Merge branch 'jk/allow-fetch-onelevel-refname' into maint

"git clone" would fail to clone from a repository that has a ref
directly under "refs/", e.g. "refs/stash", because different
validation paths do different things on such a refname.  Loosen the
client side's validation to allow such a ref.

* jk/allow-fetch-onelevel-refname:
  fetch-pack: do not filter out one-level refs

t/t5510-fetch.sh

@@ -594,4 +594,15 @@ test_expect_success 'all boundary commits are excluded' '
 	test_bundle_object_count .git/objects/pack/pack-${pack##pack	}.pack 3
 '
 
+test_expect_success 'fetching a one-level ref works' '
+	test_commit extra &&
+	git reset --hard HEAD^ &&
+	git update-ref refs/foo extra &&
+	git init one-level &&
+	(
+		cd one-level &&
+		git fetch .. HEAD refs/foo
+	)
+'
+
 test_done