Fix fetching GitHub branch names containing slashes.

Review Request #5983 — Created June 11, 2014 and submitted — Latest diff uploaded

Information

Review Board
release-2.0.x
ae60794...

Reviewers

Git branches can contain slashes, but our GitHub support was stripping
them off. We now support showing the entire branch name, slashes
included, by stripping off the leading 'refs/heads/' instead of
splitting on '/' and getting the last component.

The new additions to the unit test failed before this, but passed after.