How to emulate 'git stash' in fossil, bzr?

Is it possible to emulate the behavior of 'git stash' when using fossil/bzr?

Basically I'm interested in handling the following workflow:

at some point the source code tree has state X, it is commited
I proceed to writing new code, I write it for a while and I see the opportunity of a refactoring
I can't commit at this point, because the change I've started to make is not completed, it is not atomic yet
at this point I would do 'git stash', would save the current work and would get back to state X
I would do the refactoring and commit, source code now has state Y
I would merge source code in state Y with code in stash, complete the change to make it atomic, then commit once again, pushing the source code to state Z

I think that generally it is possible to emulate this scenario when using another SCM by branching the code in state X instead of doing 'git stash', doing the refactoring in that branch, then merging the branch back into the main one. But I'm aware that branching is not always a cheap operation. So are there any better particular approaches that eventually rely on specific features of fossil/bzr?

Solution

Use bzr shelve and bzr unshelve commands.