Merge branch 'jc/no-default-attr-tree-in-bare'

Git 2.43 started using the tree of HEAD as the source of attributes in a bare repository, which has severe performance implications. For now, revert the change, without ripping out a more explicit support for the attr.tree configuration variable. * jc/no-default-attr-tree-in-bare: stop using HEAD for attributes in bare repository by default