# the given message.  If remote is invalid we will die
        # later in the common codepath so we discard the error
        # in this loop.
-       merge_name=$(for remote
+       merge_msg="$(
+               for remote
                do
                        merge_name "$remote"
-               done | git fmt-merge-msg $log_arg
-       )
-       merge_msg="${merge_msg:+$merge_msg$LF$LF}$merge_name"
+               done |
+               if test "$have_message" = t
+               then
+                       git fmt-merge-msg -m "$merge_msg" $log_arg
+               else
+                       git fmt-merge-msg $log_arg
+               fi
+       )"
 fi
 head=$(git rev-parse --verify "$head_arg"^0) || usage