config: don't depend on `the_repository` with branch conditions

config: don't depend on `the_repository` with branch conditions

When computing branch "includeIf" conditions we use `the_repository` to
obtain the main ref store. We really shouldn't depend on this global
repository though, but should instead use the repository that is being
passed to us via `struct config_include_data`. Otherwise, when parsing
configuration of e.g. submodules, we may end up evaluating the condition
the via the wrong refdb.

Fix this.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>