Forge.mil is a mess -- and will probably always be a mess until they ditch Collabnet's SourceForge Enterprise Edition as a platform.

There is code out there that would transform GitLab's Open source edition to use PKI for authentication (I wrote it for an employer and threw it on, ironically enough, github), but, the DOD is set in its ways and I'm sure that CollabNet (and Steel Thread) is trying to milk that contract twenty ways from Sunday.