debugrebuildstate: wrap the operation in a `changing_parents` context

This ismaybe a "changing_files" case? However this would be the only
usage of `rebuild` outside a `changing_parents` context and this is a debug
command, so lets not make the code base more complex because of that one command.

mercurial/debugcommands.py

@@ -3142,8 +3142,8 b' def debugrebuilddirstate(ui, repo, rev, '
             dsnotadded = {f for f in dsonly if not dirstate.get_entry(f).added}
             changedfiles = manifestonly | dsnotadded
 
+        with dirstate.changing_parents(repo):
         dirstate.rebuild(ctx.node(), ctx.manifest(), changedfiles)
-        dirstate.write(repo.currenttransaction())
 
 
 @command(