Improve package command, build logic

* Fix typo in README.
* Implement cloning when building, fixing all builds being dirty.
* Add --rm option to package command to remove file after publishing,
  assuming that --publish is provided.

README.md

@@ -18,10 +18,12 @@ $ composer package
 # Create package from working directory
 $ composer package --dirty
 # Create and publish without saving zipball
-$ composer package --publish gitea:myserver.tld/myowner
+$ composer package --rm --publish gitea:myserver.tld
+# Create and publish to another owner
+$ composer package --publish gitea:myserver.tld:myowner
 
 # Publish latest zipball
-$ composer package:publish gitea:myserver.tld/myowner
+$ composer package:publish gitea:myserver.tld:myowner
 ```
 
 ## Notes