Arbitrary zsh completion using a keybinding

Question

Sometimes a command doesn't have a completion installed—or syntactically could accept a whole bunch of types of arguments, rendering completion next to useless. For instance, "git checkout" can take the name of any git-tracked file or the name of any ref or other tree-ish. It can also take some option flags. That's a lot of possible completions.

Knowing that I want to complete—say—a branch name, is there a way to bind a key to complete against or display a menu of branch names? (And likewise for any category of completion.)

That seems possible and useful, but I haven't seen it done.

Answer 1

Yes, this can be done. I originally got the following from one of the zsh mailing lists, but I don't recall who posted it:

zle -C complete-file complete-word _generic
zstyle ':completion:complete-file::::' completer _files
bindkey '^x^f' complete-file

This could be easily adapted to use a different completion function rather than _files.

The first line defines a new completion widget named complete-file which behaves like the builtin complete-word widget and uses the _generic function to generate the list of completions.

The second line then configures it so that when that custom widget is used the completer will only use _files to get the list of completions.

Then the third line binds the new widget to a key sequence.