The specification now clearly documents how to support binary diffs

using three methods:

VCDIFFs (recommended)
Git Delta diffs
Git Literal diffs

VCDIFFs (RFC 3284) are a standardized binary format for representing

patches to binary files. It includes instructions for adding a sequence

of new bytes, adding a single byte N times, and copying bytes from a

source to a target. The format allows for future extensibility.
Git Delta diffs are similar to VCDIFFs in concept, but more limited.

They contain instructions for adding a sequence of new bytes and for

copying bytes from a source to a target. They do not include any

run-length encoding instructions, and are not built to be extended for

new instructions in the future, but its structure is overall more

compact than VCDIFFs.
Git Literal diffs simply contain the full contents of the patched file.
In all three cases, diffs are expected to contain a forward patch and a

reverse patch. The binary contents of each represent the payloads of the

above formats, compressed using zlib, Base85-encoded, and then split

across lines with encoded length indicators.
The specification includes instructions for encoding and decoding each

format (deferring to RFC 3284 for VCDIFF, and documenting the formats

for Git Deltas and Literals).

Built the spec. Checked for spelling errors, grammatical errors, and

bad links.
Code samples came from test code used to validate the encoding/decoding

logic. Those code samples are not included at this time, as they need

further cleanup.