add: tweak stage overlap error message (#9514)

* add: tweak stage overlap error message

* add: instructions for how to fix overlap error

dvc/repo/add.py

@@ -32,6 +32,12 @@
     from dvc.stage import Stage
 
 
+PIPELINE_TRACKED_UPDATE_FMT = (
+    "cannot update {out!r}: overlaps with an output of {stage} in '{path}'.\n"
+    "Run the pipeline or use 'dvc commit' to force update it."
+)
+
+
 class StageInfo(NamedTuple):
     stage: "Stage"
     output_exists: bool
@@ -91,7 +97,10 @@ def get_or_create_stage(
         (out_obj,) = repo.find_outs_by_path(target, strict=False)
         stage = out_obj.stage
         if not stage.is_data_source:
-            raise DvcException(f"cannot update {out!r}: not a data source")
+            msg = PIPELINE_TRACKED_UPDATE_FMT.format(
+                out=out, stage=stage, path=stage.relpath
+            )
+            raise DvcException(msg)
         return StageInfo(stage, output_exists=True)
     except OutputNotFoundError:
         stage = repo.stage.create(

tests/func/test_add.py

@@ -722,7 +722,11 @@ def test_add_optimization_for_hardlink_on_empty_files(tmp_dir, dvc, mocker):
 def test_try_adding_pipeline_tracked_output(tmp_dir, dvc, run_copy):
     tmp_dir.dvc_gen("foo", "foo")
     run_copy("foo", "bar", name="copy-foo-bar")
-    with pytest.raises(DvcException, match="cannot update 'bar': not a data source"):
+    msg = (
+        "cannot update 'bar': overlaps with an output of stage: 'copy-foo-bar' in "
+        "'dvc.yaml'.\nRun the pipeline or use 'dvc commit' to force update it."
+    )
+    with pytest.raises(DvcException, match=msg):
         dvc.add("bar")