struct commit_list *list,
 #define BISECT_SHOW_ALL		(1<<0)
 #define REV_LIST_QUIET		(1<<1)
 
+#define FIND_BISECTION_ALL			(1u<<0)
+#define FIND_BISECTION_FIRST_PARENT_ONLY	(1u<<1)
+
 struct rev_list_info {
 	struct rev_info *revs;
 	int flags;

index d1a14596b2..25c6c3b38d 100644
@@ -637,8 +637,15 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 
 	if (bisect_list) {
 		int reaches, all;
+		unsigned bisect_flags = 0;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
+		if (bisect_find_all)
+			bisect_flags |= FIND_BISECTION_ALL;
+
+		if (revs.first_parent_only)
+			bisect_flags |= FIND_BISECTION_FIRST_PARENT_ONLY;
+
+		find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index a11fdb1473..afbb5aea32 100644
@@ -460,6 +460,7 @@ 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 GIT_PATH_FUNC(git_path_head_name, "head-name")
 
 static void read_bisect_paths(struct argv_array *array)

@@ -981,6 +982,12 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
 	fclose(fp);
 }
 
+static int read_first_parent_option(void)
+{
+	const char *filename = git_path_bisect_first_parent();
+	return !access(filename, F_OK);
+}
+
 /*
  * We use the convention that return BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND (-10) means
  * the bisection process finished successfully.

@@ -997,7 +1004,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
-	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
+	int first_parent_only = read_first_parent_option();
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1141,6 +1148,7 @@ int bisect_clean_state(void)
 	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 head-name if it got left by an old version of git-bisect */
 	unlink_or_warn(git_path_head_name());
 	/*

index ec4996282e..9273140f0b 100644
@@ -17,6 +17,7 @@ static GIT_PATH_FUNC(git_path_bisect_head, "BISECT_HEAD")
 static GIT_PATH_FUNC(git_path_bisect_log, "BISECT_LOG")
 static GIT_PATH_FUNC(git_path_head_name, "head-name")
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
 
 static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --next-all [--no-checkout]"),

@@ -28,7 +29,7 @@ static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --bisect-next-check <good_term> <bad_term> [<term>]"),
 	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
 	N_("git bisect--helper --bisect-start [--term-{old,good}=<term> --term-{new,bad}=<term>]"
-					     "[--no-checkout] [<bad> [<good>...]] [--] [<paths>...]"),
+					    " [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]"),
 	NULL
 };
 

@@ -422,7 +423,7 @@ static int bisect_append_log_quoted(const char **argv)
 }
 
 static int bisect_start(struct bisect_terms *terms, int no_checkout,
-			const char **argv, int argc)
+			int first_parent_only, const char **argv, int argc)
 {
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
 	int flags, pathspec_pos, res = 0;

@@ -577,6 +578,9 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 	 */
 	write_file(git_path_bisect_start(), "%s\n", start_head.buf);
 
+	if (first_parent_only)
+		write_file(git_path_bisect_first_parent(), "\n");
+
 	if (no_checkout) {
 		if (get_oid(start_head.buf, &oid) < 0) {
 			res = error(_("invalid ref: '%s'"), start_head.buf);

@@ -632,7 +636,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		BISECT_TERMS,
 		BISECT_START
 	} cmdmode = 0;
-	int no_checkout = 0, res = 0, nolog = 0;
+	int no_checkout = 0, first_parent_only = 0, res = 0, nolog = 0;
 	struct option options[] = {
 		OPT_CMDMODE(0, "next-all", &cmdmode,
 			 N_("perform 'git bisect next'"), NEXT_ALL),

@@ -656,6 +660,8 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 			 N_("start the bisect session"), BISECT_START),
 		OPT_BOOL(0, "no-checkout", &no_checkout,
 			 N_("update BISECT_HEAD instead of checking out the current commit")),
+		OPT_BOOL(0, "first-parent", &first_parent_only,
+			 N_("only trace the first parent of merge commits")),
 		OPT_BOOL(0, "no-log", &nolog,
 			 N_("no log for BISECT_WRITE")),
 		OPT_END()

