Explicitly enable extended globbing

On my netbook (main development machine for cheats), this was already
enabled, so that I never stumbled over this nasty bug: if the shell
option extglob isn’t set, the *(...) pattern isn’t enabled, and our
code to parse the prompt line won’t work, instead using the whole line
as prompt ("folder:The folder").
Add another git add cheat for the -p option

-p is similar to -i, but takes a file name, skipping -i’s file selection
menu.