That variable was a leftover because I initially thought about putting this inside `vimsupport` as a general function. I forgot to take out.
For the other point: I think I need three return values: blacklisted (`-1` now), whitelisted (`1`) and not contained in glob list (`0`). The user should only need to see the confirm dialog in the last case. I could also rename the function and return `False`, `True` and `None`.
In the current implementation I'm returning truthy values if the file was matched by a pattern and falsey values if it wasn't.