Fixing tests for Linux

[fleimeris]

Most of the tests fail on Linux because of the hardcoded path in filling the repo:

SharpBucket/SharpBucketTests/GitHelpers/TestRepositoryBuilder.cs

Lines 111 to 114 in 96d068c

	Directory.CreateDirectory($"{WorkingDirectory}\\{dir}");
	}
	File.WriteAllText($"{WorkingDirectory}\\{fileName}", fileContent);
	Commands.Stage(repository, fileName);

Path.Combine will make it cross platform.