You can use tla to create a new branch, either because you're forking a project, or, in my case, because I want to create a new version.
Suppose I've got revision wiclear--dj--0.3--patch-22, that is, the 22th patch in the branch 0.3 and I want to create a 0.4 branch from it.
I will issue the following commands :
tla archive-setup wiclear--dj--0.4 tla tag david.jobet@free.fr--2004-wiclear/wiclear--dj--0.3--patch-22 wiclear--dj--0.4