diff -r 5694311db6ed -r eb84b4ad41e5 mercurial/repair.py
--- a/mercurial/repair.py	Mon Jun 19 11:21:37 2017 -0700
+++ b/mercurial/repair.py	Mon Jun 19 11:24:21 2017 -0700
@@ -76,8 +76,9 @@
     return s
 
 def strip(ui, repo, nodelist, backup=True, topic='backup'):
-    # This function operates within a transaction of its own, but does
-    # not take any lock on the repo.
+    # This function requires the caller to lock the repo, but it operates
+    # within a transaction of its own, and thus requires there to be no current
+    # transaction when it is called.
     # Simple way to maintain backwards compatibility for this
     # argument.
     if backup in ['none', 'strip']: