only close stdin when we read arguments from it

tests

@@ -1,5 +1,5 @@
 #!/bin/sh
-printf '1..38\n'
+printf '1..40\n'
 
 set -e
 
@@ -215,6 +215,15 @@ a
 123
 EOF
 
+check_output 'should close stdin when arguments were read from it' 'necho a b c | $XE -s "sed q"' <<EOF
+EOF
+
+check_output 'should not close stdin when arguments were read from command line' 'yes | $XE -a -s "sed q" -- 1 2 3' <<EOF
+y
+y
+y
+EOF
+
 printf '# limit checks, expecting maximal POSIX limits available\n'
 
 check_output 'argscap check' 'head -c 17711 /dev/zero | tr "\0" "\012" | $XE -N0 -s "echo \$#"' <<EOF

xe.c

@@ -205,14 +205,16 @@ run()
 		char iter[32];
 		snprintf(iter, sizeof iter, "%ld", iterations);
 		setenv("ITER", iter, 1);
-		// redirect stdin to /dev/null
-		int fd = open("/dev/null", O_RDONLY);
-		if (fd >= 0) {
-			if (dup2(fd, 0) != 0)
-				exit(1);
-			close(fd);
-			execvp(args[0], args);
+		// redirect stdin to /dev/null when we read arguments from it
+		if (!(aflag || Aflag)) {
+			int fd = open("/dev/null", O_RDONLY);
+			if (fd >= 0) {
+				if (dup2(fd, 0) != 0)
+					exit(1);
+				close(fd);
+			}
 		}
+		execvp(args[0], args);
 		fprintf(stderr, "xe: %s: %s\n", args[0], strerror(errno));
 		exit(errno == ENOENT ? 127 : 126);
 	}