First, I tried this:
PS C:\code\chzbgr\Cheezburger\Cheezburger.Common\Database\Structure> hg kiln -a .\Importer.cs
cannot find .\Importer.cs
Hmm that didn't work, so next I tried from the repo's root:
PS C:\code\chzbgr\Cheezburger\Cheezburger.Common\Database\Structure> cd ..\..\..
PS C:\code\chzbgr\Cheezburger> hg kiln -a .\Cheezburger.Common\Database\Structure\Importer.cs
cannot find .\Cheezburger.Common\Database\Structure\Importer.cs
Nope, that didn't work. Maybe it was that ".\" at the beginning:
PS C:\code\chzbgr\Cheezburger> hg kiln -a Cheezburger.Common\Database\Structure\Importer.cs
cannot find Cheezburger.Common\Database\Structure\Importer.cs
Again no dice. Let's try forward slashes!
PS C:\code\chzbgr\Cheezburger> hg kiln -a Cheezburger.Common/Database/Structure/Importer.cs
That worked!?!?