Selectively sorting directory by date in completion

Hello,

I'm posting here to share some of my configuration hoping it may be
useful to others. Also, what I've done feels pretty hacky, so if anyone
has suggestions, I'm a taker. But first, I explain my problem.

The downloads folder/directory (`~/dl` in my case) often has lots of
stuff in it but in most cases only the most recently downloaded file is
relevant. So alphabetical sort when completing file names under `~/dl`
makes no sense. There is `zstyle ':completion:*' file-sort date` which
is understood by `_path_files` to sort all file name completion by date.
I, however, find this to be undesirable for most directories other than
`~/dl` and a few others since alphabetical sort is better for scanning
with one's eyes. The global setting is too broad.

So here is the solution I came up with: I redefined `_path_files` by
symlinking `~/.local/share/zsh/site-functions/_path_files_old` to
`/usr/share/zsh/functions/Completion/Unix/_path_files` and by creating
the file `~/.local/share/zsh/site-functions/_path_files` containing

    #autoload

    case $PREFIX in
    */)
        case ${${~PREFIX:-./}:a} in
            $HOME/dl) curcontext=downloads ;;
            $HOME/tmp) curcontext=downloads ;;
            /tmp) curcontext=downloads ;;
        esac
        ;;
    esac

    _path_files_old

and adding the line

    zstyle ':completion:downloads:*' file-sort date # see our _path_files

to my `.zshrc`.

Thus far it seems to work, tough I'm uncertain about a few things:
- I'm not really sure my use of `$curcontext` is correct.
- The symlink feels kinda wrong.
- I use `${~spec}` to do filename expansion, but that also does filename
  generation. I'm not sure that's desirable.

Hope this helps someone. And again, hope to get some feedback.

Cheers,

André