Copyright hook gets the last commit year wrong on some files that are not touched

Closes #3

See merge request !1

Ignore protect-first-parent rule if parent not in history at all

Closes #1

See merge request !3

Pre-push hooks should run on refs pushed, not checked-out head

Closes #2

See merge request !2

A regular expression failed to match a final line of commit log output
so any file that was added in the initial commit and subsequently never
updated ended up with the wrong copyright year.

Change 'types' (AND) to 'types_or' (OR) so that the target files are
not an impossible supertype of *all* scripts and template types!

Pylint is now producing too many false positives and very little that
is not caught by flake8 or mypy.

It finally is limited to *any* file that has changed since the last
commit.

It's unlikely to every have come up, but I'm just being thorough.