postrm is in git-daemon-sysvinit 1:2.7.4-0ubuntu1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | #!/bin/sh
set -e
test "$1" = 'remove' || exit 0
update-rc.d git-daemon remove >/dev/null
|