merge: before cd/dc prompt, check that changed side really changed Before, merging would in some cases ask "wrong" questions about "changed/deleted" conflicts ... and even do it before the resolve phase where they can be postponed, re"resolved" or answered in bulk operations. Instead, check that the content of the changed file really did change. Reading and comparing file content is expensive and should be avoided before the resolve phase. Prompting the user is however even more expensive. Checking the content here is thus better. The 'f in ancestors[0]' should not be necessary but is included to be extra safe.