t/t6NNN: allow local submodules

To prepare for the default value of `protocol.file.allow` to change to
"user", ensure tests that rely on local submodules can initialize them
over the file protocol.

Tests that only need to interact with submodules in a limited capacity
have individual Git commands annotated with the appropriate
configuration via `-c`.

Signed-off-by: Taylor Blau <me@ttaylorr.com>

t/t6008-rev-list-submodule.sh

@@ -23,7 +23,7 @@ test_expect_success 'setup' '
 
 	: > super-file &&
 	git add super-file &&
-	git submodule add "$(pwd)" sub &&
+	git -c protocol.file.allow=always submodule add "$(pwd)" sub &&
 	git symbolic-ref HEAD refs/heads/super &&
 	test_tick &&
 	git commit -m super-initial &&

t/t6134-pathspec-in-submodule.sh

@@ -9,7 +9,7 @@ test_expect_success 'setup a submodule' '
 	: >pretzel/a &&
 	git -C pretzel add a &&
 	git -C pretzel commit -m "add a file" -- a &&
-	git submodule add ./pretzel sub &&
+	git -c protocol.file.allow=always submodule add ./pretzel sub &&
 	git commit -a -m "add submodule" &&
 	git submodule deinit --all
 '