Treat -ff without -o FILE as single -f

* strace.c (init): Treat -ff without -o FILE as single -f.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/strace.c b/strace.c
index e581882..27b64b0 100644
--- a/strace.c
+++ b/strace.c
@@ -1356,6 +1356,10 @@
 		}
 		else if (followfork <= 1)
 			outf = strace_fopen(outfname);
+	} else {
+		/* -ff without -o FILE is the same as single -f */
+		if (followfork > 1)
+			followfork = 1;
 	}
 
 	if (!outfname || outfname[0] == '|' || outfname[0] == '!') {