Would something like this be useful?
--- develop.html.~1.114.~ 2011-03-26 10:44:52.000000000 +0100 +++ develop.html 2011-03-26 10:58:49.311173994 +0100 @@ -434,13 +434,13 @@ | GCC 4.5.1 release (2010-07-31) GCC 4.6 Stage 3 (starts 2010-11-03) \ | v - | GCC 4.5.2 release (2010-12-16) + | r167945 GCC 4.5.2 release (2010-12-16) | +-- GCC 4.6 branch created ------+ - | \ + | r170934 \ v v GCC 4.7 Stage 1 (starts 2011-03-14) GCC 4.6.0 release (2011-03-25) - | + | r171512 | v The idea is to include the copy-source revision on the trunk or the respective branch, so that you can use the timeline to check whether a particular change came before or after a release. Of course, this is just an approximation, but it think it might still be useful.