Recently most (if not all) BUG components moved from CVS to Subversion. Many recipes got updated to that fact and set to fetch source from new repository. But the problem is that all of them have PV = "1.0" so each change to code require manual rebuilding instead of letting BitBake to notice new version and do new build.
What I did in r7123-7125 was changing this. All recipes which fetch from http://svn.buglabs.net/ have now PV changed.
But then another problem appeared... Most of recipes use old way to specify which SVN revision to fetch. We changed that in OpenEmbedded quite a long time ago -- SRCREV variable was born. This way you can get revision in PV variable too.
Why it is so important to use SRCREV? Mostly because it shows which version was used to build package (as revision is part of package version now) and also if you change revision BitBake will know that and will build new package.