Which RPM does mergerepo prefer?

[Jitesh Shah]

Hi,
I have attached an external repo to a build tag (Just trying out some
hand-built RPMs). Now, if an RPM is present *both* in the build tag as
well as the external repo, which one does mergerepos pick?

Is the decision based on version comparison (the greater version wins),
or does the one in the build tag always get preference over the external
repo (irrespective of the version)?

If it is the latter, how do I tell mergerepos to prefer external repo
over the build tag? (or atleast use version comparisons rather than
preferring build tag)

Jitesh