Don't expose GChecksum in APIs. Add a new stream class which allows
us to pass an input stream somewhere, but gather a checksum as it's
read.
Move some bits of the internals towards binary csums.
I'm trying to keep ostree as being closer to just being the versioning
filesystem, so let's split out the triggers into a different binary
(although still namespaced ostree-).
The tar import code forced the resuscitation of a hackish "FileTree"
data type for representing an in-memory tree. Split this out
into an OstreeMutableTree class for future use by any other in-memory
tree construction.
Colin Walters