I can see the similarity, though Git seems like an interesting differentiating example. Technically, it is extremely simple. A commit is a file tree with conten

I can see the similarity, though Git seems like an interesting differentiating example. Technically, it is extremely simple. A commit is a file tree with content stored in blobs along with a reference to the previous commit. A branch is the id of the blob containing the commit. Yet, it is frequently astonishing. The layers of porcelain over the plumbing are testament to the fact that the underlying model does not map to how you expect to work with a version control system, whether that's due to previous experience to due to an "impedance mismatch" with the way people actually work. Don't get me wrong, I happily use Git since I'm willing to bend my will to the machine in this way. It does realize its promise. A great example that's in the intersection of both is copy/cut/paste. That was the result of a user study for the Alto, I believe, watching real copyeditors doing their work. And it's technically straightforward. In contrast, the Emacs kill ring and undo system, together, trip me up even after years of use. They are technically elegant, but together create some astonishing situations. Like Git, all are easily fixable, yet still there is some friction. The PoLA, in its best form, seems to me to be about whether a user's will can be realized in as direct a way as possible. This might, potentially, have a very complicated implementation.