POSIX only requires sed to work on text files and MERGE_RR is not a text
file. Some versions of sed complain that this file is not newline
terminated, and exit non-zero. Use perl instead which does not have a
problem with it.
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil> Signed-off-by: Junio C Hamano <gitster@pobox.com>