Function write_bitmap 

pub fn write_bitmap(
    format: ObjectFormat,
    pack_checksum: ObjectId,
    object_types: &[ObjectType],
    commits: &[(u32, u32, Vec<u32>)],
    name_hash_cache: Option<Vec<u32>>,
) -> Result<Vec<u8>>

Convenience wrapper that builds a .bitmap file in one call.

object_types lists the ObjectType of every pack object in pack order, pack_checksum is the pack’s trailing checksum, and commits carries, per selected commit, (pack_position, index_position, reachable_pack_positions) (see PackBitmapWriter::add_commit for the two position spaces). An optional name_hash_cache (one entry per object) may be supplied to emit the hash-cache extension.