up-thread should stop or combine automatically.

[Robert Collins]

195133 introduced an automatic up-thread, which is now the default. However it does not interact beautifully with the empty delta detection:

robertc@lifeless-64:~/source/baz/plugins/loom/testloom$ bzr up-thread
All changes applied successfully.
Moved to thread 'thread'.
This thread is now empty, you may wish to run "bzr combine-thread" to remove it.
Committing to: /home/robertc/source/baz/plugins/loom/testloom/
Committed revision 117.
robertc@lifeless-64:~/source/baz/plugins/loom/testloom$ bzr st
Current thread: thread

This really should either stop, or automatically discard the thread when doing this. Remembering that looms are revertable as a whole, so its not as disasterous as first glance might suggest.