filter-branch: avoid passing commit message through sed

diff --git a/RelNotes b/RelNotes
index f60e868f4721b24cfe989303193bf0a9be3473a7..5696e88ad5f86cac0e7095469e8d705337c91e2e 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.6.5.8.txt
\ No newline at end of file
+Documentation/RelNotes/2.0.5.txt
\ No newline at end of file