[BUG] "git rebase -r" lacks sanitation on merges with arbitrary reference syntax

Hello,

I have a branch which does successive merges from a vendor branch, like:

 git merge vendor/poky-intercepts^{/warrior}'
 git merge vendor/poky-intercepts^{/zeus}'

Now if I try to use "rebase -r" across such a merge, the result is:

 error: refusing to update ref with bad name 'refs/rewritten/vendor/poky-intercepts^{/warrior}'
 hint: Could not execute the todo command
 hint: 
 hint:     label vendor/poky-intercepts^{/warrior}
 hint: 
 hint: It has been rescheduled; To edit the command before continuing, please
 hint: edit the todo list first:
 hint: 
 hint:     git rebase --edit-todo
 hint:     git rebase --continue

If I manually sanitize the label name, everything's fine.