2.6.1: add `sink --{above,below}` bash-completion?

[lkraav]

Bash completion script has a stub implementation for -T (and --above):

--above|-T)
    :
    return;;

: is a no-op that returns empty completions. Compare this with how --color is properly implemented:

--color)
    mapfile -t COMPREPLY < <(compgen -W "auto always ansi never" -- "$cur")
    return;;

Fix: -T/--above should complete with patch names. Looking at the logic, it should use the same _patch_range function that positional arguments use. Here's what it should be:

--below|--to|-t|--above|-T)
    _patch_range "$(_visible_patches)"
    return;;

AFAICT agent got it right, and monkey-patching this into /usr/share/bash-completion/completions/stg makes sink target completion work as I would expect.

Is there some subtle non-obvious reason this has been implemented as no-op thus far? Perhaps we could patch it in now?