Check for duplicate dataId/datasetType ingest requests

This can happen if by some chance someone asks the same file
to be ingested from two different locations.

python/lsst/daf/butler/_butler.py

@@ -1433,6 +1433,10 @@ def ingest(self, *datasets: FileDataset, transfer: Optional[str] = "auto", run:
             # associated with `dataset`.
             resolvedRefs: List[DatasetRef] = []
             for ref in dataset.refs:
+                if ref.dataId in groupedData[ref.datasetType]:
+                    raise RuntimeError(f"Ingest conflict. Dataset {dataset.path} has same DataId as "
+                                       f"other ingest dataset"
+                                       f" {groupedData[ref.datasetType][ref.dataId][0].path} ({ref.dataId})")
                 groupedData[ref.datasetType][ref.dataId] = (dataset, resolvedRefs)
 
         # Now we can bulk-insert into Registry for each DatasetType.