It is strange, because create_new_release will call create_internal_release
from the PATH, and the current branch is not in the PATH. But I need that
to test the new way of creating CGAL releases using CMake.
My script
Maintenance/infrastructure/cgal.geometryfactory.com/bin/create_release
already fetch and reset the SCM (to precompile manual tools). No need have
create_release to it again.
Now I use `git rev-parse --abbrev-rev HEAD` to get the branch name, and
then `git reset --hard` to force the update to the last revision of the
branch.