bash prompt: combine 'git rev-parse' for detached head

diff --git a/RelNotes b/RelNotes
index b630faa0c0f46c5650668a014e2734b0bfe0f8a5..fce99fb79d16cbeb717ddbe36c7be231a00e4eba 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.5.1.3.txt
\ No newline at end of file
+Documentation/RelNotes/1.8.4.txt
\ No newline at end of file