add pre-commit

This tool provides a extensible way to configure pre-commit hooks
to do something from running linters to spell-checking and it proved
to be useful.

Change-Id: I77cf6c85559989bd051798e601640e0039342924

.pre-commit-config.yaml

@@ -0,0 +1,27 @@
+---
+default_language_version:
+  # force all unspecified python hooks to run python3
+  python: python3
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.3.0
+    hooks:
+      - id: trailing-whitespace
+      - id: mixed-line-ending
+        args: ['--fix', 'lf']
+        exclude: '.*\.(svg)$'
+      - id: check-byte-order-marker
+      - id: check-merge-conflict
+      - id: debug-statements
+      - id: check-yaml
+        files: .*\.(yaml|yml)$
+  - repo: local
+    hooks:
+      - id: flake8
+        name: flake8
+        additional_dependencies:
+          - hacking>=3.0.1,<3.1.0
+        language: python
+        entry: flake8
+        files: '^.*\.py$'
+        exclude: '^(doc|releasenotes|tools)/.*$'

HACKING.rst

@@ -45,3 +45,18 @@ Masakari Specific Commandments
 - [M332] Yield must always be followed by a space when yielding a value.
 - [M333] Policy registration should be in the central location ``masakari/policies/``
 - [M334] Do not use the oslo_policy.policy.Enforcer.enforce() method.
+
+Use of pre-commit checks
+------------------------
+`pre-commit`_ is a software tool that allows us to manage pre-commit checks as
+part of the Git repository's configuration
+and to run checks as Git pre-commit hooks (or other types of Git hooks)
+automatically on developer machines.
+It helps to catch and fix common issues before they get pushed to the server.
+After the installation of the tool (e.g. on Fedora via
+`sudo dnf install pre-commit`) simply `cd` to the Git repository and run
+`pre-commit install` to let the tool install its Git pre-commit hook.
+From now on these predefined checks will run on files that you change in new
+Git commits.
+
+.. _pre-commit: https://pre-commit.com/