diff --git a/knowledge base/python.md b/knowledge base/python.md
index 7863086..2605459 100644
--- a/knowledge base/python.md	
+++ b/knowledge base/python.md	
@@ -6,6 +6,7 @@
 1. [Dictionaries](#dictionaries)
 1. [F-strings](#f-strings)
 1. [Logging](#logging)
+1. [CLI helpers](#cli-helpers)
 1. [Web servers](#web-servers)
    1. [Flask](#flask)
    1. [WSGI server](#wsgi-server)
@@ -17,7 +18,12 @@
 ## TL;DR
 
 ```py
-# Declare a dictionary.
+# Declare tuples.
+# If only 1 element, it requires the ending ','.
+(1, 'string')
+('element',)
+
+# Declare dictionaries.
 {'spam': 2, 'ham': 1, 'eggs': 3}
 dict(spam=2,ham=1,eggs=3)
 dict([('spam',2),('ham',1),('eggs',3)])
@@ -28,13 +34,14 @@ F"{name.lower()} is funny."
 
 # Make elements in a list unique.
 # Keep the resulting list mutable.
+# Sorts the elements (it is a set "feature").
 unique_elements = list(set(redundant_elements))
 ```
 
 ## Dictionaries
 
 ```py
-# Declare a dictionary.
+# Declare dictionaries.
 d = {'spam': 2, 'ham': 1, 'eggs': 3}
 d = dict(spam=2,ham=1,eggs=3)
 d = dict([('spam',2),('ham',1),('eggs',3)])
@@ -42,13 +49,13 @@ d = {x: x for x in range(5)}
 d = {c.lower(): c + '!' for c in ['SPAM','EGGS','HAM']}
 d = dict.fromkeys('abc',0)
 
-# Change an element.
+# Change elements.
 d['ham'] = ['grill', 'bake', 'fry']
 
-# Add a new element.
+# Add new elements.
 d['brunch'] = 'bacon'
 
-# Delete an element.
+# Delete elements.
 del d['eggs']
 d.pop('eggs')
 
@@ -96,6 +103,26 @@ logging.log(level, "{level} level message")
 
 See [logging howto] and [logging library] for more information.
 
+## CLI helpers
+
+See [click]:
+
+```py
+import click
+
+@click.command()
+@click.option('--count', default=1, help='Number of greetings.')
+@click.option('--name', prompt='Your name',
+              help='The person to greet.')
+def hello(count, name):
+    """Simple program that greets NAME for a total of COUNT times."""
+    for x in range(count):
+        click.echo(f"Hello {name}!")
+
+if __name__ == '__main__':
+    hello()
+```
+
 ## Web servers
 
 ### Flask
@@ -205,6 +232,7 @@ All the references in the [further readings] section, plus the following:
 - [10 python one-liners for dictionaries]
 - [Logging library]
 - [Subprocess library]
+- [Click]
 
 <!--
   References
@@ -228,6 +256,7 @@ All the references in the [further readings] section, plus the following:
 [*args and **kwargs in python]: https://www.geeksforgeeks.org/args-kwargs-python/
 [10 Python One-Liners for Dictionaries]: https://medium.com/codex/10-python-one-liners-for-dictionaries-d58754386a1d
 [an intro to threading in python]: https://realpython.com/intro-to-python-threading/
+[click]: https://click.palletsprojects.com/en/
 [data types]: https://www.w3schools.com/python/python_datatypes.asp
 [f-strings]: https://realpython.com/python-f-strings/
 [flask at first run: do not use the development server in a production environment]: https://stackoverflow.com/questions/51025893/flask-at-first-run-do-not-use-the-development-server-in-a-production-environmen#54381386
diff --git a/scripts/git-all.py b/scripts/git-all.py
index aebb3a6..e746921 100755
--- a/scripts/git-all.py
+++ b/scripts/git-all.py
@@ -3,25 +3,21 @@
 # Easy, quick & dirty solution to act upon multiple git repositories at once.
 
 # TODO:
-#   - proper commands
-#   - use 'gitpython' instead of calling `git`
+#   - use 'gitpython' instead of calling `git`?
 
+import click
 import logging
 import subprocess
 
 from concurrent.futures import ThreadPoolExecutor
 from os import cpu_count, getcwd, walk
-from os.path import basename, dirname, isdir
-from sys import argv
+from os.path import basename, dirname
 
-dry_run = False
-log_level = logging.WARNING
-root_directory = getcwd()
 threads_count = cpu_count()
 
-logging.basicConfig(level=log_level)
+logging.basicConfig(level=logging.WARNING)
 
-def git_command(directory, *args):
+def git_command(directory, dry_run = False, *args):
     logging.debug(f"thread for {directory}")
     logging.debug(f"using args {args}")
 
@@ -36,36 +32,48 @@ def git_command(directory, *args):
     if dry_run is False:
         subprocess.call(command)
 
-if __name__ == "__main__":
-    if "--debug" in argv:
-        logging.basicConfig(level=logging.DEBUG, force=True)
-        logging.warning("debug mode")
-        argv.remove("--debug")
+@click.command()
+@click.option('--debug', '-d', is_flag=True, default=False, help='Enable debug mode.')
+@click.option('--dry-run', '-n', is_flag=True, default=False, help='Simulate actions.')
+@click.argument('action')
+@click.argument('root_directories', type=click.Path(exists=True, file_okay=False, resolve_path=True), nargs=-1)
+def main(action, debug, dry_run, root_directories):
+    """
+    Executes the Git action on all repositories found in the ROOT_DIRECTORIES.
 
-    if "--dry-run" in argv:
-        dry_run = True
-        logging.warning("dry-run mode")
-        argv.remove("--dry-run")
+    ACTION            The git action to execute. Quoted if given with arguments.
+    ROOT_DIRECTORIES  The directories to walk while looking for repositories.
+    """
+
+    action = tuple(action.split(" "))
+    if len(root_directories) <= 0:
+        root_directories = (getcwd(),)
+
+    if debug:
+        logging.basicConfig(level=logging.DEBUG, force=True)
+        logging.warning("debug mode enabled")
+    if dry_run:
+        logging.warning("dry-run mode enabled")
 
     logging.debug(f"using globals {globals()}")
     logging.debug(f"using locals {locals()}")
 
-    logging.debug(f"using cli args {argv[1:]}")
+    repositories = []
+    for directory in root_directories:
+        logging.debug(f"starting from '{directory}'")
 
-    if isdir(argv[-1]):
-        root_directory = argv[-1]
-        git_args = argv[1:-1]
-    else:
-        git_args = argv[1:]
+        repositories_in_dir = set(dirname(dirpath) for dirpath, _, _ in walk(directory) if basename(dirpath) == '.git')
+        logging.debug(f"{directory} has repositories {', '.join(repositories_in_dir)}")
 
-    logging.debug(f"starting from {root_directory}")
-    logging.debug(f"using git args {git_args}")
-
-    repositories = set([dirname(dirpath) for dirpath, _, _ in walk(root_directory) if basename(dirpath) == ".git"])
-    logging.debug(f"found repositories {repositories}")
+        repositories.extend(repositories_in_dir)
+    repositories = set(repositories)
+    logging.debug(f"found repositories {', '.join(repositories)}")
 
     logging.debug(f"creating threads")
     with ThreadPoolExecutor(max_workers=threads_count) as executor:
         for repository in repositories:
             logging.debug(f"submitting thread for {repository}")
-            executor.submit(git_command, repository, *git_args)
+            executor.submit(git_command, repository, dry_run, *action)
+
+if __name__ == "__main__":
+    main()