@@ -713,7 +719,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		break;
 	case BISECT_START:
 		set_terms(&terms, "bad", "good");
-		res = bisect_start(&terms, no_checkout, argv, argc);
+		res = bisect_start(&terms, no_checkout, first_parent_only, argv, argc);
 		break;
 	default:
 		return error("BUG: unknown subcommand '%d'", cmdmode);

index d5e830410f..a11fdb1473 100644
@@ -88,15 +88,16 @@ 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)
+static int count_interesting_parents(struct commit *commit, int first_parent_only)
 {
 	struct commit_list *p;
 	int count;
 
 	for (count = 0, p = commit->parents; p; p = p->next) {
-		if (p->item->object.flags & UNINTERESTING)
-			continue;
-		count++;
+		if (!(p->item->object.flags & UNINTERESTING))
+			count++;
+		if (first_parent_only)
+			break;
 	}
 	return count;
 }

@@ -259,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all)
+					     int find_all, int first_parent_only)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -271,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit)) {
+		switch (count_interesting_parents(commit, first_parent_only)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -314,6 +315,8 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
+		if (first_parent_only)
+			BUG("shouldn't be calling count-distance in fp mode");
 		weight_set(p, count_distance(p));
 		clear_distance(list);
 

@@ -332,7 +335,10 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 			if (0 <= weight(p))
 				continue;
-			for (q = p->item->parents; q; q = q->next) {
+
+			for (q = p->item->parents;
+			     q;
+			     q = first_parent_only ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -370,7 +376,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 }
 
 void find_bisection(struct commit_list **commit_list, int *reaches,
-		    int *all, int find_all)
+		    int *all, int find_all, int first_parent_only)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -406,7 +412,7 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all);
+	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
 	if (best) {
 		if (!find_all) {
 			list->item = best->item;

@@ -991,6 +997,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
+	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1001,11 +1008,12 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
+	revs.first_parent_only = first_parent_only;
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr);
+	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 8bad8d8391..a63af0505f 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all);
+		    int find_all, int first_parent_only);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

index f520111eda..d1a14596b2 100644
@@ -638,7 +638,7 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 	if (bisect_list) {
 		int reaches, all;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all);
+		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index 6de29cdf7a..e628d5ea56 100644
@@ -2891,9 +2891,6 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
 		die("cannot use --grep-reflog without --walk-reflogs");
 
-	if (revs->first_parent_only && revs->bisect)
-		die(_("--first-parent is incompatible with --bisect"));
-
 	if (revs->line_level_traverse &&
 	    (revs->diffopt.output_format & ~(DIFF_FORMAT_PATCH | DIFF_FORMAT_NO_OUTPUT)))
 		die(_("-L does not yet support diff formats besides -p and -s"));

index a11fdb1473..950ff6f533 100644
@@ -989,7 +989,7 @@ void read_bisect_terms(const char **read_bad, const char **read_good)
  * If no_checkout is non-zero, the bisection process does not
  * checkout the trial commit but instead simply updates BISECT_HEAD.
  */
-enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
+enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 {
 	struct rev_info revs;
 	struct commit_list *tried;

@@ -997,6 +997,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix, int
 	enum bisect_error res = BISECT_OK;
 	struct object_id *bisect_rev;
 	char *steps_msg;
+	int no_checkout = ref_exists("BISECT_HEAD");
 	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
 
 	read_bisect_terms(&term_bad, &term_good);

index a63af0505f..7f30b94db3 100644
@@ -58,9 +58,7 @@ enum bisect_error {
 	BISECT_INTERNAL_SUCCESS_MERGE_BASE = -11
 };
 
