Have you ever been in a situation where a fix applied to one stream was urgently required in another?
This often happens when a bug fixed in a future release is escalated and needs to be included in a patch release. Each patch typically has its own stream so you need to merge the fix from the feature or mainline stream to the patch. To restrict the merged code to the exact bug-fix you need to cherrypick the changes carefully.
Dimensions CM 14.1.x and earlier supports regular request merge but not cherrypicking.