bash: add '--merge' to 'git reset'

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index e004549..3b25d48 100755
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -1403,7 +1403,7 @@
 	local cur="${COMP_WORDS[COMP_CWORD]}"
 	case "$cur" in
 	--*)
-		__gitcomp "--mixed --hard --soft"
+		__gitcomp "--merge --mixed --hard --soft"
 		return
 		;;
 	esac