Add pre-commit hooks

This ensures a few things are correct before we commit and/or push,
making life a bit easier for both our contributors and our maintainers
since some things should no longer end up in the MRs.

Activate via:
$ pre-commit install
$ pre-commit install --hook-type pre-push

The latter is required for the ci-templates hooks which are pre-push
only.

.pre-commit-config.yaml

@@ -0,0 +1,23 @@
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v2.3.0
+  hooks:
+  - id: end-of-file-fixer
+  - id: trailing-whitespace
+  - id: no-commit-to-branch
+    args: ['--branch', 'main']
+- repo: https://github.com/psf/black
+  rev: 22.10.0
+  hooks:
+  - id: black
+    args: ['--check', '--diff', '.']
+- repo: https://github.com/charliermarsh/ruff-pre-commit
+  rev: v0.0.254
+  hooks:
+  - id: ruff
+    args: ['--ignore=E741,E501', '.']
+- repo: https://gitlab.freedesktop.org/freedesktop/ci-templates.git
+  rev: 7402203527f61d6473d55ad701172d1606508c52
+  hooks:
+  - id: check-commits
+  - id: generate-template

doc/user/contributing.rst

@@ -79,6 +79,15 @@ You can omit the last step if you only want to test locally.
 Working on the code
 ------------------------------------------------------------------------------
 
+If you are planning to send patches, it's a good idea to set up
+`pre-commit <https://pre-commit.com/>`_ with these commands::
+
+     $> pre-commit install
+     $> pre-commit install --hook-type pre-push
+
+This will check a few things before you commit and/or push to your repos to
+reduce the turnaround time for some common mistakes.
+
 libinput has a roughly three-parts architecture:
 
 -  the front-end code which handles the ``libinput_some_function()`` API calls in ``libinput.c``