configure.ac: Use standard --with-bash-completion-dir option

[thesamesam]

Rationale:
This makes it a lot easier to enable/disable installation
of bash completion files rather than it being based on
a certain package being installed (or not). It's useful
in Gentoo Linux for example where we may want to always
install Bash completion files to the right location, even
if the user isn't using it yet, to save rebuilds.

This makes a few changes to the current Bash completion logic, mainly:

• Falls back gracefully to a standard directory if bash-completion
  itself is not installed (in that case, we can't ask it via pkgconfig
  where to place files).

• So the behaviour is now:

  • no argument / --with-bash-completion-dir=yes:

    Asks pkgconfig, but falls back to standard directory.

  • --with-bash-completion-dir=dir:

    Use the given directory with no detection.

  • --without-bash-completion-dir:

    No installation of Bash completion files.

Signed-off-by: Sam James sam@gentoo.org

[thesamesam]

ping

[mattst88]

Cc: @stellarhopper

Please don't ignore pull requests.

[stellarhopper]

@thesamesam @mattst88 Sorry I missed this. The change makes sense - I'll pull it in manually (for signoff reasons) and queue it for v73. Thank you.

[mattst88]

Thanks!

[thesamesam]

1. Thank you!
2. Added sign off (sorry, normally I do it by default)

[stellarhopper]

@thesamesam Actually I think the meson conversion series @djbw just posted [1] a new version of already implements your proposed behavior, and that is destined for v73. I think we can simply move to the meson conversion, but I'd appreciate if you took a moment to verify that works for you. Thanks!

[thesamesam]

@stellarhopper Thank you! Not runtime tested but by eye, that does exactly what I was hoping/expecting it to. I'll close this PR and let you know if there's any trouble once the Meson port lands 😉.

Thanks again.