comparison mercurial/changegroup.py @ 24977:4289383cb9d2

changegroup: document the cases where reordering complicates linkrevs

24976:147d8892fc4b

        for chunk in self.group(clnodes, cl, lookupcl, units=_('changesets')):
            size += len(chunk)
            yield chunk
        self._verbosenote(_('%8.i (changelog)\n') % size)

        fastpathlinkrev = fastpathlinkrev and not self._reorder
        # Callback for the manifest, used to collect linkrevs for filelog
        # revisions.
        # Returns the linkrev node (collected in lookupcl).
        def lookupmf(x):

24977:4289383cb9d2

        for chunk in self.group(clnodes, cl, lookupcl, units=_('changesets')):
            size += len(chunk)
            yield chunk
        self._verbosenote(_('%8.i (changelog)\n') % size)

        # We need to make sure that the linkrev in the changegroup refers to
        # the first changeset that introduced the manifest or file revision.
        # The fastpath is usually safer than the slowpath, because the filelogs
        # are walked in revlog order.
        #
        # When taking the slowpath with reorder=None and the manifest revlog
        # uses generaldelta, the manifest may be walked in the "wrong" order.
        # Without 'clrevorder', we would get an incorrect linkrev (see fix in
        # cc0ff93d0c0c).
        #
        # When taking the fastpath, we are only vulnerable to reordering
        # of the changelog itself. The changelog never uses generaldelta, so
        # it is only reordered when reorder=True. To handle this case, we
        # simply take the slowpath, which already has the 'clrevorder' logic.
        # This was also fixed in cc0ff93d0c0c.
        fastpathlinkrev = fastpathlinkrev and not self._reorder
        # Callback for the manifest, used to collect linkrevs for filelog
        # revisions.
        # Returns the linkrev node (collected in lookupcl).
        def lookupmf(x):