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

diff --git a/RelNotes b/RelNotes
index 3d420845b117b3f3eb82d1f0948a61c7989d8af9..fce99fb79d16cbeb717ddbe36c7be231a00e4eba 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.6.1.txt
\ No newline at end of file
+Documentation/RelNotes/1.8.4.txt
\ No newline at end of file