Isn't that violating 'doing one thing'? (Your other examples in this point are valid, and serve to show how powerful building concepts on top of a few primitives can be, if confusing at times)
Git checkout is a command to read something from your .git-folder to your working directory.
Especially for people coming from ClearCase, the concept of Git checkout needs to be clarified as fast as possible. (In CC checkout means you make an element (file) editable for you, and possibly reserve it to you too)
Yes. But that violation would also be there if `git branch` would checkout. And in that sense, what's more odd "git checkout -b new-branch" or "git branch --checkout new-branch"?