mercurial/state.py

copies: don't include copies that are not in source in directory move

I've been working on a rewrite of mergecopies(). I compared the output
of the rewritten version with the current version. I noticed that
between FIREFOX_NIGHTLY_59_END and FIREFOX_BETA_60_BASE in the
mozilla-unified repo, there were many copies that the current version
detected that the rewritten version did not. One example was
js/src/gc/Iteration.h -> js/src/gc/PublicIterators.h. Then I realized
that js/src/gc/Iteration.h doesn't even exist in
FIREFOX_NIGHTLY_59_END.

This patch adds a filtering step for the "fullcopy" dict. It turns out
that that change also affects the test for issue5020 in
test-merge-criss-cross.t. The 'dm' action no longer happens there. At
first I thought that the test case change meant that this patch was
broken, but I think it's actually correct tha the 'dm' action should
not happen there. The result of the bid merge is still the same.

I suspect this filtering is a better solution for the issue than
41f6af50c0d8 (merge: fix crash on criss cross merge with dir move and
delete (issue5020), 2017-01-31). I also suspect that it was broken
just a few months earlier by a005c33d0bd7 (mergecopies: add logic to
process incomplete data, 2016-10-04). Note that bid merge had been
enabled for a few years at that point, since 19903277f035 (merge: use
bid merge by default (BC), 2014-10-01).

This patch is still just a workaround. It will be cleaned up soon
(with the rewrite of mergecopies()). But doing this in a separate
patch makes later patches easier to understand and gives a place to
explain why this is changing.

Differential Revision: https://phab.mercurial-scm.org/D6244

# state.py - writing and reading state files in Mercurial
#
# Copyright 2018 Pulkit Goyal <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""
This file contains class to wrap the state for commands and other
related logic.

All the data related to the command state is stored as dictionary in the object.
The class has methods using which the data can be stored to disk in a file under
.hg/ directory.

We store the data on disk in cbor, for which we use the CBOR format to encode
the data.
"""

from __future__ import absolute_import

from . import (
    error,
    util,
)
from .utils import (
    cborutil,
)

class cmdstate(object):
    """a wrapper class to store the state of commands like `rebase`, `graft`,
    `histedit`, `shelve` etc. Extensions can also use this to write state files.

    All the data for the state is stored in the form of key-value pairs in a
    dictionary.

    The class object can write all the data to a file in .hg/ directory and
    can populate the object data reading that file.

    Uses cbor to serialize and deserialize data while writing and reading from
    disk.
    """

    def __init__(self, repo, fname):
        """ repo is the repo object
        fname is the file name in which data should be stored in .hg directory
        """
        self._repo = repo
        self.fname = fname

    def read(self):
        """read the existing state file and return a dict of data stored"""
        return self._read()

    def save(self, version, data):
        """write all the state data stored to .hg/<filename> file

        we use third-party library cbor to serialize data to write in the file.
        """
        if not isinstance(version, int):
            raise error.ProgrammingError("version of state file should be"
                                         " an integer")

        with self._repo.vfs(self.fname, 'wb', atomictemp=True) as fp:
            fp.write('%d\n' % version)
            for chunk in cborutil.streamencode(data):
                fp.write(chunk)

    def _read(self):
        """reads the state file and returns a dictionary which contain
        data in the same format as it was before storing"""
        with self._repo.vfs(self.fname, 'rb') as fp:
            try:
                int(fp.readline())
            except ValueError:
                raise error.CorruptedState("unknown version of state file"
                                           " found")

            return cborutil.decodeall(fp.read())[0]

    def delete(self):
        """drop the state file if exists"""
        util.unlinkpath(self._repo.vfs.join(self.fname), ignoremissing=True)

    def exists(self):
        """check whether the state file exists or not"""
        return self._repo.vfs.exists(self.fname)