One thing that could be useful for this is writing code locally and testing it on a remote server. I assume the simple act of editing reflects the change on the other machine? No need to commit, push, then pull to do a one-liner experimental change
Far too often I find myself making all my changes on my Windows box, or copying them to one destination, the other, or both. Then bug fixing on the local machine as part of my test cycle. Then I have a few moments of confusion when I try to remember what I changed where and how to pull them all back over to my Windows box.
So yeah, something like your proposed tool would be quite useful.
However, it solves the problem of when there are changes on both sides and you want to reconcile them.