Fix file-changed-to-dir and dir-to-file commits (issue660).
Allow adding to dirstate files that clash with previously existing
but marked for removal. Protect from reintroducing clashes by revert.
This change doesn't address related issues with update. Current
workaround is to do "clean" update by manually removing conflicting
files/dirs from working directory.
foo renamed from bar:26d3ca0dfd18e44d796b564e38dd173c9668d3a9
rev offset length base linkrev nodeid p1 p2
0 0 6 0 0 26d3ca0dfd18 000000000000 000000000000
1 6 7 1 1 d267bddd54f7 26d3ca0dfd18 000000000000