Hi, Gerry-
Here's a quote from MacColl-Seeger, Travellers' Songs from England and Scotland:

The earliest reported text of the ballad is a two-stanza fragment in the Herd MSS, entitled "My Love Is Lang a-Growing." This was used by Burns as the basis of "Lady Mary Ann," a song written for the Scots Musical Museum (1787). In a note to the Burns song, James Dick reports that a "tune entitled 'Long A-Growing' is said to be in Guthrie's MSS (c. 1670)."

I gather that by the term "lumper," Bob Waltz of the Traditional Ballad Index means that MacColl & Seeger, Kennedy, Roud, and others tend to lump unrelated songs together if they share only a few elements. Search the Ballad Index for "lumper" and "lumped," and you'll find some interesting comments.
-Joe Offer-