remote-bzr: add support for bzr repos

In bazaar, a repository can contain multiple branches, and previously we
were supporting only one branch at a time. Now we fetch them all.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: fix branch names

When branches have '/' in their name (aka. sub-branches), bazaar seems
to choke while creating the new directory.

Also, git cannot have both 'foo' and 'foo/bar'.

So let's replace slashes with a plus sign.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: add support for shared repo

This way all the remotes share the same data, so adding multiple
remotes, or renaming them doesn't create extra overhead.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: improve author sanitazion

So that we don't end up with '<None>', and also synchronize it with the
one from remote-hg.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: add custom method to find branches

The official method is incredibly inefficient and slow.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: add option to specify branches

We might not want all the branches. And branch handling in bazaar is
rather tricky, so it's safer to simply specify them.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: improve progress reporting

No need to manually count the revisions, and also, this would help to
iterate more properly.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: iterate revisions properly

This way we don't need to store the list of all the revisions, which
doesn't seem to be very memory efficient with bazaar's design, for
whatever reason.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: delay peer branch usage

So it doesn't time out.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
remote-bzr: access branches only when needed

Bazaar doesn't seem to be tested for multiple usage of branches, so
resources seem to be leaked all over. Let's try to minimize this by
accessing the Branch objects only when needed.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>