-enum bisect_error bisect_next_all(struct repository *r,
-		    const char *prefix,
-		    int no_checkout);
+enum bisect_error bisect_next_all(struct repository *r, const char *prefix);
 
 int estimate_bisect_steps(int all);
 

index 73f9324ad7..95a15b918f 100644
@@ -18,7 +18,7 @@ static GIT_PATH_FUNC(git_path_head_name, "head-name")
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
 
 static const char * const git_bisect_helper_usage[] = {
-	N_("git bisect--helper --next-all [--no-checkout]"),
+	N_("git bisect--helper --next-all"),
 	N_("git bisect--helper --write-terms <bad_term> <good_term>"),
 	N_("git bisect--helper --bisect-clean-state"),
 	N_("git bisect--helper --bisect-reset [<commit>]"),

@@ -420,9 +420,9 @@ static int bisect_append_log_quoted(const char **argv)
 	return res;
 }
 
-static int bisect_start(struct bisect_terms *terms, int no_checkout,
-			const char **argv, int argc)
+static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 {
+	int no_checkout = 0;
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
 	int flags, pathspec_pos, res = 0;
 	struct string_list revs = STRING_LIST_INIT_DUP;

@@ -631,7 +631,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		BISECT_TERMS,
 		BISECT_START
 	} cmdmode = 0;
-	int no_checkout = 0, res = 0, nolog = 0;
+	int res = 0, nolog = 0;
 	struct option options[] = {
 		OPT_CMDMODE(0, "next-all", &cmdmode,
 			 N_("perform 'git bisect next'"), NEXT_ALL),

@@ -653,8 +653,6 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 			 N_("print out the bisect terms"), BISECT_TERMS),
 		OPT_CMDMODE(0, "bisect-start", &cmdmode,
 			 N_("start the bisect session"), BISECT_START),
-		OPT_BOOL(0, "no-checkout", &no_checkout,
-			 N_("update BISECT_HEAD instead of checking out the current commit")),
 		OPT_BOOL(0, "no-log", &nolog,
 			 N_("no log for BISECT_WRITE")),
 		OPT_END()

@@ -670,7 +668,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 
 	switch (cmdmode) {
 	case NEXT_ALL:
-		res = bisect_next_all(the_repository, prefix, no_checkout);
+		res = bisect_next_all(the_repository, prefix);
 		break;
 	case WRITE_TERMS:
 		if (argc != 2)

@@ -712,7 +710,7 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
 		break;
 	case BISECT_START:
 		set_terms(&terms, "bad", "good");
-		res = bisect_start(&terms, no_checkout, argv, argc);
+		res = bisect_start(&terms, argv, argc);
 		break;
 	default:
 		return error("BUG: unknown subcommand '%d'", cmdmode);

index 950ff6f533..bc4241b51f 100644
@@ -15,6 +15,7 @@
 #include "commit-slab.h"
 #include "commit-reach.h"
 #include "object-store.h"
+#include "dir.h"
 
 static struct oid_array good_revs;
 static struct oid_array skipped_revs;

@@ -460,6 +461,7 @@ 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 GIT_PATH_FUNC(git_path_head_name, "head-name")
 
 static void read_bisect_paths(struct argv_array *array)

@@ -998,7 +1000,7 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 	struct object_id *bisect_rev;
 	char *steps_msg;
 	int no_checkout = ref_exists("BISECT_HEAD");
-	int first_parent_only = 0; /* TODO: pass --first-parent flag from git bisect start */
+	int first_parent_only = file_exists(git_path_bisect_first_parent());
 
 	read_bisect_terms(&term_bad, &term_good);
 	if (read_bisect_refs())

