This is a stab at a tool to better manage updating files in /etc after
OS upgrades via buildworld/installworld.  Specifically, it aims to minimize
the amount of user interaction required and provide an experience similar
to doing an 'svn up' on a modified source tree.

The easiest way to get started is to do the following:

1) install the files in this directory to /usr/src/usr.sbin/etcupdate

2) Run 'make install' from this directory.  This will install the script
   and the manual page.

3) Before using 'svn' or 'cvs' to update your source tree, run
   'etcupdate extract' as root to bootstrap the state.  This assumes
   that your source matches your currently installed world.  If that is
   not the case then you have to find a matching source tree and use
   'etcupdate extract -s /path/to/source/tree' or update your world to
   match your current sources (including whatever process you use now to
   update /etc).  If you have a matching world build for your source tree,
   then run 'etcupdate extract -B' instead to minimize annoying conflicts
   in /etc/mail/*.cf.

4) After your next (cvs|svn) up/buildworld/installworld cycle, run
   'etcupdate' as root when you would normally run mergemaster.

5) If it doesn't encounter any warnings or conflicts, you are done.  You
   can use 'etcupdate status' to check for any warnings or conflicts.

6) If there are conflicts you can use 'etcupdate resolve' to resolve them
   interactively akin to what happens during 'svn merge' or 'p4 resolve'.

7) If there are warnings you have to decide if they matter or not and how
   you want to cope with them.  Generally warnings happen due to obscure
   things like you changed a file in /etc to be a directory or vice versa.

8) You can use 'etcupdate diff' at anytime after step 3) to view a diff
   of your /etc against a stock version.  This will show you what local
   modifications you have made.  NB: This will _not_ include new files
   you have added to /etc such as /etc/fstab or /etc/rc.conf.  It may also
   be useful to do this right after step 3) to make sure all the local
   modifications you expect are listed.

For more details, check the etcupdate(8) man page.

This file can be found at http://www.FreeBSD.org/~jhb/etcupdate/