t/t5NNN: 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`. Tests that interact with submodules a handful of
times use `test_config_global` instead. Test scripts that rely on
submodules throughout use a `git config --global` during a setup test
towards the beginning of the script.

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

t/t5526-fetch-submodules.sh

@@ -35,6 +35,7 @@ add_upstream_commit() {
 }
 
 test_expect_success setup '
+	git config --global protocol.file.allow always &&
 	mkdir deepsubmodule &&
 	(
 		cd deepsubmodule &&