ryan.timmons discovered that passing a bson array as the pipeline argument to mongoc_collection_watch silently fails to append anything and is the same as if no pipeline was passed.

This is because the pipeline must be passed as a document like

{ "pipeline": [...] }

This is partially consistent with the pipeline argument to mongoc_collection_aggregate, but mongoc_collection_aggregate also allows a bson array. mongoc_collection_watch should be consistent with the aggregate helper and allow either way to pass a pipeline.