Extracting configuration related logic came up in reviews multiple times.
Also, the VS Code logic returns missing properties as null.
This behaviour is not ideal because null function arguments overrdie the
default function arguments.

Related discussions:
- https://gitlab.com/gitlab-org/gitlab-vscode-extension/-/merge_requests/115#note_432956679

This is the first step in not swallowing critical errors deep in
the GitService. It allows us to follow the error path for each
public function separately.