Currently spack is a bit of a bad actor as a zsh plugin, and it was my
fault. The autoload and compinit should really be handled by the user,
as was made abundantly clear when I found spack was doing completion
initialization for *all* of my plugins due to a deferred setup that was
getting messed up by it.
Making this conditional took spack load time from 1.5 seconds (with
module loading disabled) to 0.029 seconds. I can actually afford to load
spack by default with this change in.
Hopefully someday we'll do proper zsh completion support, but for now
this helps a lot.
* use zsh hist expansion in place of dirname
* only run (bash)compinit if compdef/complete missing
* add zsh compiled files to .gitignore
* move changes to .in file, because spack
87e456d59c