Tests using https://sourceforge.net/p/allura/pastebin/518bb63d7929e51a2548196a/ indicate that we should be able to switch the tree browsing for git to get its info directly from GitPython without relying on the fragile index data. This should give us comparable performance without having to wait for the index to complete.
Create a GitTreeBrowser subclass to use this implementation (with tests), preferably using AJAX (tree / blob names can be pulled quickly, AJAX to fill in the rest of the last-commit data).
Done on another ticket, a while ago.