there should be just one setting for default format

[Martin Pool]

At the moment BranchFormat (and Repository and WorkingTree, I think) have a concept of a default format, and there is also a default BzrDirFormat which implicitly sets them. If they are not in sync, wierd things may happen, at least in the test case. It might be better to have just one place where the default is set.

See also bug 90302.

[Robert Collins (lifeless)]

fixed for repositories in bzr.dev

[John A Meinel (jameinel)]

Looking at the code, all of the registries at least have the concept of a default. Most code paths just use the default metadir.

Robert fixed this for repositories by making the definition a bit circular:
RepositoryFormat:
    @classmethod
    def get_default_format(klass):
        """Return the current default format."""
        from bzrlib import bzrdir
        return bzrdir.format_registry.make_bzrdir('default').repository_format

And
BzrDirMetaFormat1:
    def __return_repository_format(self):
        """Circular import protection."""
        if getattr(self, '_repository_format', None):
            return self._repository_format
        from bzrlib.repository import RepositoryFormat
        return RepositoryFormat.get_default_format()

    def __set_repository_format(self, value):
        """Allow changing the repository format for metadir formats."""
        self._repository_format = value

    repository_format = property(__return_repository_format, __set_repository_format)

There is also
BzrDirFormatRegistry:
    def set_default_repository(self, key):
        """Set the FormatRegistry default and Repository default.

        This is a transitional method while Repository.set_default_format
        is deprecated.
        """
        if 'default' in self:
            self.remove('default')
        self.set_default(key)
        format = self.get('default')()

^- This is a bit confusing to me, since 'key' here should be talking about a repository (by the function name) but would have to be describing a bzrdir format, since it is setting self.set_default(key). Also, is the last line just to ensure that the format was properly registered?