Use dulwich.config.ConfigFile.
Remove custom config parser - call out to standard parser in dulwich instead.
Require newer version of Dulwich.
Simplify tag_list function.
Simplify Repo.commit by calling out to Dulwich.
Remove unused _get_config_user helper.
Simplify repo.fetch.
Remove unused exceptions.
Remove unused _get_working_tree.
Simplify Repo.export.
Avoid accessing private member variable of Index when removing entries.
Remove unused functions _write_packed_refs and get_sha1_from_refspec.