Don’t I know it. MergeCrv is documented, but it has more issues than Joincopy. I’ve been begging for someone to look at either of them, but to no avail.
They both came from my feature request that somehow became two youtracks:
https://mcneel.myjetbrains.com/youtrack/issue/RH-45817
https://mcneel.myjetbrains.com/youtrack/issue/RH-56306