Add documentation about local debug functionality.

README.md

@@ -21,6 +21,27 @@ in the `autotick-bot` subdirectory.
 If you want to stop the worker, rename the file to `please.stop` and it will not restart
 itself on the next round.
 
+
+## Debugging Locally
+You can use the CLI of the bot to debug it locally. To do so, install the bot with the following command:
+```bash
+pip install -e .
+```
+
+Then you can use the CLI like this:
+```bash
+conda-forge-tick --help
+```
+
+For debugging, use the `--debug` flag. This enables debug logging and disables multiprocessing.
+
+Note that the bot expects the [conda-forge dependency graph](https://github.com/regro/cf-graph-countyfair) to be
+present in the current working directory by default. Use `--online` to download missing files on demand from GitHub.
+
+The local debugging functionality is still work in progress and might not work for all commands.
+Currently, the following commands are supported and tested:
+- `update-upstream-versions`
+
 ## What has the bot done recently?
 
 Check out its [PRs](https://github.com/pulls?utf8=%E2%9C%93&q=is%3Aopen+is%3Apr+author%3Aregro-cf-autotick-bot+archived%3Afalse+), its currently [running jobs](https://github.com/regro/cf-scripts/actions?query=is%3Ain_progress++), and the [status page](https://conda-forge.org/status/#current_migrations)!