Opening Sublime Text from the command line

I nearly always open Sublime Text from the command line using subl and have specific requirements for when it should open a new window or re-use one. If I'm opening a directory, then I would like it to re-use the same window if I have previously opened that directory. However if I open a random file, I never want that file in the last directory window as it's unrelated. To do this I wrote a……