Merge branch '2_git_hook' into 'master'

Add a pre-commit git hook to prevent commit of a notebook with executed cells within

Closes #2

See merge request formations/cpp/gettingstartedwithmoderncpp!7

CONTRIBUTING.md

+All contributions are welcome.
+
+# Git hook
+
+If you intend to contribute, please install first the pre-commit hook:
+
+````
+cp Scripts/pre-commit .git/hooks/pre-commit
+````
+
+This hook ensure no notebook with executed cells is committed.
+
+# Workflow
+
+The project is led through an integration manager workflow, so when you have a contribution to share, just open a merge request.
+
+The MR will be reviewed and integrated directly by one of the project managers.
\ No newline at end of file

Config/README.md

 This directory includes several utilities used in the TPs and demos...
 
-The Dockerfile here is not meant to be used directly bbut the ones for TPs and the demo about third party warnings are bbuilt upon it.
+The Dockerfile here is not meant to be used directly but the ones for TPs and the demo about third party warnings are built upon it.
 
 To build it, run:
 

Scripts/check_no_executed_cell.py

+import argparse
+import sys
+from typing import Optional
+from typing import Sequence
+
+
+def find_executed_cell(filename):
+    """Read the file and check whether there is a line with "execution_count" and a non null value."""
+    stream = open(filename, encoding="utf8", errors='ignore')
+
+    executed_cells = [line.strip("\n,\" ") for line in stream if "execution_count" in line and "null" not in line ] 
+
+    return len(executed_cells)
+
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    """First argument in command line is expected to be a list of filenames
+    
+    As the purpose of this file is to be used as a pre-commit git hook, the typical list are all the files modified by the commit in progress.
+
+    If one or more file includes a cell that has been executed, the function returns 1 and print on screen the incriminated file(s).
+    """
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='Filenames to check.')
+    args = parser.parse_args(argv)
+
+    filenames_with_executed_cells = []
+
+    for filename in args.filenames:
+        if find_executed_cell(filename):
+            filenames_with_executed_cells.append(filename)
+
+    if filenames_with_executed_cells:
+        print("Commit rejected: the following files feature executed cells: \n\t- {}".format("\n\t- ".join(filenames_with_executed_cells)))
+        return 1
+    
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())
\ No newline at end of file

Scripts/pre-commit

+#!/bin/bash
+
+# This file is expected to be use as pre-commit git hook; copy it in .git/hooks/
+
+file_list=`git diff --cached --name-only`
+root_dir=`git rev-parse --show-toplevel`
+/usr/bin/env python3 ${root_dir}/Scripts/check_no_executed_cell.py ${file_list}
+