I don't know if people are aware of it.  If not, here is a simple trick to
see 'what has changed' between two versions of an executable:

ident first_executable_version second_executable_version | sort | uniq -u

For example:

ident db_purge /root/ballen/boinc/sched/db_purge  | sort | uniq -u
     $Id$
     $Id$

I find this very helpful in reviewing what has been modifed in the various
BOINC daemons, when updating versions.