Allow cloning an empty repository

Cloning an empty repository manually (that is, doing 'git init' and
then doing all configuration by hand) can be a lot of work. Save the
user this work by allowing the cloning of empty repositories.
Signed-off-by: NSverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-clone.c

@@ -522,14 +522,23 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 					     option_upload_pack);
 
 		refs = transport_get_remote_refs(transport);
-		transport_fetch_refs(transport, refs);
+		if(refs)
+			transport_fetch_refs(transport, refs);
 	}
 
-	clear_extra_refs();
+	if (refs) {
+		clear_extra_refs();
 
-	mapped_refs = write_remote_refs(refs, &refspec, reflog_msg.buf);
+		mapped_refs = write_remote_refs(refs, &refspec, reflog_msg.buf);
 
-	head_points_at = locate_head(refs, mapped_refs, &remote_head);
+		head_points_at = locate_head(refs, mapped_refs, &remote_head);
+	}
+	else {
+		warning("You appear to have cloned an empty repository.");
+		head_points_at = NULL;
+		remote_head = NULL;
+		option_no_checkout = 1;
+	}
 
 	if (head_points_at) {
 		/* Local default branch link */

t/t5701-clone-local.sh

@@ -116,4 +116,20 @@ test_expect_success 'bundle clone with nonexistent HEAD' '
 	test ! -e .git/refs/heads/master
 '
 
+test_expect_success 'clone empty repository' '
+	cd "$D" &&
+	mkdir empty &&
+	(cd empty && git init) &&
+	git clone empty empty-clone &&
+	test_tick &&
+	(cd empty-clone
+	 echo "content" >> foo &&
+	 git add foo &&
+	 git commit -m "Initial commit" &&
+	 git push origin master &&
+	 expected=$(git rev-parse master) &&
+	 actual=$(git --git-dir=../empty/.git rev-parse master) &&
+	 test $actual = $expected)
+'
+
 test_done