better rake db:migrate

I have been using a schell script so I don’t need to remember the long version number associated with ruby migrations.

#given a migration task, return the version
#e.g.: rake db:migrate:redo VERSION=$(mver create_photo)
function mver() {
  scr=${1:?Please specify migration action}
  ls db/migrate/*${scr}* | sed 's=^[^0-9]*\([0-9][^_]*\)_.*$=\1='
}
which will run migration 20100302214328_create_photos_and_folders.rb