Got it! Excellent explanation! That is the practical - this is how to reset your tree to an earlier point in time I need. I had a bunch to do today, but I will have a bit of time tomorrow to focus on this problem. I'll start at 4/4 and work backwards. I've been through each commit in the http://trinitydesktop.org/patches/ list and looking and looking at the diffs for likely ones by title (and even the unlikely ones) didn't turn up anything. It is truly a bisect and build problem. bummer ... :)
Beware that the correct method is actually to do this from within each module (tdelibs/, tdebase/, etc.): git reset --hard HEAD git checkout <hash>
Tim