HG/Git: allow you to see the full diff of each commit

I cannot seem to find how to do this in SourceTree, but this is dead easy in TortoiseHG with Beyond Compare as comparison/diff tool:

See the whole diff tree of a commit (local, in the push queue, or in the pull/fetch queue) in your external diff/comparison tool.

SourceTree should make this even easier than TortoiseHG