add --help and --verison (#73)

README.rst

@@ -37,7 +37,14 @@ Install :code:`nbqa` with
 
 .. code-block:: bash
 
-    pip install nbqa
+    $ pip install nbqa
+
+Check your installation with
+
+.. code-block:: bash
+
+    $ nbqa --version
+    nbqa 0.1.2
 
 Quickstart
 ----------
@@ -52,10 +59,10 @@ For example, you could run:
 
 .. code-block:: bash
 
-    nbqa flake8 my_notebook.ipynb
-    nbqa black my_notebook.ipynb --check
-    nbqa mypy my_notebook.ipynb --ignore-missing-imports
-    nbqa pytest my_notebook.ipynb --doctest-modules
+    $ nbqa flake8 my_notebook.ipynb
+    $ nbqa black my_notebook.ipynb --check
+    $ nbqa mypy my_notebook.ipynb --ignore-missing-imports
+    $ nbqa pytest my_notebook.ipynb --doctest-modules
 
 You can also pass an entire directory instead of a single file, e.g. :code:`nbqa flake8 .`.
 

nbqa/__main__.py

@@ -7,16 +7,28 @@
 from pathlib import Path
 from typing import List
 
-from nbqa import put_magics_back_in, replace_magics, replace_source, save_source
+from nbqa import (
+    __version__,
+    put_magics_back_in,
+    replace_magics,
+    replace_source,
+    save_source,
+)
 
 
 def _parse_args(raw_args):
     """
     Parse command-line arguments.
     """
-    parser = argparse.ArgumentParser(description="")
-    parser.add_argument("command")
-    parser.add_argument("root_dir", default=".", nargs="?")
+    parser = argparse.ArgumentParser(
+        description="Adapter to run any code-quality tool on a Jupyter notebook.",
+        usage="nbqa <command> <notebook or directory> <flags>",
+    )
+    parser.add_argument("command", help="Command to run, e.g. `flake8`.")
+    parser.add_argument(
+        "root_dir", default=".", nargs="?", help="File or directory to run command on."
+    )
+    parser.add_argument("--version", action="version", version=f"nbQA {__version__}")
     args, kwargs = parser.parse_known_args(raw_args)
     command = args.command
     root_dir = args.root_dir