How do I quickly check what heads a particular commit is in?

In the middle of a merge of 2 of a bunch of closely related heads, I
found a few odd things, so I've pickaxe'd and found the (potentially
bogus) commits. I am using gitk, and while I do find the commit, it's
not very clear what heads have the dodgy commit. They've probably been
for a few months in there <sigh>.

Is there a practical way to ask in what heads they are?



martin