dvc: warn to run dvc checkout --relink in cache.type change

dvc/command/config.py

@@ -29,6 +29,15 @@ class CmdConfig(CmdBaseNoRepo):
                 section, opt, self.args.value, level=self.args.level
             )
 
+        is_write = self.args.unset or self.args.value is not None
+        if is_write and self.args.name == "cache.type":
+            logger.warning(
+                "You have changed cache.type, this doesn't update link types "
+                "of any previously checked out files automatically. "
+                "That can be done with:\n"
+                "             dvc checkout --relink"
+            )
+
         return 0