I know it's been a while (life distracted me away from this project :| ) but I am now trying to revive the development a little bit. Therefore:
Thanks for the patch!
If you are still around and can still remember your idea, I would like to understand the problem that your patch solves: the abbrev_prompt() function is used exclusively by the prompt afaik, and cd-ing to a UNC path doesn't work anyway due to a limitation in cmd.exe (I am actively looking for a workaround, but this is a different story).
FYI, your patch still applies (!) against today's pycmd_public.py -- this is pleasantly surprising, and sad at the same time (gives us an idea about the lack of activity in the code).
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Fix for issue reported
I know it's been a while (life distracted me away from this project :| ) but I am now trying to revive the development a little bit. Therefore: