tests/test-mdiff.py

revlog: move censor logic out of censor extension

The censor extension is doing very low-level things with revlogs.
It is fundamentally impossible for this logic to remain in the censor
extension while support multiple storage backends: we need each
storage backend to implement censor in its own storage-specific
way.

This commit effectively moves the revlog-specific censoring code to
be a method of revlogs themselves.

We've defined a new API on the file storage interface for censoring
an individual node. Even though the current censoring code doesn't
use it, the API requires a transaction instance because it logically
makes sense for storage backends to require an active transaction
(which implies a held write lock) in order to rewrite storage.

After this commit, the censor extension has been reduced to
boilerplate precondition checking before invoking the generic
storage API.

I tried to keep the code as similar as possible. But some minor
changes were made:

* We use self._io instead of instantiating a new revlogio instance.
* We compare self.version against REVLOGV0 instead of != REVLOGV1
  because presumably all future revlog versions will support censoring.
* We use self.opener instead of going through repo.svfs (we don't have
  a handle on the repo instance from a revlog).
* "revlog" dropped
* Replace "flog" with "self".

Differential Revision: https://phab.mercurial-scm.org/D4656

from __future__ import absolute_import
from __future__ import print_function

import unittest

from mercurial import (
    mdiff,
)

class splitnewlinesTests(unittest.TestCase):

    def test_splitnewlines(self):
        cases = {b'a\nb\nc\n': [b'a\n', b'b\n', b'c\n'],
                 b'a\nb\nc': [b'a\n', b'b\n', b'c'],
                 b'a\nb\nc\n\n': [b'a\n', b'b\n', b'c\n', b'\n'],
                 b'': [],
                 b'abcabc': [b'abcabc'],
                 }
        for inp, want in cases.items():
            self.assertEqual(mdiff.splitnewlines(inp), want)

if __name__ == '__main__':
    import silenttestrunner
    silenttestrunner.main(__name__)