gc: reject if another gc is running, unless --force is given

diff --git a/RelNotes b/RelNotes
index 573ee74d24fb63ae5394d33efc06c2e3c3a0542e..155555ef6af91ee7309a047f8280c1c57cac1e62 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.7.1.2.txt
\ No newline at end of file
+Documentation/RelNotes/1.8.2.3.txt
\ No newline at end of file