Configure the linter to only check lines of code that change for new PR's

[kperrynrel]

Right now I have a PR that is failing from a previously pushed PR pep8 error (see irradiance module in #162). This PEP8 issue is deliberate as it errors on URL text in the docstring that we want to keep. @kanderso-nrel mentioned pvlib-python overrides previous PR issues in main (that are deliberate) when making new PR's by configuring the linter to only check lines of code that changed.

[wholmgren]

flake8 deprecated the diff option. For new/young projects the recommendation is to configure the linter to fail on all errors. It's much more robust that checking the diff.

[kandersolar]

I think adding a few noqa comments is fine for now. If someday it does make sense to switch to only linting the diff (which I agree is complicated), the suggestions here are a place to start: PyCQA/flake8#1760 (comment)