view mercurial/wireproto.py @ 21653:4188cae727ce

wireproto: use pushkey.decodekey

# wireproto.py - generic wire protocol support functions
#
# Copyright 2005-2010 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.

import urllib, tempfile, os, sys
from i18n import _
from node import bin, hex
import changegroup as changegroupmod, bundle2, pushkey as pushkeymod
import peer, error, encoding, util, store, exchange


class abstractserverproto(object):
    """abstract class that summarizes the protocol API

    Used as reference and documentation.
    """

    def getargs(self, args):
        """return the value for arguments in <args>

        returns a list of values (same order as <args>)"""
        raise NotImplementedError()

    def getfile(self, fp):
        """write the whole content of a file into a file like object

        The file is in the form::

            (<chunk-size>\n<chunk>)+0\n

        chunk size is the ascii version of the int.
        """
        raise NotImplementedError()

    def redirect(self):
        """may setup interception for stdout and stderr

        See also the `restore` method."""
        raise NotImplementedError()

    # If the `redirect` function does install interception, the `restore`
    # function MUST be defined. If interception is not used, this function
    # MUST NOT be defined.
    #
    # left commented here on purpose
    #
    #def restore(self):
    #    """reinstall previous stdout and stderr and return intercepted stdout
    #    """
    #    raise NotImplementedError()

    def groupchunks(self, cg):
        """return 4096 chunks from a changegroup object

        Some protocols may have compressed the contents."""
        raise NotImplementedError()

# abstract batching support

class future(object):
    '''placeholder for a value to be set later'''
    def set(self, value):
        if util.safehasattr(self, 'value'):
            raise error.RepoError("future is already set")
        self.value = value

class batcher(object):
    '''base class for batches of commands submittable in a single request

    All methods invoked on instances of this class are simply queued and
    return a a future for the result. Once you call submit(), all the queued
    calls are performed and the results set in their respective futures.
    '''
    def __init__(self):
        self.calls = []
    def __getattr__(self, name):
        def call(*args, **opts):
            resref = future()
            self.calls.append((name, args, opts, resref,))
            return resref
        return call
    def submit(self):
        pass

class localbatch(batcher):
    '''performs the queued calls directly'''
    def __init__(self, local):
        batcher.__init__(self)
        self.local = local
    def submit(self):
        for name, args, opts, resref in self.calls:
            resref.set(getattr(self.local, name)(*args, **opts))

class remotebatch(batcher):
    '''batches the queued calls; uses as few roundtrips as possible'''
    def __init__(self, remote):
        '''remote must support _submitbatch(encbatch) and
        _submitone(op, encargs)'''
        batcher.__init__(self)
        self.remote = remote
    def submit(self):
        req, rsp = [], []
        for name, args, opts, resref in self.calls:
            mtd = getattr(self.remote, name)
            batchablefn = getattr(mtd, 'batchable', None)
            if batchablefn is not None:
                batchable = batchablefn(mtd.im_self, *args, **opts)
                encargsorres, encresref = batchable.next()
                if encresref:
                    req.append((name, encargsorres,))
                    rsp.append((batchable, encresref, resref,))
                else:
                    resref.set(encargsorres)
            else:
                if req:
                    self._submitreq(req, rsp)
                    req, rsp = [], []
                resref.set(mtd(*args, **opts))
        if req:
            self._submitreq(req, rsp)
    def _submitreq(self, req, rsp):
        encresults = self.remote._submitbatch(req)
        for encres, r in zip(encresults, rsp):
            batchable, encresref, resref = r
            encresref.set(encres)
            resref.set(batchable.next())

def batchable(f):
    '''annotation for batchable methods

    Such methods must implement a coroutine as follows:

    @batchable
    def sample(self, one, two=None):
        # Handle locally computable results first:
        if not one:
            yield "a local result", None
        # Build list of encoded arguments suitable for your wire protocol:
        encargs = [('one', encode(one),), ('two', encode(two),)]
        # Create future for injection of encoded result:
        encresref = future()
        # Return encoded arguments and future:
        yield encargs, encresref
        # Assuming the future to be filled with the result from the batched
        # request now. Decode it:
        yield decode(encresref.value)

    The decorator returns a function which wraps this coroutine as a plain
    method, but adds the original method as an attribute called "batchable",
    which is used by remotebatch to split the call into separate encoding and
    decoding phases.
    '''
    def plain(*args, **opts):
        batchable = f(*args, **opts)
        encargsorres, encresref = batchable.next()
        if not encresref:
            return encargsorres # a local result in this case
        self = args[0]
        encresref.set(self._submitone(f.func_name, encargsorres))
        return batchable.next()
    setattr(plain, 'batchable', f)
    return plain

# list of nodes encoding / decoding

def decodelist(l, sep=' '):
    if l:
        return map(bin, l.split(sep))
    return []

def encodelist(l, sep=' '):
    return sep.join(map(hex, l))

