Explicit opt function arguments (#2817)

* more explicit function arguments

* fix typo in detect.py

* revert import order

* revert import order

* remove default value

detect.py

@@ -15,7 +15,7 @@ from utils.plots import plot_one_box
 from utils.torch_utils import select_device, load_classifier, time_synchronized
 
 
-def detect():
+def detect(opt):
     source, weights, view_img, save_txt, imgsz = opt.source, opt.weights, opt.view_img, opt.save_txt, opt.img_size
     save_img = not opt.nosave and not source.endswith('.txt')  # save inference images
     webcam = source.isnumeric() or source.endswith('.txt') or source.lower().startswith(
@@ -176,7 +176,7 @@ if __name__ == '__main__':
     with torch.no_grad():
         if opt.update:  # update all models (to fix SourceChangeWarning)
             for opt.weights in ['yolov5s.pt', 'yolov5m.pt', 'yolov5l.pt', 'yolov5x.pt']:
-                detect()
+                detect(opt=opt)
                 strip_optimizer(opt.weights)
         else:
-            detect()
+            detect(opt=opt)