view tests/test-template-engine.t @ 36672:9e7b14caf67f

xdiff: remove patience and histogram diff algorithms

Patience diff is the normal diff algorithm, plus some greediness that
unconditionally matches common common unique lines.  That means it is easy to
construct cases to let it generate suboptimal result, like:

```
open('a', 'w').write('\n'.join(list('a' + 'x' * 300 + 'u' + 'x' * 700 + 'a\n')))
open('b', 'w').write('\n'.join(list('b' + 'x' * 700 + 'u' + 'x' * 300 + 'b\n')))
```

Patience diff has been advertised as being able to generate better results for
some C code changes. However, the more scientific way to do that is the
indention heuristic [1].

Since patience diff could generate suboptimal result more easily and its
"better" diff feature could be replaced by the new indention heuristic, let's
just remove it and its variant histogram diff to simplify the code.

[1]: https://github.com/git/git/commit/433860f3d0beb0c6f205290bd16cda413148f098

Test Plan:
`gcc -fPIC *.c --shared -o xdiff.so` still builds.

Differential Revision: https://phab.mercurial-scm.org/D2573

  $ cat > engine.py << EOF
  > 
  > from mercurial import templater
  > 
  > class mytemplater(object):
  >     def __init__(self, loader, filters, defaults, resources, aliases):
  >         self.loader = loader
  >         self._defaults = defaults
  >         self._resources = resources
  > 
  >     def symbol(self, mapping, key):
  >         return mapping[key]
  > 
  >     def resource(self, mapping, key):
  >         v = self._resources[key]
  >         if v is None:
  >             v = mapping[key]
  >         return v
  > 
  >     def process(self, t, map):
  >         tmpl = self.loader(t)
  >         props = self._defaults.copy()
  >         props.update(map)
  >         for k, v in props.items():
  >             if k in ('templ', 'ctx', 'repo', 'revcache', 'cache', 'troubles'):
  >                 continue
  >             if callable(v) and getattr(v, '_requires', None) is None:
  >                 props = self._resources.copy()
  >                 props.update(map)
  >                 v = v(**props)
  >             elif callable(v):
  >                 v = v(self, props)
  >             v = templater.stringify(v)
  >             tmpl = tmpl.replace('{{%s}}' % k, v)
  >         yield tmpl
  > 
  > templater.engines['my'] = mytemplater
  > EOF
  $ hg init test
  $ echo '[extensions]' > test/.hg/hgrc
  $ echo "engine = `pwd`/engine.py" >> test/.hg/hgrc
  $ cd test
  $ cat > mymap << EOF
  > changeset = my:changeset.txt
  > EOF
  $ cat > changeset.txt << EOF
  > {{rev}} {{node}} {{author}}
  > EOF
  $ hg ci -Ama
  adding changeset.txt
  adding mymap
  $ hg log --style=./mymap
  0 97e5f848f0936960273bbf75be6388cd0350a32b test

  $ cat > changeset.txt << EOF
  > {{p1rev}} {{p1node}} {{p2rev}} {{p2node}}
  > EOF
  $ hg ci -Ama
  $ hg log --style=./mymap
  0 97e5f848f0936960273bbf75be6388cd0350a32b -1 0000000000000000000000000000000000000000
  -1 0000000000000000000000000000000000000000 -1 0000000000000000000000000000000000000000

invalid engine type:

  $ echo 'changeset = unknown:changeset.txt' > unknownenginemap
  $ hg log --style=./unknownenginemap
  abort: invalid template engine: unknown
  [255]

  $ cd ..