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.
This is more or less what happens in my svn import. At a split point, 7.<odd+1> and 7.<odd+2> are both created as copies (with history) of 7.<odd>, and 7.<odd> is deleted. This is eqivalent to a rename and a copy, but there is no distinction in which one is the copy and which one is the rename. Therefore there is no "branch" and "nonbranch" distinction between the two either.