In webkitgtk+ we are using jhbuild to manage our build dependencies for our buildbot builders. I hit an issue where jhbuild wasn't being able to use a newer git revision for soup. The problem seems to be that although it sets the URL for the origin it never fetches, so the new hash is not there when it tries to checkout:

*** Checking out libsoup *** [14/15]
git remote set-url origin git://git.gnome.org/libsoup
git checkout 06afcdb9479b9f48f22f42198396ed5ceebcae5a
fatal: reference is not a tree: 06afcdb9479b9f48f22f42198396ed5ceebcae5a