use bytesize

Author: okhwaja

book/10-git-internals/sections/objects.asc

@@ -370,7 +370,7 @@ To that first part of the header, Git adds a space followed by the size in bytes
 
 [source,console]
 ----
->> header = "blob #{content.length}\0"
+>> header = "blob #{content.bytesize}\0"
 => "blob 16\u0000"
 ----