Ok, I did something stupid.
I have forked a repo on Github. I made some changes, commited them into one commit, pushed that to my fork, and then on Github I created a pull request for the project owner (upstream).
Only, the project owner rightly rejected the commit as it is practically incomprehensible. What I should have done is broken down the diff into 6 different bite-sized commits.
So, I'd like to fix this now. I'd like to revert my last commit. I don't want to lose the changes - just to uncommit them, so that I can pick and choose the changes I want to include in new, smaller commits.
Can Sourcetree help me with that?