Options like --sub-file are aliases for list actions like
--sub-files-append, which --list-options shows without a type, so
nothing was completed after them. Follow aliases to their target, and
complete typeless list actions like the list option they act on.
This makes --sub-file=, --audio-file=, --glsl-shader=, --script= etc.
complete files, --sub-files-append= etc. complete files when typed
directly, and other aliases like --fs= and --audio= complete the values
of their target.
Fixes#7955.
shbernal
9d144e57b6