@@ -1142,6 +1144,7 @@ int bisect_clean_state(void)
 	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 head-name if it got left by an old version of git-bisect */
 	unlink_or_warn(git_path_head_name());
 	/*

index 95a15b918f..a055147f19 100644
@@ -16,6 +16,7 @@ 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_head_name, "head-name")
 static GIT_PATH_FUNC(git_path_bisect_names, "BISECT_NAMES")
+static GIT_PATH_FUNC(git_path_bisect_first_parent, "BISECT_FIRST_PARENT")
 
 static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --next-all"),

@@ -27,7 +28,7 @@ static const char * const git_bisect_helper_usage[] = {
 	N_("git bisect--helper --bisect-next-check <good_term> <bad_term> [<term>]"),
 	N_("git bisect--helper --bisect-terms [--term-good | --term-old | --term-bad | --term-new]"),
 	N_("git bisect--helper --bisect-start [--term-{old,good}=<term> --term-{new,bad}=<term>]"
-					     "[--no-checkout] [<bad> [<good>...]] [--] [<paths>...]"),
+					    " [--no-checkout] [--first-parent] [<bad> [<good>...]] [--] [<paths>...]"),
 	NULL
 };
 

@@ -423,6 +424,7 @@ static int bisect_append_log_quoted(const char **argv)
 static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 {
 	int no_checkout = 0;
+	int first_parent_only = 0;
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
 	int flags, pathspec_pos, res = 0;
 	struct string_list revs = STRING_LIST_INIT_DUP;

@@ -452,6 +454,8 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 			break;
 		} else if (!strcmp(arg, "--no-checkout")) {
 			no_checkout = 1;
+		} else if (!strcmp(arg, "--first-parent")) {
+			first_parent_only = 1;
 		} else if (!strcmp(arg, "--term-good") ||
 			 !strcmp(arg, "--term-old")) {
 			i++;

@@ -576,6 +580,9 @@ static int bisect_start(struct bisect_terms *terms, const char **argv, int argc)
 	 */
 	write_file(git_path_bisect_start(), "%s\n", start_head.buf);
 
+	if (first_parent_only)
+		write_file(git_path_bisect_first_parent(), "\n");
+
 	if (no_checkout) {
 		if (get_oid(start_head.buf, &oid) < 0) {
 			res = error(_("invalid ref: '%s'"), start_head.buf);

index bc4241b51f..1585fcc6ad 100644
@@ -89,7 +89,7 @@ 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, int first_parent_only)
+static int count_interesting_parents(struct commit *commit, unsigned bisect_flags)
 {
 	struct commit_list *p;
 	int count;

@@ -97,7 +97,7 @@ static int count_interesting_parents(struct commit *commit, int first_parent_onl
 	for (count = 0, p = commit->parents; p; p = p->next) {
 		if (!(p->item->object.flags & UNINTERESTING))
 			count++;
-		if (first_parent_only)
+		if (bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY)
 			break;
 	}
 	return count;

@@ -137,7 +137,7 @@ static void show_list(const char *debug, int counted, int nr,
 	for (p = list; p; p = p->next) {
 		struct commit_list *pp;
 		struct commit *commit = p->item;
-		unsigned flags = commit->object.flags;
+		unsigned commit_flags = commit->object.flags;
 		enum object_type type;
 		unsigned long size;
 		char *buf = read_object_file(&commit->object.oid, &type,

@@ -146,9 +146,9 @@ static void show_list(const char *debug, int counted, int nr,
 		int subject_len;
 
 		fprintf(stderr, "%c%c%c ",
-			(flags & TREESAME) ? ' ' : 'T',
-			(flags & UNINTERESTING) ? 'U' : ' ',
-			(flags & COUNTED) ? '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

@@ -173,9 +173,9 @@ static struct commit_list *best_bisection(struct commit_list *list, int nr)
 	best = list;
 	for (p = list; p; p = p->next) {
 		int distance;
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
-		if (flags & TREESAME)
+		if (commit_flags & TREESAME)
 			continue;
 		distance = weight(p);
 		if (nr - distance < distance)

@@ -214,9 +214,9 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
 
 	for (p = list, cnt = 0; p; p = p->next) {
 		int distance;
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
-		if (flags & TREESAME)
+		if (commit_flags & TREESAME)
 			continue;
 		distance = weight(p);
 		if (nr - distance < distance)

@@ -261,7 +261,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all, int first_parent_only)
+					     unsigned bisect_flags)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -270,12 +270,12 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 	for (n = 0, p = list; p; p = p->next) {
 		struct commit *commit = p->item;
-		unsigned flags = commit->object.flags;
+		unsigned commit_flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit, first_parent_only)) {
+		switch (count_interesting_parents(commit, bisect_flags)) {
 		case 0:
-			if (!(flags & TREESAME)) {
+			if (!(commit_flags & TREESAME)) {
 				weight_set(p, 1);
 				counted++;
 				show_list("bisection 2 count one",

@@ -316,13 +316,13 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
-		if (first_parent_only)
+		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 exactly half-way? */
-		if (!find_all && halfway(p, nr))
+		if (!(bisect_flags & FIND_BISECTION_ALL) && halfway(p, nr))
 			return p;
 		counted++;
 	}

@@ -332,14 +332,14 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 	while (counted < nr) {
 		for (p = list; p; p = p->next) {
 			struct commit_list *q;
-			unsigned flags = p->item->object.flags;
+			unsigned commit_flags = p->item->object.flags;
 
 			if (0 <= weight(p))
 				continue;
 
 			for (q = p->item->parents;
 			     q;
-			     q = first_parent_only ? NULL : q->next) {
+			     q = bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))

@@ -353,7 +353,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			 * add one for p itself if p is to be counted,
 			 * otherwise inherit it from q directly.
 			 */
-			if (!(flags & TREESAME)) {
+			if (!(commit_flags & TREESAME)) {
 				weight_set(p, weight(q)+1);
 				counted++;
 				show_list("bisection 2 count one",

@@ -363,21 +363,21 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 				weight_set(p, weight(q));
 
 			/* Does it happen to be at exactly half-way? */
-			if (!find_all && halfway(p, nr))
+			if (!(bisect_flags & FIND_BISECTION_ALL) && halfway(p, nr))
 				return p;
 		}
 	}
 
 	show_list("bisection 2 counted all", counted, nr, list);
 
-	if (!find_all)
+	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, int find_all, int first_parent_only)
+		    int *all, unsigned bisect_flags)
 {
 	int nr, on_list;
 	struct commit_list *list, *p, *best, *next, *last;

@@ -393,16 +393,16 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	for (nr = on_list = 0, last = NULL, p = *commit_list;
 	     p;
 	     p = next) {
-		unsigned flags = p->item->object.flags;
+		unsigned commit_flags = p->item->object.flags;
 
 		next = p->next;
-		if (flags & UNINTERESTING) {
+		if (commit_flags & UNINTERESTING) {
 			free(p);
 			continue;
 		}
 		p->next = last;
 		last = p;
-		if (!(flags & TREESAME))
+		if (!(commit_flags & TREESAME))
 			nr++;
 		on_list++;
 	}

@@ -413,9 +413,9 @@ void find_bisection(struct commit_list **commit_list, int *reaches,
 	weights = xcalloc(on_list, sizeof(*weights));
 
 	/* Do the real work of finding bisection commit. */
-	best = do_find_bisection(list, nr, weights, find_all, first_parent_only);
+	best = do_find_bisection(list, nr, weights, bisect_flags);
 	if (best) {
-		if (!find_all) {
+		if (!(bisect_flags & FIND_BISECTION_ALL)) {
 			list->item = best->item;
 			free_commit_list(list->next);
 			best = list;

@@ -1000,23 +1000,30 @@ enum bisect_error bisect_next_all(struct repository *r, const char *prefix)
 	struct object_id *bisect_rev;
 	char *steps_msg;
 	int no_checkout = ref_exists("BISECT_HEAD");
-	int first_parent_only = file_exists(git_path_bisect_first_parent());
+	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)
 		return res;
 
