Before-commit

==================

Fixes
- proper detection for root commit during pre-push
- 503 PR by philipgian.
- 692 PR by samskiter.

==================

Features
- pre-commit now supports node hooks on windows.
- for now, requires python3 due to https://bugs.python.org/issue32539
- huge thanks to wenzowski for the tip!
- 200 issue by asottile.
- 685 PR by asottile.

Misc.
- internal reorganization of `PrefixedCommandRunner` -> `Prefix`
- 684 PR by asottile.
- https-ify links.
- pre-commit.com is now served over https.
- 688 PR by asottile.

==================

Fixes
- Fix `local` golang repositories with `additional_dependencies`.
- 679 680 issue and PR by asottile.

Misc.
- Replace some string literals with constants
- 678 PR by revolter.

==================

Fixes
- Invoke `git diff` without a pager during `--show-diff-on-failure`.
- 676 PR by asottile.

==================

Fixes
- `pre-commit` on windows can find pythons at non-hardcoded paths.
- 674 PR by asottile.

==================

Fixes
- `pre-commit` no longer clears `GIT_SSH` environment variable when cloning.
- 671 PR by rp-tanium.