SHA-1("TREE" + <binary representation of N> +
"REUC" + <binary representation of M>)
+
+== Index Entry Offset Table
+
+ The Index Entry Offset Table (IEOT) is used to help address the CPU
+ cost of loading the index by enabling multi-threading the process of
+ converting cache entries from the on-disk format to the in-memory format.
+ The signature for this extension is { 'I', 'E', 'O', 'T' }.
+
+ The extension consists of:
+
+ - 32-bit version (currently 1)
+
+ - A number of index offset entries each consisting of:
+
+ - 32-bit offset from the begining of the file to the first cache entry
+ in this block of entries.
+
+ - 32-bit count of cache entries in this block