Add branch names for pushes on non-default branches

[KwanEsq]

Not sure if I did the right thing with the BugInfo.add_changeset

[glandium]

Theoretically speaking, a push could have multiple changesets all on different branches. So the branch should be attached to all changesets. Then when creating the bugzilla message, some kind of per branch aggregation should occur.

So a bugzilla message could look like:

Pushed by foo@bar.com on the branch foo:
https://server/repo/rev/6e4e7985aba3
Foo
https://server/repoa/rev/1234567890ab
Bar

Pushed by foo@bar.com on the branch qux:
https://server/repoa/rev/234567890abc
Qux

Or some other variation where branches are not repeated. Typical pushes would only have something like the first half.

[KwanEsq]

Not sure if the complicated branch_info assignment is worth it just to word the default branch slightly differently. Or maybe it should just be

                        branch_info = ' on the branch %s' % branch if \
                            has_branches and branch != 'default' else ''

could also do
'branch': cs.get('branch', 'default'),
in BugInfo.add_changeset instead of in bugzilla_reporter, for a slightly more complicated any()