This is the base functionality for bash completion. Next work (in both fedpkg and rhpkg) depends on decision how should completion be activated:

• global: (triggered by # PYTHON_ARGCOMPLETE_OK line in binary)
  requires sourcing (probably in .bash_profile) of script /etc/bash_completion.d/python-argcomplete.sh. This can be performed with currently available pythonX-argcomplete packages. I do not like it much.

• specific: (preactivated by command complete -F _python_argcomplete rhpkg)
  requires script register-python-autocomplete. It is not available in some pythonX-argcomplete packages. It's OK in fc29, eng-rhel-6, eng-rhel-7 arches.
  It seems to be more reasonable for me, but some pythonX-argcomplete packages have to be prepared before.

Anyway, this PR is needed in both approaches.

Signed-off-by: Ondrej Nosek onosek@redhat.com