feat(ci)[commit-msg hook]: automatic check of commit message formatting

docs/How_to_contribute.md

@@ -30,6 +30,18 @@ In general it is sufficient to follow the general installation instructions. How
    - The `-e` switch ensures that changes in the python source code are immediately active.
    - `[dev]` also installs some development requirements (e.g. mypy, black, pre-commit).
  - Install some git hooks by running `pre-commit install` from the main directory of this project. These hooks help to ensure a good quality of the commited code by automatically running the black **formatter** and checking for **type safety** with mypy on every commit.
+ - Activate the git `commit-msg` hook to validate commit message formatting by creating a file named `.git/hooks/commit-msg` with the following contents:
+    ```
+    #!/bin/sh
+    python scripts/dev/check-commit-msg.py $1
+    ```
+
+## Commit messages
+Commit messages should follow the following format:
+```
+<type>(scope)[optional info]: commit message
+```
+where `<type>` can be any of `feat,fix,test,chore,wip`.
 
 ## Creating a new release
 Execute the following steps in order to create a new DiscoPoP release:

scripts/dev/check-commit-msg.py

@@ -0,0 +1,34 @@
+# This file is part of the DiscoPoP software (http://www.discopop.tu-darmstadt.de)
+#
+# Copyright (c) 2020, Technische Universitaet Darmstadt, Germany
+#
+# This software may be modified and distributed under the terms of
+# the 3-Clause BSD License.  See the LICENSE file in the package base
+# directory for details.
+
+# checks the commit message for correct formatting.
+# invoked by the git commit-msg hook, if configured.
+import sys
+import re
+
+# todo translate to python
+
+path_to_commit_msg = sys.argv[1]
+
+with open(path_to_commit_msg, "r") as f:
+    commit_msg = f.read()
+    commit_msg = commit_msg.replace("\n", "")
+
+pattern = re.compile("^(feat|fix|test|chore|wip)(\(\S+\))?(\[\S+\])?:.+$")
+matches = bool(pattern.match(commit_msg))
+
+if matches:
+    print("VALID commit message: ", commit_msg)
+    sys.exit(0)
+else:
+    print("INVALID commit message: ")
+    print("\t", commit_msg)
+    print("Please use the following format:")
+    print("\t<type>(scope)[optional info]: commit message")
+    print("where `<type>` can be any of `feat,fix,test,chore,wip`.")
+    sys.exit(1)