send-email: don't attempt to prompt if tty is closed

diff --git a/git-send-email.perl b/git-send-email.perl
index 5916c86b6874c5d39952fc9565ad0e24e301bbb9..d790660bcf7bdc68a8edee6a2826447da931a9cc 100755 (executable)
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -612,6 +612,9 @@ sub ask {
        my $default = $arg{default};
        my $resp;
        my $i = 0;
+       return defined $default ? $default : undef
+               unless defined $term->IN and defined fileno($term->IN) and
+                      defined $term->OUT and defined fileno($term->OUT);
        while ($i++ < 10) {
                $resp = $term->readline($prompt);
                if (!defined $resp) { # EOF