The tree should display merge information by painting
arrows between revision.
The merge information can be decoded from tags attached
to revisions. These tags have to follow some sort of
pattern (e.g. by special prefixes: source_SOMENAME and
dest_SOMENAME).
Pairs of patterns for source and destination of a merge
should be specified by the user on the preference page.
Regular Expressions for the pattern specification would
be fine.
That has been implemented for 1.7.0