Pre-commit

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

Features
- Add support for `prepare-commit-msg` hook
- 1004 PR by marcjay.

Fixes
- Fix repeated legacy `pre-commit install` on windows
- 1010 issue by AbhimanyuHK.
- 1011 PR by asottile.
- Whitespace fixup
- 1014 PR by mxr.
- Fix CI check for working pcre support
- 1015 PR by Myrheimb.

Misc.
- Switch CI from travis / appveyor to azure pipelines
- 1012 PR by asottile.

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

Fixes
- Fix cloning non-branch tag while in the fallback slow-clone strategy.
- 997 issue by jpinner.
- 998 PR by asottile.

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

Fixes
- Fix command length calculation on posix when `SC_ARG_MAX` is not defined.
- 691 issue by ushuz.
- 987 PR by asottile.

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

Features
- No longer require being in a `git` repo to run `pre-commit` `clean` / `gc` /
`sample-config`.
- 959 PR by asottile.
- Improve command line length limit detection.
- 691 issue by antonbabenko.
- 966 PR by asottile.
- Use shallow cloning when possible.
- 958 PR by DanielChabrowski.
- Add `minimum_pre_commit_version` top level key to require a new-enough
version of `pre-commit`.
- 977 PR by asottile.
- Add helpful CI-friendly message when running
`pre-commit run --all-files --show-diff-on-failure`.
- 982 PR by bnorquist.

Fixes
- Fix `try-repo` for staged untracked changes.
- 973 PR by DanielChabrowski.
- Fix rpm build by explicitly using `!/usr/bin/env python3` in hook template.
- 985 issue by tim77.
- 986 PR by tim77.
- Guard against infinite recursion when executing legacy hook script.
- 981 PR by tristan0x.

Misc
- Add test for `git.no_git_env()`
- 972 PR by javabrett.

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

Fixes
- Don't filter `GIT_SSH_COMMAND` env variable from `git` commands
- 947 issue by firba1.
- 948 PR by firba1.
- Install npm packages as if they were installed from `git`
- 943 issue by ssbarnea.
- 949 PR by asottile.
- Don't filter `GIT_EXEC_PREFIX` env variable from `git` commands
- 664 issue by revolter.
- 944 PR by minrk.

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

Fixes
- Improve performance of filename classification by 45% - 55%.
- 921 PR by asottile.
- Fix installing `go` hooks while `GOBIN` environment variable is set.
- 924 PR by ashanbrown.
- Fix crash while running `pre-commit migrate-config` / `pre-commit autoupdate`
with an empty configuration file.
- 929 issue by ardakuyumcu.
- 933 PR by jessebona.
- Require a newer virtualenv to fix metadata-based setup.cfg installs.
- 936 PR by asottile.