Simple Revision Control
 
The venerable RCS (Revision Control System) has survived into the era
of distributed version control because it fills a niche: sometimes you
only *want* to track changes in single files at a time - for example,
if you have a directory full of documents with separate histories.
 
SRC (Simple Revision Control) is RCS, reloaded.  It remains
determinedly file-oriented and doesn't even track the committer of a
change (because that's always you), but incorporates the design and
user-interface lessons of modern systems.  It features sequential
revision numbers, lockless operation, embedded command help, and a
command set that will seem familiar to users of Subversion, Mercurial,
and Git.