Add check_phase to pre-commit settings

[joedevivo]

The existing behavior of pre-commit-hooks.nix is to use the pre-commit phase of pre-commit hooks, unless your default_phases = [ "manual" ]. On further inspection I found that it has to be only manual. If default_phases = [ "manual" "push" ], it will use commit. In my particular case, I wanted default_phases = [ "push" ], which then ran commit hooks when I ran nix flake check.

This PR adds check_phase to the configuration. Setting check_phase = "push" runs the pre-push phase checks when I run nix flake check no matter what my default_phases are.

[sandydoo]

On further inspection I found that it has to be only manual. If default_phases = [ "manual" "push" ], it will use commit. In my particular case, I wanted default_phases = [ "push" ], which then ran commit hooks when I ran nix flake check.

@joedevivo, if I understand correctly, the issue you were having was that, after setting default_phases = ["manual" "push"], the pre-commit hooks still ran before each commit. Is that correct?
This sounds like a bug, which might be fixed #423.

As far as the feature itself goes, the manual stage/phase we had before feels like the appropriate choice for nix flake check. Even if we expose this option (and I'm not entirely sure what the use-case for that would be), the default should remain manual.

[m1-s]

Added the mentioned test cases to the new test suite https://github.com/cachix/git-hooks.nix/pull/423/files#diff-6c8d597050bd88f356507ec90b216be2fcd69fce6e488c62060f12bae96deddeR37-R51

Indeed my PR appears to fix the mentioned issue already. Let me know if I misunderstood anything.