Is there any way to specify which branch the code metrics and package information is collected from ?
No, the code-metrics and info-file includes gather data from the running code base.
In order to get info from other branches, we'd need to get that info from CVS, meaning we'd have to have a nice way to access CVS information. The info-file include wouldn't be hard to do, but the code metrics would involve checking out full versions of each branch so we could do counts of procs, lines and pages.