--ignore-space-change
--ignore-all-space
--ignore-space-at-eol

git config mergetool.cp.cmd '/bin/cp -v "$REMOTE" "$MERGED"'
git config mergetool.cp.trustExitCode true

git mergetool --tool=cp
git mergetool --tool=cp -- paths/to/files.txt
git mergetool --tool=cp -y -- paths/to/files.txt # without prompting

git checkout HEAD -- path/to/myfile.txt

git checkout remote/branch_to_merge -- path/to/myfile.txt