diff -r ced66295ea90 -r e9901d01d135 mercurial/changelog.py
--- a/mercurial/changelog.py	Tue Feb 23 22:58:30 2021 -0800
+++ b/mercurial/changelog.py	Wed Feb 03 16:33:10 2021 -0800
@@ -380,7 +380,7 @@
 
 
 class changelog(revlog.revlog):
-    def __init__(self, opener, trypending=False):
+    def __init__(self, opener, trypending=False, concurrencychecker=None):
         """Load a changelog revlog using an opener.
 
         If ``trypending`` is true, we attempt to load the index from a
@@ -389,6 +389,9 @@
         revision) data for a transaction that hasn't been finalized yet.
         It exists in a separate file to facilitate readers (such as
         hooks processes) accessing data before a transaction is finalized.
+
+        ``concurrencychecker`` will be passed to the revlog init function, see
+        the documentation there.
         """
         if trypending and opener.exists(b'00changelog.i.a'):
             indexfile = b'00changelog.i.a'
@@ -404,6 +407,7 @@
             checkambig=True,
             mmaplargeindex=True,
             persistentnodemap=opener.options.get(b'persistent-nodemap', False),
+            concurrencychecker=concurrencychecker,
         )
 
         if self._initempty and (self.version & 0xFFFF == revlog.REVLOGV1):