merge_tests 19 ("merge should skip over unversioned obstructions") is
one of the tests that currently fail on the tree-conflicts branch.
Discussion about this has been started in this thread:
In that thread, I claimed that the test was failing because we
were now marking obstructed files during merge as tree conflicts.
However, it looks like I didn't analyze the situation correctly
before starting that thread.
Further investigation on my part suggests that we are currently having
trouble flagging obstructed files as tree-conflict victims! The details
are still unclear to me, however. I will investigate further and once
I'm really sure I know what I'm talking about, I'll append more
information to this issue.