GitLab

* Create GitHub Action for pylint script.

* Fix indent

* Add back incremental flag from TF, remove allowlist.

Running a full-repo pylint with Github Actions CI takes >40 minutes,
too long for use on presubmit.

Allowlist is per-file, so the TF allowlist offers nothing here.

* Fetch master so our script has something to diff against.

* Checkout as branch rather than as merge.

This should (?) get us only our modified files.

* Diff to common ancestor.

* Terrible no-good commit introducing linter error.

* Point to locally fetched master.

* debug logging

* HEAD missing?

* Fetch full branches.

* Fetch master again.

* Revert "debug logging"

This reverts commit 6edde819537a162a2fe4010b0e66c82b088ea7a9.

* Revert "Terrible no-good commit introducing linter error."

This reverts commit ac41b830342a21a1711a9d77a11777276602fb96.

Move to .github

TensorFlow uses a subset of pylint functionality. Script will download the latest pylint rules from the main repo at runtime.

Requires `python3.8 -m pip install pylint==2.4.4`.
This will eventually be run on-PR in this repo, but first we'll have to fix the ~900 existing violations.
Script should be usable manually for now -- call it from within a subdirectory to avoid processing the entire repo.