i'd just put all the branches (main and sub ones) into the same directory (whatever the name) and put the nonbranches somewhere else.
Is it "7.<odd>" subtrees you refer to as nonbranches?
I think the semantics we wanted to achieve with nuking our old 7.<odd> repositories is to kill off all development commits to maintain only one devel tree while having that one named 7.<odd>, and living side by side with the other trees for purposes of old habit and comfort.
In a subversion based Pike repository, that would probably have been achieved through renaming a 7.<odd> tree 7.<odd+2>, retaining history while not cluttering up the Pike/ directory. Is that hard / impossible in git, or is there other reasoning behind putting devel elsewhere?
Is it the subversion tree you are trying to engit, or are you still struggling with the very seriously bloodlet history of the cvs tree? (Doing a good job of the latter is a _very_ daunting struggle, and it is likely hard to do a better or even nearly as good a job than was already done for the svn tree.)