GitVersionTasks throws ArgumentNullException when building on TeamCity.

[GeirGrusom]

Error occurred: System.ArgumentNullException: Value cannot be null.
Parameter name: path
at System.IO.Directory.GetParent(String path)
at GitVersion.ConfigurationProvider.GetConfigFilePath(String gitDirectory) in c:\BuildAgent\work\5106452ed7682238\GitVersionCore\Configuration\ConfigurationProvider.cs:line 56
at GitVersion.ConfigurationProvider.Provide(String gitDirectory, IFileSystem fileSystem) in c:\BuildAgent\work\5106452ed7682238\GitVersionCore\Configuration\ConfigurationProvider.cs:line 11
at GitVersionTask.WriteVersionInfoToBuildLog.InnerExecute() in c:\BuildAgent\work\5106452ed7682238\GitVersionTask\WriteVersionInfoToBuildLog.cs:line 53
at GitVersionTask.WriteVersionInfoToBuildLog.Execute() in c:\BuildAgent\work\5106452ed7682238\GitVersionTask\WriteVersionInfoToBuildLog.cs:line 31

Project using GitFlow. Builds fine locally, but fails on TeamCity. It seems that SolutionDirectory is null.
I have done no configuration other than installing the NuGet pacakge and removing AssemblyInfoAttributes.

Server is building using Microsoft Build Tools 2013.

[GeirGrusom]

It seems that the cause is that the build agent doesn't actually check out sources, but rather gets the repository, excluding the .git folder.

The obvious fix would be to check out sources on the build-agent.

edit: removed irrelevant info