This commit adds the local changes handling behavior for branch checkout.
One of three can be selected: stash and reapply after checkout, discard changes or leave them as is (previous behaviour)
* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.
