When creating a Phabricator hosted repository, and trying to serve it over http (even for "Read only"), Phabricator warns that:
NOTE: The configuration setting diffusion.allow-http-auth is currently disabled. You must enable it to activate authenticated access to repositories over HTTP.
When going ahead nonetheless, and saving the changes, the repository status says:
Missing Binary git-http-backend Unable to find this binary in the webserver's PATH. You may need to configure environment.append-paths.