What I probably want is git update-index --skip-worktree [path]. Now that's screwy because it won't see updates either. What I really want is --dont-push-my-idiosyncratic-changes, but this'll have to do for now.
Undoing is apparently git update-index --no-skip-worktree [path]. Kinda feels like when I learned how to unset settings in VIm -- `:set nolist`.