[Svnmerge] request for review: #2863 - analyze_source_revs fix

[Dustin J. Mitchell]

This is a tiny patch, but fixes incorrect behavior when merging between
two repositories -- analyze_source_revs previously looked for the head
revision of the *target* when trying to determine the highest possible
revision, but it is responsible for analyzing revisions in the *source*.

Again, any comments and/or review will be appreciated.

Patch is attached and at
http://subversion.tigris.org/nonav/issues/showattachment.cgi/696/get_latest_rev_of_source.patch

-- 
        Dustin J. Mitchell
        Storage Software Engineer, Zmanda, Inc.
        http://www.zmanda.com/