Remove the default command #361
Description
What needs to get done
Remove support for the dispatcher's default command.
Why it needs to get done
A default command was added to craft-cli to maintain compatibility with Snapcraft. Default commands aren't a good UX practice and no other craft app supports them.
Snapcraft 9 dropped support for the default command, but craft-cli still needs to provide a helpful error message:
Running snapcraft without a command isn't supported.
Use 'snapcraft pack' instead.
Craft-cli can fully drop support when Snapcraft 10 (core28) is released, as this version of Snapcraft will do what the other apps do (show the help text).