suggestions for generating diffs through the revision list

I am try to walk the revision history for a given path and analyze the diff (as compared to its parent). What is the proper way of doing that?

I noticed a bunch of 'library' calls such as

init_revsion(&revs); setup_revisions(argc, argv, &revs, "HEAD"); prepare_revision_walk(&revs, NULL); commit = get_revision(&revs);

But what I can't find is the way to generate diffs. I see lots and lots of code to do it, but every builtin seems to do it differently. Not knowing the internals that well, I was hoping for some advice.

I stumbled upon calls like

run_diff_files run_diff_index

but I haven't seen how to use them correctly.

Any help would be appreciated.  Thanks.

Cheers, Don