Add --no-ignore option

This suppresses the optimisation of ignoring conflicts which appear to
be making a change that had already been made.

Signed-off-by: NeilBrown <neilb@suse.de>
# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#	modified:   ReadMe.c
#	modified:   merge2.c
#	modified:   vpatch.c
#	modified:   wiggle.1
#	modified:   wiggle.c
#	modified:   wiggle.h
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	.patches
#	.version-man
#	.version-readme
#	DIST/
#	RCS/
#	ReadMe.o
#	TAGS
#	bestmatch.o
#	diff.o
#	extract.o
#	load.o
#	merge.o
#	merge2.o
#	notes.p
#	split.o
#	vpatch.o
#	wiggle
#	wiggle.man
#	wiggle.o
