checkincludes.pl: provide usage helper

Signed-off-by: NLuis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

scripts/checkincludes.pl

@@ -3,6 +3,15 @@
 # checkincludes: Find files included more than once in (other) files.
 # Copyright abandoned, 2000, Niels Kristian Bech Jensen <nkbj@image.dk>.
 
+sub usage {
+	print "Usage: checkincludes.pl <file list>\n";
+	exit 1;
+}
+
+if ($#ARGV < 0) {
+        usage();
+}
+
 foreach $file (@ARGV) {
 	open(FILE, $file) or die "Cannot open $file: $!.\n";