postinst is in the 3.3~rc1-2.
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 7 8 9 10 11 | #!/bin/sh 
set -e
if [ -x /usr/bin/update-menus ] ; then 
  update-menus
fi
update-alternatives --quiet --install /usr/bin/editor editor /usr/bin/the 10\
  --slave /usr/share/man/man1/editor.1.gz editor.1.gz \
          /usr/share/man/man1/the.1.gz
 |