It's been a long standing issue and I've really become tired of
switching my repository_dir setting manually in order to browse for my
local changesets in the many local branches I have, so ...
I've taken a shot at implementing multiple repository support. Things
went surprisingly smooth, mainly because I decided to keep the
repository cache topic completely aside for now. But if you want to
directly browse many Subversion and/or Mercurial repositories, within
one big virtual namespace (repository names are used as disambiguation
prefixes for paths and as suffixes for changesets), you will surely be
interested by this branch.
More information in http://trac.edgewall.org/wiki/MultipleRepositorySupport
-- Christian