Don't rely on internals from the git completion. Instead set up the
environment and then simply call _git and let it do the completion as
it see fit.
See #292.
It's only supported as a command option and the command will fail if
-d is used as a global option. Instead of completing it in the wrong
place, don't complete it at all as it can be considered an "internal"
switch (it's not mentioned in the manual).
Erik Flodin
Tim Byrne