The only use is in `builder/builder-next/adapters/snapshot.EnsureLayer()`,
which always calls the function with an _empty_ `oldTarDataPath`;
7082aecd54/builder/builder-next/adapters/snapshot/layer.go (L81)
When called with an empty `oldTarDataPath`, this function was an alias for
`checksumForGraphIDNoTarsplit`, so let's make it that.
Note that this code was added in 500e77bad0, as
part of the migration from "v1" images to "v2" (content-addressable) images.
Given that the remaining code lives in a "migration" file, possibly more code
can be removed.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
782fe1fe82