remote: remove the_repository from some functions

remote: remove the_repository from some functions

The remotes_remote_get_1 (and its caller, remotes_remote_get, have an
implicit dependency on the_repository due to calling
read_branches_file() and read_remotes_file(), both of which use
the_repository. The branch_get() function calls set_merge() which has an
implicit dependency on the_repository as well.

Because of this use of the_repository, the helper functions cannot be
used in code paths which operate on other repositories. A future
refactor of the submodule--helper will want to make use of some of these
functions.

Refactor to break the dependency by passing struct repository *repo
instead of struct remote_state *remote_state in a few places.

The public callers and many other helper functions still depend on
the_repository. A repo-aware function will be exposed in a following
change for git submodule--helper.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>