base_rev="$(git rev-parse --short --verify "refs/top-bases/$name" 2>/dev/null)" ||
die "not a TopGit-controlled branch"
+if ! git send-email --help >/dev/null 2>&1; then
+ die "git send-email command not available"
+fi
+
if [ -n "$in_reply_to" ]; then
send_email_args="$send_email_args --in-reply-to=$in_reply_to"
fi