Git could not do this (automatically stashing and unstashing) in a backwards-compatible fashion, but it could be opt-in with a new config key and does seem like

Git could not do this (automatically stashing and unstashing) in a backwards-compatible fashion, but it could be opt-in with a new config key and does seem like a very useful feature. It also seems like one that should be relatively easy to implement as all the main logic to actually stash and unstash is already part of Git, it would merely need to be saved to a different ref than refs/stash, so all it needs is someone with enough interest to actually implement it.