Only run codechecks on changed Python source files

.pre-commit-config.yaml

@@ -1,9 +1,10 @@
 repos:
-  - repo: local
+  - repo: "local"
     hooks:
-    - id: codechecks
-      name: codechecks
+    - id: "codechecks"
+      name: "codechecks"
       stages: ["push"]
+      language: "system"
+      files: ".py$"
       entry: "tox -e codechecks"
-      language: system
-      pass_filenames: false
+      pass_filenames: true

tox.ini

@@ -95,12 +95,16 @@ setenv =
          #     .decode(getattr(sys.stdout, "encoding", "utf8"))
          # `TypeError: decode() argument 1 must be string, not None`
          PYTHONIOENCODING=utf_8
+
+	 # If no positional arguments are given, try to run the checks on the
+	 # entire codebase, including various pieces of supporting code.
+	 DEFAULT_FILES="src integration static misc setup.py"
 commands =
-         flake8 src integration static misc setup.py
-         python misc/coding_tools/check-umids.py src
-         python misc/coding_tools/check-debugging.py
-         python misc/coding_tools/find-trailing-spaces.py -r src static misc setup.py
-         python misc/coding_tools/check-miscaptures.py
+         flake8 {posargs:{env:DEFAULT_FILES}}
+         python misc/coding_tools/check-umids.py {posargs:{env:DEFAULT_FILES}}
+         python misc/coding_tools/check-debugging.py {posargs:{env:DEFAULT_FILES}}
+         python misc/coding_tools/find-trailing-spaces.py -r {posargs:{env:DEFAULT_FILES}}
+         python misc/coding_tools/check-miscaptures.py {posargs:{env:DEFAULT_FILES}}
 
          # If towncrier.check fails, you forgot to add a towncrier news
          # fragment explaining the change in this branch.  Create one at