jenkinsci/jenkins — pull request #1208 by mika (2014-04-22 09:14:34+00:00)
Title: Debian postinst: check for present user/group before adding them

In git commit 7216aab0d the check for present user was removed
and therefore upgrading the Debian package on existing Jenkins
installations fails. Also the newly added code for adding a
configurable Jenkins group is missing a check for a possibly
already present Jenkins group.

Closes: JENKINS-22710