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

diff --git a/RelNotes b/RelNotes
index 2dad8b277db3a95919bd904133d7e7cc3e323cb9..fce99fb79d16cbeb717ddbe36c7be231a00e4eba 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.6.4.4.txt
\ No newline at end of file
+Documentation/RelNotes/1.8.4.txt
\ No newline at end of file