tests/test-fastannotate-diffopts.t

dirstate-item: make sure we load `mtime-second-ambiguous` from disk

Now that we support the associated logic, we can safely load it from it. It is
no longer necessary to ignore the stored mtime when the flag is encountered.

Differential Revision: https://phab.mercurial-scm.org/D11846

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > fastannotate=
  > EOF

  $ hg init repo
  $ cd repo

changes to whitespaces

  $ cat >> a << EOF
  > 1
  > 
  >  
  >  2
  > EOF
  $ hg commit -qAm '1'
  $ cat > a << EOF
  >  1
  > 
  > 2
  > 
  > 
  > 3
  > EOF
  $ hg commit -m 2
  $ hg fastannotate -wB a
  0:  1
  0: 
  1: 2
  0: 
  1: 
  1: 3