mercurial/lock.py

--- a/mercurial/lock.py	Tue Oct 06 15:55:50 2015 -0700
+++ b/mercurial/lock.py	Tue Oct 06 13:13:31 2015 -0700
@@ -40,7 +40,7 @@
     _host = None
 
     def __init__(self, vfs, file, timeout=-1, releasefn=None, acquirefn=None,
-                 desc=None, parentlock=None):
+                 desc=None, inheritchecker=None, parentlock=None):
         self.vfs = vfs
         self.f = file
         self.held = 0
@@ -48,6 +48,7 @@
         self.releasefn = releasefn
         self.acquirefn = acquirefn
         self.desc = desc
+        self._inheritchecker = inheritchecker
         self.parentlock = parentlock
         self._parentheld = False
         self._inherited = False
@@ -186,6 +187,8 @@
         if self._inherited:
             raise error.LockInheritanceContractViolation(
                 'inherit cannot be called while lock is already inherited')
+        if self._inheritchecker is not None:
+            self._inheritchecker()
         if self.releasefn:
             self.releasefn()
         if self._parentheld: