diff -r 4d780d510b44 -r 4ecc6047d45f mercurial/cmdutil.py
--- a/mercurial/cmdutil.py	Tue Jun 27 00:01:17 2017 -0700
+++ b/mercurial/cmdutil.py	Mon Jun 26 15:46:24 2017 +0200
@@ -1411,6 +1411,8 @@
             self.ui.write(_("trouble:     %s\n") % ', '.join(ctx.troubles()),
                           label='log.trouble')
 
+        self._exthook(ctx)
+
         if self.ui.debugflag:
             files = ctx.p1().status(ctx)[:3]
             for key, value in zip([# i18n: column positioning for "hg log"
@@ -1457,6 +1459,11 @@
 
         self.showpatch(ctx, matchfn)
 
+    def _exthook(self, ctx):
+        '''empty method used by extension as a hook point
+        '''
+        pass
+
     def showpatch(self, ctx, matchfn):
         if not matchfn:
             matchfn = self.matchfn