diff --git a/mercurial/cext/revlog.c b/mercurial/cext/revlog.c
--- a/mercurial/cext/revlog.c
+++ b/mercurial/cext/revlog.c
@@ -16,9 +16,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "compat.h"
 #include "bitmanipulation.h"
 #include "charencode.h"
+#include "compat.h"
 #include "revlog.h"
 #include "util.h"
 
diff --git a/mercurial/interfaces/repository.py b/mercurial/interfaces/repository.py
--- a/mercurial/interfaces/repository.py
+++ b/mercurial/interfaces/repository.py
@@ -1702,6 +1702,9 @@
     def transaction(desc, report=None):
         """Open a new transaction to write to the repository."""
 
+    def new_cl_rev_callback(rev):
+        """Extension point for caches for new changelog revisions."""
+
     def undofiles():
         """Returns a list of (vfs, path) for files to undo transactions."""