Branch from a branch: moving to a normal branch

[Jacob Weber <ja...@jacobweber.com>]

I normally create branches from trunk, work on them, and eventually 
reintegrate them back into trunk.

Sometimes I'll create a branch Y from another branch X, so I can start 
with X's code. Normally I'll reintegrate Y into X first, then reintegrate X 
into trunk.

Y --> X --> trunk

But what if I want to reintegrate X into trunk first, and I no longer want 
Y to depend on X? In other words, I want Y to be a normal branch, so 
that I can merge it directly to and from trunk, without going through X.

Y --> trunk
X --> trunk

What should I do? One approach would be to create a new branch, and 
merge all of Y's changes into it. But I'd like to keep using Y if possible, 
so I don't lose track of its history. Is that possible?

Jacob