Fixed #25420 -- Documented bash completion exit code behavior.

Thanks Common Code for financing the work on this commit.

Thanks Common Code for financing the work on this commit.

Thanks Trac alias master for the report and review.

Thanks Sai Krishna for the initial patch.

Thanks David Szotten for the report and Tommy Beadle for code inspiration.
Thanks Tim Graham for the review.

Thanks Pablo Oubiña for the report.

Thanks mlissner for the suggestion.

Thanks Simon Meers for the initial patch, and Tim Graham for the review.

Thanks Claude Paroz and Tim Graham for polishing the patch.

Thanks Anssi Kääriäinen for the patch suggestion, and Tim Graham for the review.

Thanks Ian Foote for the initial patch.

Thanks Trac alias trkjgrdg for the report and Tim for investigation and review.

Thanks Tim Graham for precious inputs.

Fixed #25987 -- Made inline formset validation respect unique_together with an unsaved parent object.

Thanks Anton Kuzmichev for the report and Tim for the review.