do not write null sha1s to on-disk index

diff --git a/RelNotes b/RelNotes
index c150f36749e0ac78acc95f794b03c9bf5688c6d1..3f4ce9f4f14e45b9bb20577be8d63da79174cb4f 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.7.0.7.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.9.6.txt
\ No newline at end of file