Just been having to use Mecurial to get the Orchard source code.
I first used TortoiseHg to get the source and then used the Update command to switch to 1.x "branch" but I'd always get this error.
abort: path 'src\Orchard.Web\Modules\Orchard.Alias\AdminMenu.cs' is inside nested repo 'src\\Orchard.Web\\Modules\\Orchard.Alias'
So after a few attempts, all I did was delete everything apart from the .hg folder and then tried to update, this managed to work.
Who knows if this is the "correct" way to fix it.