A far more easy way is to have an html rendered version that comes from each branch. Sure, there's still a bit of undocumented stuff that might become documented only in a later version, but then it's just a matter of surfing to the later version while keeping in mind that there might be stuff there that doesn't apply.
The main manual available at the web site should of course be for the last released version.
/ Martin Stjernholm, Roxen IS
Previous text:
2004-05-06 22:27: Subject: Docs branching/tagging?
No, since you already suggested it. :-)
Seriously, it is a good idea. You are very welcome to implement it, if you can. Tagging it up explicitly is probably the best way of doing it (perhaps a @version autodoc keyword, i e @version 7.5.23).
/ Johan Sundström (Achtung Liebe!)