comparison mercurial/repair.py @ 30775:513d68a90398

repair: implement requirements checking for upgrades

This commit introduces functionality for upgrading a repository in
place. The first part that's implemented is testing for upgrade
"compatibility." This is done by examining repository requirements.

There are 5 functions returning sets of requirements that control
upgrading. Why so many functions? Mainly to support extensions.
Functions are easier to monkeypatch than module variables.

Astute readers will see that we don't support "manifestv2" and
"treemanifest" requirements in the upgrade mechanism. I don't have
a great answer for why other than this is a complex set of patches
and I don't want to deal with the complexity of these experimental
features just yet. We can teach the upgrade mechanism about them
later, once the basic upgrade mechanism is in place.

This commit also introduces the "upgraderepo" function. This will be
our main routine for performing an in-place upgrade. Currently, it
just implements requirements checking. The structure of some code in
this function may look a bit weird (e.g. the inline function that is
only called once). But this will make sense after future commits.

30774:eaa5607132a2

    newobsstorefile = obsstore.svfs('obsstore', 'w', atomictemp=True)
    for bytes in obsolete.encodemarkers(left, True, obsstore._version):
        newobsstorefile.write(bytes)
    newobsstorefile.close()
    return n

30775:513d68a90398

    newobsstorefile = obsstore.svfs('obsstore', 'w', atomictemp=True)
    for bytes in obsolete.encodemarkers(left, True, obsstore._version):
        newobsstorefile.write(bytes)
    newobsstorefile.close()
    return n

def upgraderequiredsourcerequirements(repo):
    """Obtain requirements required to be present to upgrade a repo.

    An upgrade will not be allowed if the repository doesn't have the
    requirements returned by this function.
    """
    return set([
        # Introduced in Mercurial 0.9.2.
        'revlogv1',
        # Introduced in Mercurial 0.9.2.
        'store',
    ])

def upgradeblocksourcerequirements(repo):
    """Obtain requirements that will prevent an upgrade from occurring.

    An upgrade cannot be performed if the source repository contains a
    requirements in the returned set.
    """
    return set([
        # The upgrade code does not yet support these experimental features.
        # This is an artificial limitation.
        'manifestv2',
        'treemanifest',
        # This was a precursor to generaldelta and was never enabled by default.
        # It should (hopefully) not exist in the wild.
        'parentdelta',
        # Upgrade should operate on the actual store, not the shared link.
        'shared',
    ])

def upgradesupportremovedrequirements(repo):
    """Obtain requirements that can be removed during an upgrade.

    If an upgrade were to create a repository that dropped a requirement,
    the dropped requirement must appear in the returned set for the upgrade
    to be allowed.
    """
    return set()

def upgradesupporteddestrequirements(repo):
    """Obtain requirements that upgrade supports in the destination.

    If the result of the upgrade would create requirements not in this set,
    the upgrade is disallowed.

    Extensions should monkeypatch this to add their custom requirements.
    """
    return set([
        'dotencode',
        'fncache',
        'generaldelta',
        'revlogv1',
        'store',
    ])

def upgradeallowednewrequirements(repo):
    """Obtain requirements that can be added to a repository during upgrade.

    This is used to disallow proposed requirements from being added when
    they weren't present before.

    We use a list of allowed requirement additions instead of a list of known
    bad additions because the whitelist approach is safer and will prevent
    future, unknown requirements from accidentally being added.
    """
    return set([
        'dotencode',
        'fncache',
        'generaldelta',
    ])

def upgraderepo(ui, repo, run=False, optimize=None):
    """Upgrade a repository in place."""
    # Avoid cycle: cmdutil -> repair -> localrepo -> cmdutil
    from . import localrepo

    repo = repo.unfiltered()

    # Ensure the repository can be upgraded.
    missingreqs = upgraderequiredsourcerequirements(repo) - repo.requirements
    if missingreqs:
        raise error.Abort(_('cannot upgrade repository; requirement '
                            'missing: %s') % _(', ').join(sorted(missingreqs)))

    blockedreqs = upgradeblocksourcerequirements(repo) & repo.requirements
    if blockedreqs:
        raise error.Abort(_('cannot upgrade repository; unsupported source '
                            'requirement: %s') %
                          _(', ').join(sorted(blockedreqs)))

    # FUTURE there is potentially a need to control the wanted requirements via
    # command arguments or via an extension hook point.
    newreqs = localrepo.newreporequirements(repo)

    noremovereqs = (repo.requirements - newreqs -
                   upgradesupportremovedrequirements(repo))
    if noremovereqs:
        raise error.Abort(_('cannot upgrade repository; requirement would be '
                            'removed: %s') % _(', ').join(sorted(noremovereqs)))

    noaddreqs = (newreqs - repo.requirements -
                 upgradeallowednewrequirements(repo))
    if noaddreqs:
        raise error.Abort(_('cannot upgrade repository; do not support adding '
                            'requirement: %s') %
                          _(', ').join(sorted(noaddreqs)))

    unsupportedreqs = newreqs - upgradesupporteddestrequirements(repo)
    if unsupportedreqs:
        raise error.Abort(_('cannot upgrade repository; do not support '
                            'destination requirement: %s') %
                          _(', ').join(sorted(unsupportedreqs)))

    def printrequirements():
        ui.write(_('requirements\n'))
        ui.write(_('   preserved: %s\n') %
                 _(', ').join(sorted(newreqs & repo.requirements)))

        if repo.requirements - newreqs:
            ui.write(_('   removed: %s\n') %
                     _(', ').join(sorted(repo.requirements - newreqs)))

        if newreqs - repo.requirements:
            ui.write(_('   added: %s\n') %
                     _(', ').join(sorted(newreqs - repo.requirements)))

        ui.write('\n')

    if not run:
        ui.write(_('performing an upgrade with "--run" will make the following '
                   'changes:\n\n'))

        printrequirements()