"svn head" is a moving target, it always points to the latest revision, so this is not a useful statement to determine whether or not a certain build will support it. Instead, I suggest you use of of the following notations (the actual values given are examples):
- MegaGlest 1.2.3-dev+r1234 - a build of subversion revision 1234 which carries the v1.2.3-dev version string
- MegaGlest r1234 - this will help developers, but modders will still find it difficult to tell whether or not a given build they have supports it
- MegaGlest >= 1.2.4 - the supposed - since you cannot know release versions in advance - future release version which will definitely contain this feature
I very much favor the first notation, since it is precise, and easily interpreted by many.
Nice feature by the way.