Comment 4 for bug 129045

I'd suggest that this needs a new test in tests/blackbox/test_missing.py that checks that both the source and destination branches can be readonly, and that missing does not set the parent.

At the moment missing depends on the current directory. It would make the test simpler if you add a -d/--directory option to missing similar to other commands like cmd_tag. Then make two braches and use get_readonly_transport('a').base to get a url that will deny write access to them. Then try run_bzr missing between the two. Finally check that the parent was not set using branch.get_parent.