dirstate: drop workaround for '.' matching root directory The check was added in 31abcae33b4f (dirstate: do not ignore current directory '.' (issue 1078), 2008-04-05) to fix issue1078. Funnily enough, comment #2 on that issue mentions using '' instead of '.' to represent the root directory, just like my previous patch did. test-hgignore.t fails with this patch without the previous patch. Differential Revision: https://phab.mercurial-scm.org/D6402