# batched call argument encoding

def escapearg(plain):
    return (plain
            .replace(':', '::')
            .replace(',', ':,')
            .replace(';', ':;')
            .replace('=', ':='))

def unescapearg(escaped):
    return (escaped
            .replace(':=', '=')
            .replace(':;', ';')
            .replace(':,', ',')
            .replace('::', ':'))

# mapping of options accepted by getbundle and their types
#
# Meant to be extended by extensions. It is extensions responsibility to ensure
# such options are properly processed in exchange.getbundle.
#
# supported types are:
#
# :nodes: list of binary nodes
# :csv:   list of comma-separated values
# :plain: string with no transformation needed.
gboptsmap = {'heads':  'nodes',
             'common': 'nodes',
             'bundlecaps': 'csv'}

# client side

class wirepeer(peer.peerrepository):

    def batch(self):
        return remotebatch(self)
    def _submitbatch(self, req):
        cmds = []
        for op, argsdict in req:
            args = ','.join('%s=%s' % p for p in argsdict.iteritems())
            cmds.append('%s %s' % (op, args))
        rsp = self._call("batch", cmds=';'.join(cmds))
        return rsp.split(';')
    def _submitone(self, op, args):
        return self._call(op, **args)

    @batchable
    def lookup(self, key):
        self.requirecap('lookup', _('look up remote revision'))
        f = future()
        yield {'key': encoding.fromlocal(key)}, f
        d = f.value
        success, data = d[:-1].split(" ", 1)
        if int(success):
            yield bin(data)
        self._abort(error.RepoError(data))

    @batchable
    def heads(self):
        f = future()
        yield {}, f
        d = f.value
        try:
            yield decodelist(d[:-1])
        except ValueError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    @batchable
    def known(self, nodes):
        f = future()
        yield {'nodes': encodelist(nodes)}, f
        d = f.value
        try:
            yield [bool(int(f)) for f in d]
        except ValueError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    @batchable
    def branchmap(self):
        f = future()
        yield {}, f
        d = f.value
        try:
            branchmap = {}
            for branchpart in d.splitlines():
                branchname, branchheads = branchpart.split(' ', 1)
                branchname = encoding.tolocal(urllib.unquote(branchname))
                branchheads = decodelist(branchheads)
                branchmap[branchname] = branchheads
            yield branchmap
        except TypeError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    def branches(self, nodes):
        n = encodelist(nodes)
        d = self._call("branches", nodes=n)
        try:
            br = [tuple(decodelist(b)) for b in d.splitlines()]
            return br
        except ValueError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    def between(self, pairs):
        batch = 8 # avoid giant requests
        r = []
        for i in xrange(0, len(pairs), batch):
            n = " ".join([encodelist(p, '-') for p in pairs[i:i + batch]])
            d = self._call("between", pairs=n)
            try:
                r.extend(l and decodelist(l) or [] for l in d.splitlines())
            except ValueError:
                self._abort(error.ResponseError(_("unexpected response:"), d))
        return r

    @batchable
    def pushkey(self, namespace, key, old, new):
        if not self.capable('pushkey'):
            yield False, None
        f = future()
        self.ui.debug('preparing pushkey for "%s:%s"\n' % (namespace, key))
        yield {'namespace': encoding.fromlocal(namespace),
               'key': encoding.fromlocal(key),
               'old': encoding.fromlocal(old),
               'new': encoding.fromlocal(new)}, f
        d = f.value
        d, output = d.split('\n', 1)
        try:
            d = bool(int(d))
        except ValueError:
            raise error.ResponseError(
                _('push failed (unexpected response):'), d)
        for l in output.splitlines(True):
            self.ui.status(_('remote: '), l)
        yield d

    @batchable
    def listkeys(self, namespace):
        if not self.capable('pushkey'):
            yield {}, None
        f = future()
        self.ui.debug('preparing listkeys for "%s"\n' % namespace)
        yield {'namespace': encoding.fromlocal(namespace)}, f
        d = f.value
        yield pushkeymod.decodekeys(d)

    def stream_out(self):
        return self._callstream('stream_out')

    def changegroup(self, nodes, kind):
        n = encodelist(nodes)
        f = self._callcompressable("changegroup", roots=n)
        return changegroupmod.unbundle10(f, 'UN')

    def changegroupsubset(self, bases, heads, kind):
        self.requirecap('changegroupsubset', _('look up remote changes'))
        bases = encodelist(bases)
        heads = encodelist(heads)
        f = self._callcompressable("changegroupsubset",
                                   bases=bases, heads=heads)
        return changegroupmod.unbundle10(f, 'UN')

