Redmine

The 'copy' relationship does not represent actual dependencies between Issues, but rather a way a particular issue was created. Copying is often done between issues which are not logically related (for instance, just to save time to fill in certain 'Defect' fields; still, defects themselves are not related). All other types of relations in Redmine are 'real', in a sense that they reflect actual dependencies affecting project execution and planning. The 'copy' relationship, on the other hand, obfuscates real dependencies between issues, and therefore is recommended to be removed.