Need to edit lib/redmine/scm/adapters/mercurial_adapter.rb on some servers
I've been advised to report this as a bug by Ammler on the Redmine IRC.
In order to get Redmine to show Mercurial repositories, it is sometimes necessary to edit lib/redmine/scm/adapters/mercurial_adapter.rb as described here:
Apparently this is brittle, as lib/redmine/scm/adapters/mercurial_adapter.rb may be overwritten during Redmine upgrades.
In my own case, I've found that on Dreamhost, if I don't make the edit to lib/redmine/scm/adapters/mercurial_adapter.rb , then when I go to the "Repository" tab for my project in Redmine, I get an error that, "The entry or revision was not found in the repository."