pre-commit: Add configuration to check coding style on commit

Also document the usage in CONTRIBUTING.md.

Author: schodet

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+repos:
+-   repo: local
+    hooks:
+    -   id: codeformat_c
+        name: codeformat-c
+        language: system
+        entry: poetry run ./tools/codeformat.py -cf
+        types: [c]
+    -   id: codeformat_py
+        name: codeformat-py
+        language: system
+        entry: poetry run ./tools/codeformat.py -p
+        types: [python]
+        pass_filenames: false

CONTRIBUTING.md

@@ -215,6 +215,13 @@ Before committing your changes, be sure to run:
 This will automatically fix common problems in files that follow the MicroPython
 style.
 
+This can be run automatically using pre-commit. Install pre-commit, then run:
+
+    pre-commit install
+
+It will install a pre-commit hook for this repository. On every commit, the
+coding style will be checked before the commit is done.
+
 
 ### Logical commits