Source Only Missing in set_action() in setup.exe

[Michael A. Chase]

ACTION_SRC_ONLY is effectively disabled because either pkg->installed or
pkg->installed->source_exists is false when set_action() is called.

I'd prefer to leave it that way and let source downloads and installs be
controlled by the "Src?" checkbox:
   For ACTION*_PREV, ACTION*_CURR, and ACTION*_TEST, the source file to use
would be the one associated with the action.
   For ACTION_UNINSTALL and ACTION_REDO, the currently installed version
would apply.
   For ACTION_SKIP, the default version would apply.

I'd like to either gray-out or not paint the "Src?" checkbox if the source
is not available, but I'm still trying to figure out how to decide.
--
Mac :})
Give a hobbit a fish and he eats fish for a day.
Give a hobbit a ring and he eats fish for an age.