merge-recursive: drop several unused parameters

merge-recursive: drop several unused parameters

There are a few functions related to directory renames that have unused
parameters. After consulting with the author in [1], these seem to be
leftover cruft from the development process, and not signs of any bug.
Let's drop them.

[1] https://public-inbox.org/git/CABPp-BHobf8wbBsXF97scNQCzkxQukziODRXq6JOOWq61cAd9g@mail.gmail.com/

Helped-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>