Two files both added some lines, but no change in other lines
diff -Naur index/ ~/icwiki/index/ > icwiki-patch.diff patch -Rp0 --merge < ~/learnspace/git-mylife/icwiki/icwiki-patch.diff
NOTE: you can
--dry-run for previous command to see what the effect might
be, however, you are still encouraged to backup your to-be-patched files.