git-am: remove dash from help message

Signed-off-by: Olivier Marin <dkr@freesurf.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-am.sh b/git-am.sh
index 9bf12fe..fcbffb2 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -44,7 +44,7 @@
 	    printf '%s\n' "$resolvemsg"
 	    stop_here $1
     fi
-    cmdline=$(basename $0)
+    cmdline="git am"
     if test '' != "$interactive"
     then
         cmdline="$cmdline -i"