RCS - Simple Version Control

RCS is a great simple version control. No need to create repositories. Just use it in place!  Create the file, then just check it in (creates initial archived version-controlled file: filename,v). Then just check it out again to do editing.

Check in:      $ ci -u inetd.conf
Check out:    $ co -l services

Common RCS operations:

RCS operation	Command line
Initial check-in of file (leaving file active in filesystem)	ci -u filename
Check out with lock	co -l filename
Check in and unlock (leaving file active in filesystem)	ci -u filename
Display version x.y of a file	co -px.y filename
Undo to version x.y (overwrites file active in filesystem with the specified revision)	co -rx.y filename
Diff file active in filesystem and last revision	rcsdiff filename
Diff versions x.y and x.z	rcsdiff -rx.y -rx.zfilename
View log of check-ins	rlog filename
Break an RCS lock held by another person on a file	rcs -u filename

Source: O'Reilly: The Five-Minute RCS Tutorial - Automating System Administration with Perl
also see: http://www.yolinux.com/TUTORIALS/LinuxTutorialRCSintro.html

BTW: think co -l  as being "locked" from use by other programmers (one edit at a time). It may not be necessary to use -u to unlock the file.