diff --git a/hgext/rebase.py b/hgext/rebase.py
--- a/hgext/rebase.py
+++ b/hgext/rebase.py
@@ -821,10 +821,7 @@
         rbsrt = rebaseruntime(repo, ui, inmemory, opts)
         with repo.wlock(), repo.lock():
             try:
-                overrides = {('rebase', 'singletransaction'): True}
-                with ui.configoverride(overrides, 'rebase'):
-                    _origrebase(ui, repo, inmemory=True, rbsrt=rbsrt,
-                                leaveunfinished=True, **opts)
+                _dryrunrebase(ui, repo, rbsrt, **opts)
             except error.InMemoryMergeConflictsError:
                 ui.status(_('hit a merge conflict\n'))
                 return 1
@@ -848,6 +845,12 @@
     else:
         return _origrebase(ui, repo, **opts)
 
+def _dryrunrebase(ui, repo, rbsrt, **opts):
+    overrides = {('rebase', 'singletransaction'): True}
+    with ui.configoverride(overrides, 'rebase'):
+        return _origrebase(ui, repo, inmemory=True, rbsrt=rbsrt,
+                           leaveunfinished=True, **opts)
+
 def _origrebase(ui, repo, inmemory=False, leaveunfinished=False, rbsrt=None,
                 **opts):
     opts = pycompat.byteskwargs(opts)