view mercurial/filelog.py @ 39765:3e801ffd7269

filelog: custom filelog to be used with narrow repos

Narrow repos may have file revisions whose copy/rename metadata
references files not in the store. This can pose problems when
consumers attempt to access a missing referenced file revision.

The narrow extension hacks around this problem by implementing a
derived filelog type that provides custom implementations of
renamed(), size(), and cmp() which handle renames against files not
in the narrow spec by silently removing the rename metadata.

While silently dropping metadata isn't the most robust solution,
it is the easiest to implement.

This commit ports the custom narrow filelog class to core.

When a narrow repo is constructed, its ifilestorage creation
function will automatically use the new filelog type. This means
the extra logic is 0 cost for non-narrow repos and shouldn't
interfere with their operation.

Differential Revision: https://phab.mercurial-scm.org/D4643

# filelog.py - file history class for mercurial
#
# Copyright 2005-2007 Matt Mackall <[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.

from __future__ import absolute_import

from . import (
    error,
    repository,
    revlog,
)
from .utils import (
    interfaceutil,
)

@interfaceutil.implementer(repository.ifilestorage)
class filelog(object):
    def __init__(self, opener, path):
        self._revlog = revlog.revlog(opener,
                                     '/'.join(('data', path + '.i')),
                                     censorable=True)
        # full name of the user visible file, relative to the repository root
        self.filename = path
        self.index = self._revlog.index
        self.version = self._revlog.version
        self._generaldelta = self._revlog._generaldelta

    def __len__(self):
        return len(self._revlog)

    def __iter__(self):
        return self._revlog.__iter__()

    def revs(self, start=0, stop=None):
        return self._revlog.revs(start=start, stop=stop)

    def parents(self, node):
        return self._revlog.parents(node)

    def parentrevs(self, rev):
        return self._revlog.parentrevs(rev)

    def rev(self, node):
        return self._revlog.rev(node)

    def node(self, rev):
        return self._revlog.node(rev)

    def lookup(self, node):
        return self._revlog.lookup(node)

    def linkrev(self, rev):
        return self._revlog.linkrev(rev)

    def flags(self, rev):
        return self._revlog.flags(rev)

    def commonancestorsheads(self, node1, node2):
        return self._revlog.commonancestorsheads(node1, node2)

    def descendants(self, revs):
        return self._revlog.descendants(revs)

    def headrevs(self):
        return self._revlog.headrevs()

    def heads(self, start=None, stop=None):
        return self._revlog.heads(start, stop)

    def children(self, node):
        return self._revlog.children(node)

    def deltaparent(self, rev):
        return self._revlog.deltaparent(rev)

    def iscensored(self, rev):
        return self._revlog.iscensored(rev)

    def rawsize(self, rev):
        return self._revlog.rawsize(rev)

    def checkhash(self, text, node, p1=None, p2=None, rev=None):
        return self._revlog.checkhash(text, node, p1=p1, p2=p2, rev=rev)

    def revision(self, node, _df=None, raw=False):
        return self._revlog.revision(node, _df=_df, raw=raw)

    def revdiff(self, rev1, rev2):
        return self._revlog.revdiff(rev1, rev2)

    def emitrevisiondeltas(self, requests):
        return self._revlog.emitrevisiondeltas(requests)

    def addrevision(self, revisiondata, transaction, linkrev, p1, p2,
                    node=None, flags=revlog.REVIDX_DEFAULT_FLAGS,
                    cachedelta=None):
        return self._revlog.addrevision(revisiondata, transaction, linkrev,
                                    p1, p2, node=node, flags=flags,
                                    cachedelta=cachedelta)

    def addgroup(self, deltas, linkmapper, transaction, addrevisioncb=None):
        return self._revlog.addgroup(deltas, linkmapper, transaction,
                                 addrevisioncb=addrevisioncb)

    def getstrippoint(self, minlink):
        return self._revlog.getstrippoint(minlink)

    def strip(self, minlink, transaction):
        return self._revlog.strip(minlink, transaction)

    def files(self):
        return self._revlog.files()

    def checksize(self):
        return self._revlog.checksize()

    def read(self, node):
        t = self.revision(node)
        if not t.startswith('\1\n'):
            return t
        s = t.index('\1\n', 2)
        return t[s + 2:]

    def add(self, text, meta, transaction, link, p1=None, p2=None):
        if meta or text.startswith('\1\n'):
            text = revlog.packmeta(meta, text)
        return self.addrevision(text, transaction, link, p1, p2)

    def renamed(self, node):
        if self.parents(node)[0] != revlog.nullid:
            return False
        t = self.revision(node)
        m = revlog.parsemeta(t)[0]
        # copy and copyrev occur in pairs. In rare cases due to bugs,
        # one can occur without the other.
        if m and "copy" in m and "copyrev" in m:
            return (m["copy"], revlog.bin(m["copyrev"]))
        return False

    def size(self, rev):
        """return the size of a given revision"""

        # for revisions with renames, we have to go the slow way
        node = self.node(rev)
        if self.renamed(node):
            return len(self.read(node))
        if self.iscensored(rev):
            return 0

        # XXX if self.read(node).startswith("\1\n"), this returns (size+4)
        return self._revlog.size(rev)

    def cmp(self, node, text):
        """compare text with a given file revision

        returns True if text is different than what is stored.
        """

        t = text
        if text.startswith('\1\n'):
            t = '\1\n\1\n' + text

        samehashes = not self._revlog.cmp(node, t)
        if samehashes:
            return False

        # censored files compare against the empty file
        if self.iscensored(self.rev(node)):
            return text != ''

        # renaming a file produces a different hash, even if the data
        # remains unchanged. Check if it's the case (slow):
        if self.renamed(node):
            t2 = self.read(node)
            return t2 != text

        return True

    @property
    def filename(self):
        return self._revlog.filename

    @filename.setter
    def filename(self, value):
        self._revlog.filename = value

    # TODO these aren't part of the interface and aren't internal methods.
    # Callers should be fixed to not use them.
    @property
    def indexfile(self):
        return self._revlog.indexfile

    @indexfile.setter
    def indexfile(self, value):
        self._revlog.indexfile = value

    @property
    def datafile(self):
        return self._revlog.datafile

    @property
    def opener(self):
        return self._revlog.opener

    def clone(self, tr, destrevlog, **kwargs):
        if not isinstance(destrevlog, filelog):
            raise error.ProgrammingError('expected filelog to clone()')

        return self._revlog.clone(tr, destrevlog._revlog, **kwargs)

    def start(self, rev):
        return self._revlog.start(rev)

    def end(self, rev):
        return self._revlog.end(rev)

    def length(self, rev):
        return self._revlog.length(rev)

    def compress(self, data):
        return self._revlog.compress(data)

    def _addrevision(self, *args, **kwargs):
        return self._revlog._addrevision(*args, **kwargs)

class narrowfilelog(filelog):
    """Filelog variation to be used with narrow stores."""

    def __init__(self, opener, path, narrowmatch):
        super(narrowfilelog, self).__init__(opener, path)
        self._narrowmatch = narrowmatch

    def renamed(self, node):
        res = super(narrowfilelog, self).renamed(node)

        # Renames that come from outside the narrowspec are problematic
        # because we may lack the base text for the rename. This can result
        # in code attempting to walk the ancestry or compute a diff
        # encountering a missing revision. We address this by silently
        # removing rename metadata if the source file is outside the
        # narrow spec.
        #
        # A better solution would be to see if the base revision is available,
        # rather than assuming it isn't.
        #
        # An even better solution would be to teach all consumers of rename
        # metadata that the base revision may not be available.
        #
        # TODO consider better ways of doing this.
        if res and not self._narrowmatch(res[0]):
            return None

        return res

    def size(self, rev):
        # Because we have a custom renamed() that may lie, we need to call
        # the base renamed() to report accurate results.
        node = self.node(rev)
        if super(narrowfilelog, self).renamed(node):
            return len(self.read(node))
        else:
            return super(narrowfilelog, self).size(rev)

    def cmp(self, node, text):
        different = super(narrowfilelog, self).cmp(node, text)

        # Because renamed() may lie, we may get false positives for
        # different content. Check for this by comparing against the original
        # renamed() implementation.
        if different:
            if super(narrowfilelog, self).renamed(node):
                t2 = self.read(node)
                return t2 != text

        return different