stripping the head commit on a git repository breaks browsing the source tree

An active example of this is: http://bitbucket.org/tortoiselabs/panel2

We had an error in a commit message so did a git commit --amend to fix it, followed by a git push --force to strip the old master commit out of the repository.

Now all links refer to the old broken commit, even though the master branch has advanced past that point.