Updated 'Customise Kedro CLI' (#10)

docs/13_custom-datasets.md

@@ -147,4 +147,4 @@ context.catalog.load('shuttles').head()
 Kedro users create many custom dataset implementations while working on real-world projects, and it makes sense that they should be able to share their work with each other. Sharing your custom datasets implementations is possibly the easiest way to contribute back to Kedro and if you are interested in doing so, you can check out the [Kedro contribution guide](https://github.com/quantumblacklabs/kedro/blob/develop/CONTRIBUTING.md) in the GitHub.
 
 ### Next section
-[Go to the next section](./14_extending-kedro.md)
+[Go to the next section](./14_custom-cli-commands.md)

docs/14_custom-cli-commands.md

@@ -0,0 +1,44 @@
+# How to add a custom CLI command
+
+As the following steps explain, to add a new custom CLI command, you need to create a new `click` group, add a `@cli.command()` to that group and then register the new group with `cli` group defined in `src/<package_name>/cli.py`:
+
+```python
+# src/<package_name>/cli.py
+...
+
+@click.group()
+def custom():
+    """Custom commands."""
+
+@custom.command()
+def to_json():
+    """ Display the pipeline in JSON format """
+    package_name = str(Path(__file__).resolve().parent.name)
+    with KedroSession.create(package_name) as session:
+        context = session.load_context()
+        print(context.pipeline.to_json())
+
+...
+cli.add_command(jupyter_group)
+cli.add_command(custom)
+...
+```
+
+Once you have made the modification, if you run `kedro -h` in your terminal, you see the new `custom` group.
+
+![](../img/custom_command.png)
+
+Run the custom command:
+
+```shell
+$ kedro custom to-json
+```
+
+# Customise existing Kedro CLI
+
+> Note: All the existing Kedro CLI commands are closed for modification.
+
+The only possible way to extend an existing command is to create a new custom command as described in the previous section.
+
+### Next section
+[Go to the next section](./15_plugins.md)