Furgit, fast Git library in pure Go, re-structured

Current features: Parsing configs Object ID and hash algorithms (SHA-256, SHA-1) Object type enums Object representation types Object header parsing Parsing objects Serializing objects Diffing lines Diffing trees Object storer interface Reading loose objects Applying deltas .idx lookup Reading packed objects Object storer chain and mixer Ref types Ref storer interface Reading loose refs Reading packed refs Ref storer chain Reachability iterators Repository abstractions Adler-32 optimizations ZLIB pooling Streaming .pack/.idx hash verifier .idx and .rev writing Pack ingestion Un-thinning thin packs