[RFC] bug in write lock?

[Jan Balster]

Hi all,

yesterday I noticed a strange behavior of one of my scripts, which accesses a 
bzr branch locally. The reason was that at the same time the branch was being 
updated (a push) over sftp and both (script and sftp transport) could acquire a 
write lock. After reading the code and some experiments I wrote this test:

=== modified file 'bzrlib/tests/test_sftp_transport.py'
--- bzrlib/tests/test_sftp_transport.py 2006-07-31 23:04:57 +0000
+++ bzrlib/tests/test_sftp_transport.py 2006-08-03 09:53:38 +0000
@@ -90,6 +90,24 @@
          t2 = self.get_transport()
          self.assertEquals(self.get_server().logs, [])

+    def test_compatibility_with_localtransport_lock(self):
+        from bzrlib.errors import LockError
+        b = self.make_branch('', format=bzrdir.BzrDirFormat6())
+        b = bzrlib.branch.Branch.open(self.get_url())
+
+        self.failIf(lexists('.bzr/branch-lock.write-lock'))
+        b.lock_write()
+        self.failUnlessExists('.bzr/branch-lock.write-lock')
+
+        # now access the branch locally
+        homedir = self.get_server()._homedir
+        local_branch = bzrlib.branch.Branch.open(homedir)
+        self.assertRaises(LockError, local_branch.lock_write)
+        local_branch.unlock()
+
+        b.unlock()
+        self.failIf(lexists('.bzr/branch-lock.write-lock'))
+

My question now is, is this behavior expected or is it a bug?
And if it's a feature how can i tell a script to wait until the branch is updated?

Jan