How ClearCase merges

To merge versions, Rational® ClearCase® takes the following steps:

1. It identifies the base contributor.
2. Next, it compares each contributor against the base contributor.
3. For any line that is unchanged between the base contributor and any other contributor, Rational ClearCase copies the line to the merge output file.
4. For any line that has changed between the base contributor and another contributor, Rational ClearCase performs a trivial merge by accepting the change in the contributor. Note, however, that depending on how you started the merge operation, Rational ClearCase may copy the change to the merge output file. However, you can disable the automated merge capability for any given merge operation. If you disable this capability, you must approve each change to the merge output file.
5. For any line that has changed between the base contributor and more than one other contributor, Rational ClearCase requires that you resolve the conflicting difference.