Side note but what is going on with this projects commits?
https://public-001.gitsense.com/insights/github/repos?p=comm...
Click on a file to bring up the diffs browser.
Disclaimer: I'm the creator of the tool that I'm linking to.
But thanks for the tip about Emacs undo tree, didn't know about that. With some add-ons you can apparently eg find undoable changes for only some region of a buffer, etc.
This is built into Emacs (no add-ons needed). Calling undo with a region selected undoes changes only in that region.