If branch name has special character, "View revisions" link has route error.
For example, Redmine Mercurial hgsubversion mirror has "../sandbox/rails-3.2" named branch.
Git default branch of bare repository is defined at HEAD.
In most cases, it is *master*.
Mercurial GUI standard behavior is showing all revisions on top page.
So, Redmine default branch is *nil*.
Mercurial top page "View revisions" link has route error.
