Minor Description
It would be very handy if the CSV loader could handle a literal field mapping, like the extracting request handler does. For example, in a scenario where you have multiple datasources (some data from a DB, some from file crawls, and some from CSV) it is nice to add a field to every document that specifies the data source. This is easily done with DIH with a template transformer, and Solr Cell with ext.literal.datasource=, but impossible currently with CSV.