I work at a company with a large number of repositories - around 300 - some of which are little-used. The vast majority are Git repos, but a couple are still in hg (especially some of the more obscure repos). Today, one of our engineers went to clone one of these little-used repos - navigating there by directly typing the repo slug into the URL, rather than through the Diffusion UI (because we have so many repos). He attempted to git clone it, and received an error message informing him:

fatal: '/phab_path/repos/<redacted>' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

After some minutes of attempting to figure out whether his git configuration was somehow messed up, or if he didn't have access rights, he came to our team, and fortunately someone knew offhand that this was an hg repository. (Otherwise, I'm sure we would have eventually noticed the .hgignore file in the base of the repo, but it's not the first place we looked.)

The root problem, as I see it, is that if an engineer attempts to use the wrong VCS on a repo, there is not an immediate and obvious way for them to realize the nature of their simple mistake. In this case, the engineer (and I) suspected a number of other things before we realized he was using the wrong VCS.

My proposed solution would be that we indicate in the "Details" view which VCS is in use. I know that the type is shown when browsing repositories, but it's easy to miss, especially if you directly navigate to the repository page URL.