I think the answer that you are looking for is RCS. RCS is a form of revision control in the same vein as CVS that allows for a programmer to keep multiple revisions of a file they are working on. RCS allows you to keep a log of the various revisions you've created as well as perform diffs between revisions, number them according to development and many other features that are very conducive to keeping your programming project into perspective.

There is an excellent book on the subject, but gets pretty in depth and complicated. If you're just looking to get some of the basics in, you can check out this tutorial.

For the 2 minute answer to your question. RCS supports a couple different informational 'tags' that you can add within your code which expand to a larger piece of text. By adding $Id:$ to your file being held by RCS, the tag expands to the larger piece of information that you have in your example.

humbly -c