1. I set up a hosted Mercurial repository.
2. I removed the head commit from the on-disk repository state.
3. I attempted to load the repository page and saw an exception due to a missing commit.
4. I went to `/manage` for the repository and scheduled an update of the repository.
5. After an updated performed, I went to the repository main page and saw there was no exception and the history view properly did not have the commit I had removed.
6. I checked the phd logs and verified there were no exceptions related to the repository.
7. I ran the `./bin/repository mark-reachable` command on the Mercurial repository and it reported that it marked the commit as unreachable
8. I pushed the same commit back upstream and verified that the commit was found and displayed in the history view of the repository page and `mark-unreachable` did not identify it as being unreachable.