clone: use git protocol for cloning shallow repo locally

clone_local() does not handle $SRC/shallow. It could be made so, but
it's simpler to use fetch-pack/upload-pack instead.

This used to be caught by the check in upload-pack, which is triggered
by transport_get_remote_refs(), even in local clone case. The check is
now gone and check_everything_connected() should catch the result
incomplete repo. But check_everything_connected() will soon be skipped
in local clone case, opening a door to corrupt repo. This patch should
close that door.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/clone.c

@@ -797,8 +797,15 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	else
 		repo = repo_name;
 	is_local = option_local != 0 && path && !is_bundle;
-	if (is_local && option_depth)
-		warning(_("--depth is ignored in local clones; use file:// instead."));
+	if (is_local) {
+		if (option_depth)
+			warning(_("--depth is ignored in local clones; use file:// instead."));
+		if (!access(mkpath("%s/shallow", path), F_OK)) {
+			if (option_local > 0)
+				warning(_("source repository is shallow, ignoring --local"));
+			is_local = 0;
+		}
+	}
 	if (option_local > 0 && !is_local)
 		warning(_("--local is ignored"));
 

t/t5601-clone.sh

@@ -340,4 +340,11 @@ test_expect_success 'clone from a repository with two identical branches' '
 
 '
 
+test_expect_success 'shallow clone locally' '
+	git clone --depth=1 --no-local src ssrrcc &&
+	git clone ssrrcc ddsstt &&
+	test_cmp ssrrcc/.git/shallow ddsstt/.git/shallow &&
+	( cd ddsstt && git fsck )
+'
+
 test_done