afterlock: add the callback to the top level lock (issue4608)

If 'wlock' is taken, we should add 'afterlock' callback to the 'wlock' instead.
Otherwise, running post transaction hook after 'lock' is release but 'wlock' is
still taken lead to a deadlock (eg: 'hg update' during a hook).

This situation is much more common since: 5dc5cd7abbf5

  push: acquire local 'wlock' if "pushback" is expected (BC) (issue4596)

mercurial/localrepo.py

@@ -1194,13 +1194,16 b' class localrepository(object):'
         return l
 
     def _afterlock(self, callback):
-        """add a callback to the current repository lock.
+        """add a callback to be run when the repository is fully unlocked
 
-        The callback will be executed on lock release."""
-        l = self._lockref and self._lockref()
-        if l:
+        The callback will be executed when the outermost lock is released
+        (with wlock being higher level than 'lock')."""
+        for ref in (self._wlockref, self._lockref):
+            l = ref and ref()
+            if l and l.held:
             l.postrelease.append(callback)
-        else:
+                break
+        else: # no lock have been found.
             callback()
 
     def lock(self, wait=True):

tests/test-hook.t

@@ -1,4 +1,5 b''
 commit hooks can see env vars
+(and post-transaction one are run unlocked)
 
   $ hg init a
   $ cd a
@@ -16,6 +17,7 b' commit hooks can see env vars'
   > pretxnclose = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" pretxnclose"
   > txnclose = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" txnclose"
   > txnabort = sh -c "HG_LOCAL= HG_TAG= python \"$TESTDIR/printenv.py\" txnabort"
+  > txnclose.checklock = hg debuglock > /dev/null
   > EOF
   $ echo a > a
   $ hg add a