You can use smudge and clean filters to expand this into something on disk and then remove it again before the hash computation runs. However, I don't think yo

You can use smudge and clean filters to expand this into something on disk and then remove it again before the hash computation runs. However, I don't think you would want to use the SHA, since that's somewhat meaningless to read. You would probably want to expand ID to `git describe SHA` so it's more like `v1.0.1-4-ga691733dc`, so you can see something more similar to a version number.