in_merge_bases(): support only one "other" commit

In early days of its life, I planned to make it possible to compute
"is a commit contained in all of these other commits?" with this
function, but it turned out that no caller needed it.

Just make it take two commit objects and add a comment to say what
these two functions do.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -122,7 +122,7 @@ static int branch_merged(int kind, const char *name,
 	if (!reference_rev)
 		reference_rev = head_rev;
 
-	merged = in_merge_bases(rev, &reference_rev, 1);
+	merged = in_merge_bases(rev, reference_rev);
 
 	/*
 	 * After the safety valve is fully redefined to "check with
@@ -132,7 +132,7 @@ static int branch_merged(int kind, const char *name,
 	 * a gentle reminder is in order.
 	 */
 	if ((head_rev != reference_rev) &&
-	    in_merge_bases(rev, &head_rev, 1) != merged) {
+	    in_merge_bases(rev, head_rev) != merged) {
 		if (merged)
 			warning(_("deleting branch '%s' that has been merged to\n"
 				"         '%s', but not yet merged to HEAD."),

builtin/fetch.c

@@ -314,7 +314,7 @@ static int update_local_ref(struct ref *ref,
 		return r;
 	}
 
-	if (in_merge_bases(current, &updated, 1)) {
+	if (in_merge_bases(current, updated)) {
 		char quickref[83];
 		int r;
 		strcpy(quickref, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));

commit.c

@@ -754,6 +754,9 @@ struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
 	return get_merge_bases_many(one, 1, &two, cleanup);
 }
 
+/*
+ * Is "commit" a decendant of one of the elements on the "with_commit" list?
+ */
 int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 {
 	if (!with_commit)
@@ -763,21 +766,21 @@ int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
 
 		other = with_commit->item;
 		with_commit = with_commit->next;
-		if (in_merge_bases(other, &commit, 1))
+		if (in_merge_bases(other, commit))
 			return 1;
 	}
 	return 0;
 }
 
-int in_merge_bases(struct commit *commit, struct commit **reference, int num)
+/*
+ * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
+ */
+int in_merge_bases(struct commit *commit, struct commit *reference)
 {
 	struct commit_list *bases, *b;
 	int ret = 0;
 
-	if (num == 1)
-		bases = get_merge_bases(commit, *reference, 1);
-	else
-		die("not yet");
+	bases = get_merge_bases(commit, reference, 1);
 	for (b = bases; b; b = b->next) {
 		if (!hashcmp(commit->object.sha1, b->item->object.sha1)) {
 			ret = 1;

commit.h

@@ -168,7 +168,7 @@ extern struct commit_list *get_shallow_commits(struct object_array *heads,
 		int depth, int shallow_flag, int not_shallow_flag);
 
 int is_descendant_of(struct commit *, struct commit_list *);
-int in_merge_bases(struct commit *, struct commit **, int);
+int in_merge_bases(struct commit *, struct commit *);
 
 extern int interactive_add(int argc, const char **argv, const char *prefix, int patch);
 extern int run_add_interactive(const char *revision, const char *patch_mode,

contrib/examples/builtin-fetch--tool.c

@@ -96,7 +96,7 @@ static int update_local_ref(const char *name,
 	strcpy(oldh, find_unique_abbrev(current->object.sha1, DEFAULT_ABBREV));
 	strcpy(newh, find_unique_abbrev(sha1_new, DEFAULT_ABBREV));
 
-	if (in_merge_bases(current, &updated, 1)) {
+	if (in_merge_bases(current, updated)) {
 		fprintf(stderr, "* %s: fast-forward to %s\n",
 			name, note);
 		fprintf(stderr, "  old..new: %s..%s\n", oldh, newh);

fast-import.c

@@ -1691,7 +1691,7 @@ static int update_branch(struct branch *b)
 			return error("Branch %s is missing commits.", b->name);
 		}
 
-		if (!in_merge_bases(old_cmit, &new_cmit, 1)) {
+		if (!in_merge_bases(old_cmit, new_cmit)) {
 			unlock_ref(lock);
 			warning("Not updating %s"
 				" (new tip %s does not contain %s)",

submodule.c

@@ -738,7 +738,7 @@ static int find_first_merges(struct object_array *result, const char *path,
 		die("revision walk setup failed");
 	while ((commit = get_revision(&revs)) != NULL) {
 		struct object *o = &(commit->object);
-		if (in_merge_bases(b, &commit, 1))
+		if (in_merge_bases(b, commit))
 			add_object_array(o, NULL, &merges);
 	}
 
@@ -752,7 +752,7 @@ static int find_first_merges(struct object_array *result, const char *path,
 		contains_another = 0;
 		for (j = 0; j < merges.nr; j++) {
 			struct commit *m2 = (struct commit *) merges.objects[j].item;
-			if (i != j && in_merge_bases(m2, &m1, 1)) {
+			if (i != j && in_merge_bases(m2, m1)) {
 				contains_another = 1;
 				break;
 			}
@@ -814,18 +814,18 @@ int merge_submodule(unsigned char result[20], const char *path,
 	}
 
 	/* check whether both changes are forward */
-	if (!in_merge_bases(commit_base, &commit_a, 1) ||
-	    !in_merge_bases(commit_base, &commit_b, 1)) {
+	if (!in_merge_bases(commit_base, commit_a) ||
+	    !in_merge_bases(commit_base, commit_b)) {
 		MERGE_WARNING(path, "commits don't follow merge-base");
 		return 0;
 	}
 
 	/* Case #1: a is contained in b or vice versa */
-	if (in_merge_bases(commit_a, &commit_b, 1)) {
+	if (in_merge_bases(commit_a, commit_b)) {
 		hashcpy(result, b);
 		return 1;
 	}
-	if (in_merge_bases(commit_b, &commit_a, 1)) {
+	if (in_merge_bases(commit_b, commit_a)) {
 		hashcpy(result, a);
 		return 1;
 	}