fallback to existing model.root_path behaviour for seed loading

core/dbt/context/providers.py

@@ -870,6 +870,9 @@ def load_agate_table(self) -> agate.Table:
             else "."
         )
         path = os.path.join(self.config.project_root, package_path, self.model.original_file_path)
+        if not os.path.exists(path):
+            assert self.model.root_path
+            path = os.path.join(self.model.root_path, self.model.original_file_path)
 
         column_types = self.model.config.column_types
         delimiter = self.model.config.delimiter

core/dbt/contracts/graph/nodes.py

@@ -875,7 +875,6 @@ class SeedNode(ParsedNode):  # No SQLDefaults!
     config: SeedConfig = field(default_factory=SeedConfig)
     # seeds need the root_path because the contents are not loaded initially
     # and we need the root_path to load the seed later
-    # TODO: remove root_path as it is unused, and instead computed dynamically in load_agate_table
     root_path: Optional[str] = None
     depends_on: MacroDependsOn = field(default_factory=MacroDependsOn)
     defer_relation: Optional[DeferRelation] = None