Publish Documentation step report success but not publishing changes

Running locally I found that changes to documentation were staged however the `GitHasStagedChanges(publishFolder)` call on line 151 of wyam.cake returned false.
The step reported success, but did not push any documentation.

Start at line 151 of wyam.cake and inspect how GitHasStagedChanges(publishFolder) determines whether documentation changes are staged. Reproduce the local documentation publishing step, then verify that staged changes are detected and the step no longer reports success without publishing them.

Written by the indexing model from the issue text.