Update README.md

Author: twsl

README.md

@@ -16,7 +16,7 @@ A generic python project template based on [`copier`](https://copier.readthedocs
 ## TL;DR
 
 ```bash
-copier copy --trust git+https://github.com/twsl/python-project-template path/to/destination
+copier copy --trust --vcs-ref=HEAD git+https://github.com/twsl/python-project-template path/to/destination
 ```
 
 ## Features