Add git info to cls, seg checkpoints (#10217)

train.py

@@ -376,7 +376,7 @@ def train(hyp, opt, device, callbacks):  # hyp is path/to/hyp.yaml or hyp dictio
                     'updates': ema.updates,
                     'optimizer': optimizer.state_dict(),
                     'opt': vars(opt),
-                    'git': GIT,
+                    'git': GIT,  # {remote, branch, commit} if a git repo
                     'date': datetime.now().isoformat()}
 
                 # Save last, best and delete