Packfiles and deltas are a storage and transfer optimization for blobs. Any access to them store and yield blobs. It is for all intents and purposes just an in

Packfiles and deltas are a storage and transfer optimization for blobs. Any access to them store and yield blobs. It is for all intents and purposes just an internal serialization format, akin to how a filesystem is just a serialization format that makes all your data one large stream. One generally talks about the provided interface (files for a filesystem, blobs for git) rather than where the bits actually go. Compression algorithms are also to some extend diffs as they serialize to a sequence of "repeat previous segment and add this new data" commands, but it is not useful to consider them as such.