localrepo: add a `currentlock` method

It mirrors he `currentwlock` function.

mercurial/interfaces/repository.py

@@ -1810,6 +1810,9 b' class ilocalrepositorymain(interfaceutil'
     def lock(wait=True):
         """Lock the repository store and return a lock instance."""
 
+    def currentlock():
+        """Return the lock if it's held or None."""
+
     def wlock(wait=True):
         """Lock the non-store parts of the repository."""
 

mercurial/localrepo.py

@@ -3141,6 +3141,10 b' class localrepository:'
         """Returns the wlock if it's held, or None if it's not."""
         return self._currentlock(self._wlockref)
 
+    def currentlock(self):
+        """Returns the lock if it's held, or None if it's not."""
+        return self._currentlock(self._lockref)
+
     def checkcommitpatterns(self, wctx, match, status, fail):
         """check for commit arguments that aren't committable"""
         if match.isexact() or match.prefix():