 	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
-	revs.first_parent_only = first_parent_only;
+
+	revs.first_parent_only = !!(bisect_flags & FIND_BISECTION_FIRST_PARENT_ONLY);
 	revs.limited = 1;
 
 	bisect_common(&revs);
 
-	find_bisection(&revs.commits, &reaches, &all, !!skipped_revs.nr, first_parent_only);
+	find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 	revs.commits = managed_skipped(revs.commits, &tried);
 
 	if (!revs.commits) {

index 7f30b94db3..ec24ac2d7e 100644
@@ -12,7 +12,7 @@ struct repository;
  * best commit, as chosen by `find_all`.
  */
 void find_bisection(struct commit_list **list, int *reaches, int *all,
-		    int find_all, int first_parent_only);
+		    unsigned bisect_flags);
 
 struct commit_list *filter_skipped(struct commit_list *list,
 				   struct commit_list **tried,

@@ -23,6 +23,9 @@ struct commit_list *filter_skipped(struct commit_list *list,
 #define BISECT_SHOW_ALL		(1<<0)
 #define REV_LIST_QUIET		(1<<1)
 
+#define FIND_BISECTION_ALL			(1u<<0)
+#define FIND_BISECTION_FIRST_PARENT_ONLY	(1u<<1)
+
 struct rev_list_info {
 	struct rev_info *revs;
 	int flags;

index d1a14596b2..25c6c3b38d 100644
@@ -637,8 +637,15 @@ int cmd_rev_list(int argc, const char **argv, const char *prefix)
 
 	if (bisect_list) {
 		int reaches, all;
+		unsigned bisect_flags = 0;
 
-		find_bisection(&revs.commits, &reaches, &all, bisect_find_all, revs.first_parent_only);
+		if (bisect_find_all)
+			bisect_flags |= FIND_BISECTION_ALL;
+
+		if (revs.first_parent_only)
+			bisect_flags |= FIND_BISECTION_FIRST_PARENT_ONLY;
+
+		find_bisection(&revs.commits, &reaches, &all, bisect_flags);
 
 		if (bisect_show_vars)
 			return show_bisect_vars(&info, reaches, all);

index d5e830410f..a11fdb1473 100644
@@ -88,15 +88,16 @@ 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)
+static int count_interesting_parents(struct commit *commit, int first_parent_only)
 {
 	struct commit_list *p;
 	int count;
 
 	for (count = 0, p = commit->parents; p; p = p->next) {
-		if (p->item->object.flags & UNINTERESTING)
-			continue;
-		count++;
+		if (!(p->item->object.flags & UNINTERESTING))
+			count++;
+		if (first_parent_only)
+			break;
 	}
 	return count;
 }

@@ -259,7 +260,7 @@ static struct commit_list *best_bisection_sorted(struct commit_list *list, int n
  */
 static struct commit_list *do_find_bisection(struct commit_list *list,
 					     int nr, int *weights,
-					     int find_all)
+					     int find_all, int first_parent_only)
 {
 	int n, counted;
 	struct commit_list *p;

@@ -271,7 +272,7 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 		unsigned flags = commit->object.flags;
 
 		*commit_weight_at(&commit_weight, p->item) = &weights[n++];
-		switch (count_interesting_parents(commit)) {
+		switch (count_interesting_parents(commit, first_parent_only)) {
 		case 0:
 			if (!(flags & TREESAME)) {
 				weight_set(p, 1);

@@ -314,6 +315,8 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 			continue;
 		if (weight(p) != -2)
 			continue;
+		if (first_parent_only)
+			BUG("shouldn't be calling count-distance in fp mode");
 		weight_set(p, count_distance(p));
 		clear_distance(list);
 

@@ -332,7 +335,10 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
 
 			if (0 <= weight(p))
 				continue;
-			for (q = p->item->parents; q; q = q->next) {
+
+			for (q = p->item->parents;
+			     q;
+			     q = first_parent_only ? NULL : q->next) {
 				if (q->item->object.flags & UNINTERESTING)
 					continue;
 				if (0 <= weight(q))