Description of problem:
The filesystem package currently owns /etc/bash_completion.d/, but that location is no longer the preferred one for packaged bash completions. The current practice is to put completions in /usr/share/bash-completion/completions, helpers in /usr/share/bash-completion/helpers, and to co-own the directories:

On an F27 system:

$ sudo dnf repoquery -f /usr/share/bash-completion|wc -l
88
$ sudo dnf repoquery -f /usr/share/bash-completion/completions|wc -l
98

(Only gstreamer1 adds a helper into /usr/share/bash-completion/helpers, and it neither owns the directory nor requires bash-completion).

It would be nicer if filesystem owned /usr/share/bash-completion{,/completions,/helpers} and the packages could rely on it.