revlog: document v0 format

mercurial/revlog.py

@@ -91,6 +91,14 b' def decompress(bin):'
         return bin[1:]
     raise RevlogError(_("unknown compression type %r") % t)
 
+# index v0:
+#  4 bytes: offset
+#  4 bytes: compressed length
+#  4 bytes: base rev
+#  4 bytes: link rev
+# 32 bytes: parent 1 nodeid
+# 32 bytes: parent 2 nodeid
+# 32 bytes: nodeid
 indexformatv0 = ">4l20s20s20s"
 v0shaoffset = 56