You can select all unmerged changes from older to yours for merging into mine with the --ed (-e) option. You can select only the nonoverlapping unmerged changes with --easy-only (-3), and you can select only the overlapping changes with --overlap-only (-x).
The -e, -3 and -x options select only unmerged changes, i.e. changes where mine and yours differ; they ignore changes from older to yours where mine and yours are identical, because they assume that such changes have already been merged. If this assumption is not a safe one, you can use the --show-all (-A) option (see Marking Conflicts).
Here is the output of the command diff3 with each of these three
options (see A Third Sample Input File, for the complete contents of the files).
Notice that -e outputs the union of the disjoint sets of changes
output by -3 and -x.
Output of ‘diff3 -e lao tzu tao’:
11a -- The Way of Lao-Tzu, tr. Wing-tsit Chan . 8c so we may see their result. .
Output of ‘diff3 -3 lao tzu tao’:
8c so we may see their result. .
Output of ‘diff3 -x lao tzu tao’:
11a -- The Way of Lao-Tzu, tr. Wing-tsit Chan .