tests/test-diff-newlines.t

streamclone: abort when client needs to handle obsmarkers, but doesn't

When client doesn't have any of obsolescence markers exchange capabilities,
then it's safe to say it can't handle obsmarkers. However, if it understands
even one format version, then stream clones are fine -- client can use
"obsmarkers" bundle2 part.

  $ 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