Features add support for hooks written in dart. #2027 PR by @asottile. add support for post-rewrite hooks. #2036 PR by @uSpike. #2035 issue by @uSpike. Fixes fix check-useless-excludes with exclude matching broken symlink. #2029 PR by @asottile. #2019 issue by @pkoch. eliminate duplicate mutable sha warning messages for pre-commit autoupdate. #2030 PR by @asottile. #2010 issue by @graingert.