Complete something not according to the context in zsh

Question

I use zsh with the “new” completion system (compinit). Sometimes I want to restrict completion to a subset of what is possible, to cut down on ambiguity. This is a user choice, not a configuration setting: I want to hit a different key instead of Tab to get a different set of completions. I don't want to configure completions differently for that command. Tab should still do its normal thing.

In some cases, there are workarounds. For example, I have a key bound to _bash_complete-word, which in most cases completes files. But sometimes I want a less common focus. For example:

• Complete only host names after scp, not local file names.
• Complete only remote names after git checkout, not branch names.

How can I bind a key that will complete remote names after git checkout, but not branch names? More generally, how can I bind a key to complete something different from what would normally be completed in the current context?

Answer 1

The snippet below causes Meta+r to complete git remote names when on a git command line, and host names elsewhere.

_complete-remotes () {
  case $words[1] in
    git) load_helper_functions _git; __git_remotes;;
    *) _hosts;;
  esac
}
compdef -k _complete-remotes complete-word '^[r'

• See Can I use a helper function from a ZSH completion file in another for load_helper_functions. If you remove it from the code above, it will only work if completion for git has been performed at least once before in the current zsh session.
• $words[1] is the first word of the command-with-arguments that is to be completed.
• complete -k … registers the function _complete-remotes as a completion widget (which allows it to run completion builtins) and binds it to Meta+r.