remote: drop "explicit" parameter from remote_ref_for_branch()

Commit 9700fae5ee (for-each-ref: let upstream/push report the remote
ref name, 2017-11-07) added a remote_ref_for_branch() helper, which
is modeled after remote_for_branch(). This includes providing an
"explicit" out-parameter that tells the caller whether the remote
was configured by the user, or whether we picked a default name like
"origin".

But unlike remote names, there is no default name when the user
didn't configure one.  The only way the "explicit" parameter is used
by the caller is to use the value returned from the helper when it
is set, and use an empty string otherwise, ignoring the returned
value from the helper.

Let's drop the "explicit" out-parameter, and return NULL when the
returned value from the helper should be ignored, to simplify the
function interface.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Damien Robert <damien.olivier.robert+git@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/ref-filter.c b/ref-filter.c
index 6867e33..9837700 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -1459,12 +1459,10 @@
 			remote_for_branch(branch, &explicit);
 		*s = xstrdup(explicit ? remote : "");
 	} else if (atom->u.remote_ref.option == RR_REMOTE_REF) {
-		int explicit;
 		const char *merge;
 
-		merge = remote_ref_for_branch(branch, atom->u.remote_ref.push,
-					      &explicit);
-		*s = xstrdup(explicit ? merge : "");
+		merge = remote_ref_for_branch(branch, atom->u.remote_ref.push);
+		*s = xstrdup(merge ? merge : "");
 	} else
 		BUG("unhandled RR_* enum");
 }
diff --git a/remote.c b/remote.c
index 593ce29..c43196e 100644
--- a/remote.c
+++ b/remote.c
@@ -516,14 +516,11 @@
 	return remote_for_branch(branch, explicit);
 }
 
-const char *remote_ref_for_branch(struct branch *branch, int for_push,
-				  int *explicit)
+const char *remote_ref_for_branch(struct branch *branch, int for_push)
 {
 	if (branch) {
 		if (!for_push) {
 			if (branch->merge_nr) {
-				if (explicit)
-					*explicit = 1;
 				return branch->merge_name[0];
 			}
 		} else {
@@ -534,15 +531,11 @@
 			if (remote && remote->push.nr &&
 			    (dst = apply_refspecs(&remote->push,
 						  branch->refname))) {
-				if (explicit)
-					*explicit = 1;
 				return dst;
 			}
 		}
 	}
-	if (explicit)
-		*explicit = 0;
-	return "";
+	return NULL;
 }
 
 static struct remote *remote_get_1(const char *name,
diff --git a/remote.h b/remote.h
index b134cc2..11d8719 100644
--- a/remote.h
+++ b/remote.h
@@ -261,8 +261,7 @@
 struct branch *branch_get(const char *name);
 const char *remote_for_branch(struct branch *branch, int *explicit);
 const char *pushremote_for_branch(struct branch *branch, int *explicit);
-const char *remote_ref_for_branch(struct branch *branch, int for_push,
-				  int *explicit);
+const char *remote_ref_for_branch(struct branch *branch, int for_push);
 
 /* returns true if the given branch has merge configuration given. */
 int branch_has_merge_config(struct branch *branch);