revlog: always use a Rust index for REVLOGv1 if rustext is present We are about to change classes such as `rustext.AncestorsIterator` to take a Rust index, hence we cannot have the option not to use the Rust index. Note: this can be refined depending on whether we want to keep this option or not. We will have to make two versions of `AncestorsIterator` and its sibling to support REVLOGV2 and CHANGELOGv2 anyway. Meanwhile, this is the simplest change to make the tests pass.

  $ hg init repo
  $ cd repo

  $ "$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