When using `rad init` the default branch for the project can be predetermined by
inspecting the working copy repository.
To improve the experience, it will first check `init.defaultBranch` in the Git
configuration file.
If it does not find this, it falls back to choosing the default head of the
repository at the time. This may be HEAD, and in this case it will error and
provide helpful information.
The repository may also not have any default head at the time, and this also
results in an error and hint.
Sekhat Temporus
Lorenz Leutgeb