tests/test-diff-antipatience.t

copies: detect case when a merge decision overwrite previous data

We now detect and record when a merge case required special logic (eg: thing
that append during the merge, ambiguity leading to picking p1 data, etc) and we
explicitly mark the result as superseding the previous data.

This fixes the family of test we previously added.

Differential Revision: https://phab.mercurial-scm.org/D9613

#testcases bdiff xdiff

#if xdiff
#require xdiff
  $ cat >> $HGRCPATH <<EOF
  > [experimental]
  > xdiff = true
  > EOF
#endif

Test case that makes use of the weakness of patience diff algorithm

  $ hg init
  >>> open('a', 'wb').write(('\n'.join(list('a' + 'x' * 10 + 'u' + 'x' * 30 + 'a\n'))).encode('ascii')) and None
  $ hg commit -m 1 -A a
  >>> open('a', 'wb').write(('\n'.join(list('b' + 'x' * 30 + 'u' + 'x' * 10 + 'b\n'))).encode('ascii')) and None
#if xdiff
  $ hg diff
  diff -r f0aeecb49805 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,4 +1,4 @@
  -a
  +b
   x
   x
   x
  @@ -9,7 +9,6 @@
   x
   x
   x
  -u
   x
   x
   x
  @@ -30,6 +29,7 @@
   x
   x
   x
  +u
   x
   x
   x
  @@ -40,5 +40,5 @@
   x
   x
   x
  -a
  +b
   
#else
  $ hg diff
  diff -r f0aeecb49805 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,15 +1,4 @@
  -a
  -x
  -x
  -x
  -x
  -x
  -x
  -x
  -x
  -x
  -x
  -u
  +b
   x
   x
   x
  @@ -40,5 +29,16 @@
   x
   x
   x
  -a
  +u
  +x
  +x
  +x
  +x
  +x
  +x
  +x
  +x
  +x
  +x
  +b
   
#endif