Refactor setup_remotes() to remove --remote overriding logic

This change simplifies the responsibilities of `setup_remotes()` by extracting
"getting the default remotes" logic to its own function and moving "--remote"
related logic to _load(). The latter, especially, helps to remove the need of
passing the "remote_url" string and "can_push?" boolean to `setup_remotes()`.
4 files changed