Based on https://github.com/Valodim/zsh-capture-completion
`zpty -r` with a pattern seems to have some funky behavior on older
versions, giving unpredictable results
Don't use `-s` option to `zmodload`. It is not available in zsh versions
older than 5.3
If running in sync mode and a completion takes a long time, the user can
^C out of it. We need to use `always` in the strategy function or the
pty will not be destroyed in this case and the next time we go to create
it, it will fail, making the shell unusable.
User can have many different completion styles set that will modify what
they've already typed. These styles will result in suggestions that
don't match what the user has already typed. We try our best to unset
some of the more problematic ones, but add some code to fetch to
invalidate suggestions that don't match what the user's already typed.
Eric Freese
Martin Väth