tests/test-diff-newlines.t

rust-dirstatemap: add `NonNormalEntries` class

This fix introduces the same encapsulation as the `copymap`. There is no easy
way of doing this any better for now.

`hg up -r null && time HGRCPATH= HGMODULEPOLICY=rust+c hg up tip` on Mozilla
Central, (not super recent, but it doesn't matter):

Before: 7:44,08 total
After: 1:03,23 total

Pretty brutal regression!

This is a graft on stable of cf1f8660e568

Differential Revision: https://phab.mercurial-scm.org/D8111

  $ hg init

  $ "$PYTHON" -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
  $ hg ci -Ama -d '1 0'
  adding a

  $ echo clean diff >> a
  $ hg ci -mb -d '2 0'

  $ hg diff -r0 -r1
  diff -r 107ba6f817b5 -r 310ce7989cdc a
  --- a/a	Thu Jan 01 00:00:01 1970 +0000
  +++ b/a	Thu Jan 01 00:00:02 1970 +0000
  @@ -1,2 +1,3 @@
   confuse str.splitlines
   embedded\r (no-eol) (esc)
  newline
  +clean diff