Install the default "master" branch configuration after cloning a void

After "cloning from an empty repository", we have a configuration to
describe the remote's URL and the default ref mappings, but we lack the
branch configuration for the default branch we create on our end,
"master".

It is likely that the empty repository we cloned from will point the
default "master" branch with its HEAD, so prepare the local configuration
to match.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-clone.c

@@ -350,6 +350,19 @@ static struct ref *write_remote_refs(const struct ref *refs,
 	return local_refs;
 }
 
+static void install_branch_config(const char *local,
+				  const char *origin,
+				  const char *remote)
+{
+	struct strbuf key = STRBUF_INIT;
+	strbuf_addf(&key, "branch.%s.remote", local);
+	git_config_set(key.buf, origin);
+	strbuf_reset(&key);
+	strbuf_addf(&key, "branch.%s.merge", local);
+	git_config_set(key.buf, remote);
+	strbuf_release(&key);
+}
+
 int cmd_clone(int argc, const char **argv, const char *prefix)
 {
 	int use_local_hardlinks = 1;
@@ -539,6 +552,9 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		head_points_at = NULL;
 		remote_head = NULL;
 		option_no_checkout = 1;
+		if (!option_bare)
+			install_branch_config("master", option_origin,
+					      "refs/heads/master");
 	}
 
 	if (head_points_at) {
@@ -567,11 +583,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 				      head_points_at->peer_ref->name,
 				      reflog_msg.buf);
 
-			strbuf_addf(&key, "branch.%s.remote", head);
-			git_config_set(key.buf, option_origin);
-			strbuf_reset(&key);
-			strbuf_addf(&key, "branch.%s.merge", head);
-			git_config_set(key.buf, head_points_at->name);
+			install_branch_config(head, option_origin,
+					      head_points_at->name);
 		}
 	} else if (remote_head) {
 		/* Source had detached HEAD pointing somewhere. */

t/t5601-clone.sh

@@ -144,4 +144,19 @@ test_expect_success 'clone to an existing path' '
 	test_must_fail git clone src target-5
 '
 
+test_expect_success 'clone a void' '
+	mkdir src-0 &&
+	(
+		cd src-0 && git init
+	) &&
+	git clone src-0 target-6 &&
+	(
+		cd src-0 && test_commit A
+	) &&
+	git clone src-0 target-7 &&
+	# There is no reason to insist they are bit-for-bit
+	# identical, but this test should suffice for now.
+	test_cmp target-6/.git/config target-7/.git/config
+'
+
 test_done