rebase: migrate to context manager for changing dirstate parents

hgext/rebase.py

@@ -427,9 +427,8 b' class rebaseruntime(object):'
                         mergemod.mergestate.clean(repo)
                 else:
                     # Skip commit if we are collapsing
-                    repo.dirstate.beginparentchange()
-                    repo.setparents(repo[p1].node())
-                    repo.dirstate.endparentchange()
+                    with repo.dirstate.parentchange():
+                        repo.setparents(repo[p1].node())
                     newnode = None
                 # Update the state
                 if newnode is not None: