Add option -? for usage to diffimg

diff --git a/contrib/diffimg/diffimg.c b/contrib/diffimg/diffimg.c
index 12a6cfe685f5bdf878fdd955888eac43d917d47d..ca9117911ea1b1d92c0e2d7b48d83b253a19cd8a 100644 (file)
--- a/contrib/diffimg/diffimg.c
+++ b/contrib/diffimg/diffimg.c
@@ -164,6 +164,10 @@ int main(int argc, char **argv)
     FILE *f;
 #endif
 
+    if (argc == 2 && strcmp(argv[1], "-?") == 0) {
+        fprintf(stderr, "Usage: diffimg image1 image2 [outimage]\n");
+        exit(0);
+    }
     if (argc < 3) {
         fprintf(stderr, "Usage: diffimg image1 image2 [outimage]\n");
         exit(EX_USAGE);