keyword: use parent of working copy as base for status

Instead of calling repo[None].status(), use the more common form that
uses the parent of the working copy as the base:
repo['.'].status(). Note that the former defaults to comparing to
revision '.', while the latter defaults to revision None, so the
contexts being compared are the same.

It might seem like this would result in a reverse diff, but it turns
out that workingctx.status() incorrectly reverses the result. That bug
will be fixed in a later commit.

hgext/keyword.py

@@ -619,7 +619,7 b' def reposetup(ui, repo):'
                 ret = super(kwrepo, self).rollback(dryrun, force)
                 if not dryrun:
                     ctx = self['.']
-                    modified, added = _preselect(self[None].status(), changed)
+                    modified, added = _preselect(ctx.status(), changed)
                     kwt.overwrite(ctx, modified, True, True)
                     kwt.overwrite(ctx, added, True, False)
                 return ret
@@ -702,7 +702,7 b' def reposetup(ui, repo):'
             # therefore compare nodes before and after
             kwt.postcommit = True
             ctx = repo['.']
-            wstatus = repo[None].status()
+            wstatus = ctx.status()
             ret = orig(ui, repo, commitfunc, *pats, **opts)
             recctx = repo['.']
             if ctx != recctx: