Allow YOLOv5 execution from arbitrary cwd (#4954)

* Allow YOLOv5 execution from arbitrary `cwd`

* Fix str bugs

val.py

@@ -21,6 +21,7 @@ FILE = Path(__file__).resolve()
 ROOT = FILE.parents[0]  # YOLOv5 root directory
 if str(ROOT) not in sys.path:
     sys.path.append(str(ROOT))  # add ROOT to PATH
+ROOT = ROOT.relative_to(Path.cwd())  # relative
 
 from models.experimental import attempt_load
 from utils.datasets import create_dataloader
@@ -95,7 +96,7 @@ def run(data,
         save_hybrid=False,  # save label+prediction hybrid results to *.txt
         save_conf=False,  # save confidences in --save-txt labels
         save_json=False,  # save a COCO-JSON results file
-        project='runs/val',  # save to project/name
+        project=ROOT / 'runs/val',  # save to project/name
         name='exp',  # save to project/name
         exist_ok=False,  # existing project/name ok, do not increment
         half=True,  # use FP16 half-precision inference
@@ -297,8 +298,8 @@ def run(data,
 
 def parse_opt():
     parser = argparse.ArgumentParser()
-    parser.add_argument('--data', type=str, default='data/coco128.yaml', help='dataset.yaml path')
-    parser.add_argument('--weights', nargs='+', type=str, default='yolov5s.pt', help='model.pt path(s)')
+    parser.add_argument('--data', type=str, default=ROOT / 'data/coco128.yaml', help='dataset.yaml path')
+    parser.add_argument('--weights', nargs='+', type=str, default=ROOT / 'yolov5s.pt', help='model.pt path(s)')
     parser.add_argument('--batch-size', type=int, default=32, help='batch size')
     parser.add_argument('--imgsz', '--img', '--img-size', type=int, default=640, help='inference size (pixels)')
     parser.add_argument('--conf-thres', type=float, default=0.001, help='confidence threshold')
@@ -312,14 +313,14 @@ def parse_opt():
     parser.add_argument('--save-hybrid', action='store_true', help='save label+prediction hybrid results to *.txt')
     parser.add_argument('--save-conf', action='store_true', help='save confidences in --save-txt labels')
     parser.add_argument('--save-json', action='store_true', help='save a COCO-JSON results file')
-    parser.add_argument('--project', default='runs/val', help='save to project/name')
+    parser.add_argument('--project', default=ROOT / 'runs/val', help='save to project/name')
     parser.add_argument('--name', default='exp', help='save to project/name')
     parser.add_argument('--exist-ok', action='store_true', help='existing project/name ok, do not increment')
     parser.add_argument('--half', action='store_true', help='use FP16 half-precision inference')
     opt = parser.parse_args()
+    opt.data = check_yaml(opt.data)  # check YAML
     opt.save_json |= opt.data.endswith('coco.yaml')
     opt.save_txt |= opt.save_hybrid
-    opt.data = check_yaml(opt.data)  # check YAML
     print_args(FILE.stem, opt)
     return opt