vfs: use 'vfs' module directly in 'mercurial.repair'

Now that the 'vfs' classes moved in their own module, lets use the new module
directly. We update code iteratively to help with possible bisect needs in the
future.

mercurial/repair.py

@@ -26,6 +26,7 b' from . import ('
     revlog,
     scmutil,
     util,
+    vfs as vfsmod,
 )
 
 def _bundle(repo, bases, heads, node, suffix, compress=True):
@@ -882,7 +883,7 b' def _upgraderepo(ui, srcrepo, dstrepo, r'
     ui.write(_('data fully migrated to temporary repository\n'))
 
     backuppath = tempfile.mkdtemp(prefix='upgradebackup.', dir=srcrepo.path)
-    backupvfs = scmutil.vfs(backuppath)
+    backupvfs = vfsmod.vfs(backuppath)
 
     # Make a backup of requires file first, as it is the first to be modified.
     util.copyfile(srcrepo.join('requires'), backupvfs.join('requires'))