Subrepository changeset links are broken (BB-4882)

If you go to a repository that contain subrepositories, such as

• https://bitbucket.org/tortoisehg/thg-build/src

then you see nice links to the subrepos. The links to the subrepos themselves are fine, but the links to the changesets (the link in square brackets) has a doubled slashes:

• https://bitbucket.org/abderrahim/dulwich//changeset/71b73697d24b

Clicking the link gives a 404 error.

The spacing between subrepo name and the square brackets is also inconsistent: if the subrepo revision is not a link, the leading space is missing.