Function resolve_against 

pub fn resolve_against<'b>(
    e: &'b EmitEntry,
    archive: &'b [u8],
) -> Result<&'b [u8]>

One entry’s bytes, resolved against a buffer that spans the archive’s coordinate space — the in-memory resolver, and the one emit_pack’s callers use when the archive is a &[u8] rather than a mapping.

The mapped path is crate::git_ops::GitStore::resolve_emit_payloads; this is the same two-arm decision over a slice, written once so that a test fixture and a hand-built pack cannot drift from what a served clone does (LAW 5). An extent that runs off the buffer is an error and never a short slice, for the reason [crate::archive_map::Mapped::get] gives: a truncated entry spliced into a pack is data the client will only reject much later.