title: How to ignore some differences in diff command?
body: <p><code>diff</code> has an option <code>-I regexp</code>, which ignores changes that just insert or delete lines that match the given regexp. I need an analogue of this for the case, when changes are between two lines (rather then insert or delete lines).</p>
  
  <p>For instance, I want to ignore all differences like between <code>"abXd"</code> and <code>"abYd"</code>, for given <code>X</code> and <code>Y</code>.</p>
  
  <p>It seems <code>diff</code> has not such kind of ability. Is there any suitable alternative for <code>diff</code>?</p>