diff --old-line-format "<Diff></Diff>%c'\012'" \
     --new-line-format "<Diff>%l</Diff>%c'\012'" \
     File1.txt File2.txt > NewFile1.txt

diff --old-line-format "<Diff>%l</Diff>%c'\012'" \
     --new-line-format "<Diff></Diff>%c'\012'" \
     File1.txt File2.txt > NewFile2.txt