diff-index.c: "git diff" has no need to read blob from the standard input

diff --git a/RelNotes b/RelNotes
index 115c33553bb99a5ac6c21c2ac0f33ab7b48a4901..fb9320b14baeae5fdb759a99e7edb77546cd5bc1 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.6.5.6.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.6.6.txt
\ No newline at end of file