commit-reach(repo_get_merge_bases_many): pass on "missing commits" errors

The `merge_bases_many()` function was just taught to indicate parsing
errors, and now the `repo_get_merge_bases_many()` function is aware of
that, too.

Naturally, there are a lot of callers that need to be adjusted now, too.

Next stop: `repo_get_merge_bases_dirty()`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

bisect.c

@@ -836,10 +836,11 @@ static void handle_skipped_merge_base(const struct object_id *mb)
 static enum bisect_error check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
 {
 	enum bisect_error res = BISECT_OK;
-	struct commit_list *result;
+	struct commit_list *result = NULL;
 
-	result = repo_get_merge_bases_many(the_repository, rev[0], rev_nr - 1,
-					   rev + 1);
+	if (repo_get_merge_bases_many(the_repository, rev[0], rev_nr - 1,
+				      rev + 1, &result) < 0)
+		exit(128);
 
 	for (; result; result = result->next) {
 		const struct object_id *mb = &result->item->object.oid;

builtin/log.c

@@ -1658,7 +1658,7 @@ static struct commit *get_base_commit(const char *base_commit,
 		struct branch *curr_branch = branch_get(NULL);
 		const char *upstream = branch_get_upstream(curr_branch, NULL);
 		if (upstream) {
-			struct commit_list *base_list;
+			struct commit_list *base_list = NULL;
 			struct commit *commit;
 			struct object_id oid;
 
@@ -1669,11 +1669,12 @@ static struct commit *get_base_commit(const char *base_commit,
 					return NULL;
 			}
 			commit = lookup_commit_or_die(&oid, "upstream base");
-			base_list = repo_get_merge_bases_many(the_repository,
+			if (repo_get_merge_bases_many(the_repository,
 						      commit, total,
-							      list);
+						      list,
+						      &base_list) < 0 ||
 			    /* There should be one and only one merge base. */
-			if (!base_list || base_list->next) {
+			    !base_list || base_list->next) {
 				if (die_on_failure) {
 					die(_("could not find exact merge base"));
 				} else {

commit-reach.c

@@ -461,17 +461,13 @@ static int get_merge_bases_many_0(struct repository *r,
 	return 0;
 }
 
-struct commit_list *repo_get_merge_bases_many(struct repository *r,
+int repo_get_merge_bases_many(struct repository *r,
 			      struct commit *one,
 			      int n,
-					      struct commit **twos)
+			      struct commit **twos,
+			      struct commit_list **result)
 {
-	struct commit_list *result = NULL;
-	if (get_merge_bases_many_0(r, one, n, twos, 1, &result) < 0) {
-		free_commit_list(result);
-		return NULL;
-	}
-	return result;
+	return get_merge_bases_many_0(r, one, n, twos, 1, result);
 }
 
 struct commit_list *repo_get_merge_bases_many_dirty(struct repository *r,

commit-reach.h

@@ -13,9 +13,10 @@ int repo_get_merge_bases(struct repository *r,
 			 struct commit *rev1,
 			 struct commit *rev2,
 			 struct commit_list **result);
-struct commit_list *repo_get_merge_bases_many(struct repository *r,
+int repo_get_merge_bases_many(struct repository *r,
 			      struct commit *one, int n,
-					      struct commit **twos);
+			      struct commit **twos,
+			      struct commit_list **result);
 /* To be used only when object flags after this call no longer matter */
 struct commit_list *repo_get_merge_bases_many_dirty(struct repository *r,
 						    struct commit *one, int n,

commit.c

@@ -1052,7 +1052,7 @@ struct commit *get_fork_point(const char *refname, struct commit *commit)
 {
 	struct object_id oid;
 	struct rev_collect revs;
-	struct commit_list *bases;
+	struct commit_list *bases = NULL;
 	int i;
 	struct commit *ret = NULL;
 	char *full_refname;
@@ -1077,8 +1077,9 @@ struct commit *get_fork_point(const char *refname, struct commit *commit)
 	for (i = 0; i < revs.nr; i++)
 		revs.commit[i]->object.flags &= ~TMP_MARK;
 
-	bases = repo_get_merge_bases_many(the_repository, commit, revs.nr,
-					  revs.commit);
+	if (repo_get_merge_bases_many(the_repository, commit, revs.nr,
+				      revs.commit, &bases) < 0)
+		exit(128);
 
 	/*
 	 * There should be one and only one merge base, when we found

t/helper/test-reach.c

@@ -115,9 +115,12 @@ int cmd__reach(int ac, const char **av)
 	else if (!strcmp(av[1], "is_descendant_of"))
 		printf("%s(A,X):%d\n", av[1], repo_is_descendant_of(r, A, X));
 	else if (!strcmp(av[1], "get_merge_bases_many")) {
-		struct commit_list *list = repo_get_merge_bases_many(the_repository,
+		struct commit_list *list = NULL;
+		if (repo_get_merge_bases_many(the_repository,
 					      A, X_nr,
-								     X_array);
+					      X_array,
+					      &list) < 0)
+			exit(128);
 		printf("%s(A,X):\n", av[1]);
 		print_sorted_commit_ids(list);
 	} else if (!strcmp(av[1], "reduce_heads")) {