Merge branch 'np/pack'

* np/pack:
  add the capability for index-pack to read from a stream
  index-pack: compare only the first 20-bytes of the key.
  git-repack: repo.usedeltabaseoffset
  pack-objects: document --delta-base-offset option
  allow delta data reuse even if base object is a preferred base
  zap a debug remnant
  let the GIT native protocol use offsets to delta base when possible
  make pack data reuse compatible with both delta types
  make git-pack-objects able to create deltas with offset to base
  teach git-index-pack about deltas with offset to base
  teach git-unpack-objects about deltas with offset to base
  introduce delta objects with offset to base

cache.h

@@ -269,8 +269,9 @@ enum object_type {
 	OBJ_TREE = 2,
 	OBJ_BLOB = 3,
 	OBJ_TAG = 4,
-	/* 5/6 for future expansion */
-	OBJ_DELTA = 7,
+	/* 5 for future expansion */
+	OBJ_OFS_DELTA = 6,
+	OBJ_REF_DELTA = 7,
 	OBJ_BAD,
 };