Jifty::Upgrade - Superclass for schema/data upgrades to Jifty applicaitons
Jifty::Upgrade is an abstract baseclass to use to customize schema and data upgrades that happen.
since is meant to be called by subclasses of
Calling it signifies that SUB should be run when upgrading to version VERSION,
after tables and columns are added,
but before tables and columns are removed.
If multiple subroutines are given for the same version,
they are run in order that they were set up.
Returns the list of versions that have been registered; this is called by the Jifty::Script::Schema tool to determine what to do while upgrading.
Runs the subroutine that has been registered for the given version; if no subroutine was registered, returns a no-op subroutine.
Used in upgrade subroutines, this executes the necessary SQL to rename the table, or column in the table, to a new name.