In the olden days, you would cd to your charm repository root and type jhack sync fubar to sync your files to all fubar units.
However, studies have shown that even five-characters words can be misspelled, especially when they are obscure software names, and that keyboards erode at about 2/3 of the usual rate if you type only 2/3 of the characters you usually type.
Besides, why force you to type the name of the application you want to sync to, if we can just as well grab that from the juju status?
So jhack sync has been updated to work without any arguments at all.
So long as your CWD is a folder where you have a metadata/charmcraft.yaml, jhack will match that name with the applications in your current model and default to those as your sync targets.
This update will be shipped to edge as soon as the build completes.
Have fun!