Function write_git_binary_patch_sections 

pub fn write_git_binary_patch_sections<W: Write>(
    out: &mut W,
    old: &[u8],
    new: &[u8],
) -> Result<()>

Write the GIT binary patch body (literal forward then reverse) to out.

Forward literal is new; reverse literal is old, matching Git’s git diff --binary. The index line and diff --git header are the caller’s responsibility.