$ hg init
  $ echo a > a
  $ hg ci -Am0
  adding a
  $ hg mv a b
  $ echo b >> b

Comment out this line to make this test succeed:

  $ python -c 'open("b", "a").write("\0")'
  $ hg ci -m1
  $ hg export -g tip > b.patch

Try to apply our patch:

  $ hg co 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg import --no-commit b.patch
  applying b.patch
  file b already exists
  1 out of 1 hunks FAILED -- saving rejects to file b.rej
  abort: patch failed to apply
  [255]
  $ hg st
  A b
  R a
  ? b.patch
  ? b.rej