Merge branch 'ab/perl-python-attrs'

We learned that our source files with ".pl" and ".py" extensions are Perl and Python files respectively and changes to them are better viewed as such with appropriate diff drivers. * ab/perl-python-attrs: .gitattributes: add a diff driver for Python .gitattributes: use the "perl" differ for Perl .gitattributes: add *.pl extension for Perl