    def getbundle(self, source, **kwargs):
        self.requirecap('getbundle', _('look up remote changes'))
        opts = {}
        for key, value in kwargs.iteritems():
            if value is None:
                continue
            keytype = gboptsmap.get(key)
            if keytype is None:
                assert False, 'unexpected'
            elif keytype == 'nodes':
                value = encodelist(value)
            elif keytype == 'csv':
                value = ','.join(value)
            elif keytype != 'plain':
                raise KeyError('unknown getbundle option type %s'
                               % keytype)
            opts[key] = value
        f = self._callcompressable("getbundle", **opts)
        bundlecaps = kwargs.get('bundlecaps')
        if bundlecaps is not None and 'HG2X' in bundlecaps:
            return bundle2.unbundle20(self.ui, f)
        else:
            return changegroupmod.unbundle10(f, 'UN')

    def unbundle(self, cg, heads, source):
        '''Send cg (a readable file-like object representing the
        changegroup to push, typically a chunkbuffer object) to the
        remote server as a bundle.

        When pushing a bundle10 stream, return an integer indicating the
        result of the push (see localrepository.addchangegroup()).

        When pushing a bundle20 stream, return a bundle20 stream.'''

        if heads != ['force'] and self.capable('unbundlehash'):
            heads = encodelist(['hashed',
                                util.sha1(''.join(sorted(heads))).digest()])
        else:
            heads = encodelist(heads)

        if util.safehasattr(cg, 'deltaheader'):
            # this a bundle10, do the old style call sequence
            ret, output = self._callpush("unbundle", cg, heads=heads)
            if ret == "":
                raise error.ResponseError(
                    _('push failed:'), output)
            try:
                ret = int(ret)
            except ValueError:
                raise error.ResponseError(
                    _('push failed (unexpected response):'), ret)

            for l in output.splitlines(True):
                self.ui.status(_('remote: '), l)
        else:
            # bundle2 push. Send a stream, fetch a stream.
            stream = self._calltwowaystream('unbundle', cg, heads=heads)
            ret = bundle2.unbundle20(self.ui, stream)
        return ret

    def debugwireargs(self, one, two, three=None, four=None, five=None):
        # don't pass optional arguments left at their default value
        opts = {}
        if three is not None:
            opts['three'] = three
        if four is not None:
            opts['four'] = four
        return self._call('debugwireargs', one=one, two=two, **opts)

    def _call(self, cmd, **args):
        """execute <cmd> on the server

        The command is expected to return a simple string.

        returns the server reply as a string."""
        raise NotImplementedError()

    def _callstream(self, cmd, **args):
        """execute <cmd> on the server

        The command is expected to return a stream.

        returns the server reply as a file like object."""
        raise NotImplementedError()

    def _callcompressable(self, cmd, **args):
        """execute <cmd> on the server

        The command is expected to return a stream.

        The stream may have been compressed in some implementations. This
        function takes care of the decompression. This is the only difference
        with _callstream.

        returns the server reply as a file like object.
        """
        raise NotImplementedError()

    def _callpush(self, cmd, fp, **args):
        """execute a <cmd> on server

        The command is expected to be related to a push. Push has a special
        return method.

        returns the server reply as a (ret, output) tuple. ret is either
        empty (error) or a stringified int.
        """
        raise NotImplementedError()

    def _calltwowaystream(self, cmd, fp, **args):
        """execute <cmd> on server

        The command will send a stream to the server and get a stream in reply.
        """
        raise NotImplementedError()

    def _abort(self, exception):
        """clearly abort the wire protocol connection and raise the exception
        """
        raise NotImplementedError()

# server side

# wire protocol command can either return a string or one of these classes.
class streamres(object):
    """wireproto reply: binary stream

    The call was successful and the result is a stream.
    Iterate on the `self.gen` attribute to retrieve chunks.
    """
    def __init__(self, gen):
        self.gen = gen

class pushres(object):
    """wireproto reply: success with simple integer return

    The call was successful and returned an integer contained in `self.res`.
    """
    def __init__(self, res):
        self.res = res

class pusherr(object):
    """wireproto reply: failure

    The call failed. The `self.res` attribute contains the error message.
    """
    def __init__(self, res):
        self.res = res

class ooberror(object):
    """wireproto reply: failure of a batch of operation

    Something failed during a batch call. The error message is stored in
    `self.message`.
    """
    def __init__(self, message):
        self.message = message

def dispatch(repo, proto, command):
    repo = repo.filtered("served")
    func, spec = commands[command]
    args = proto.getargs(spec)
    return func(repo, proto, *args)

def options(cmd, keys, others):
    opts = {}
    for k in keys:
        if k in others:
            opts[k] = others[k]
            del others[k]
    if others:
        sys.stderr.write("abort: %s got unexpected arguments %s\n"
                         % (cmd, ",".join(others)))
    return opts

# list of commands
commands = {}

def wireprotocommand(name, args=''):
    """decorator for wire protocol command"""
    def register(func):
        commands[name] = (func, args)
        return func
    return register

@wireprotocommand('batch', 'cmds *')
def batch(repo, proto, cmds, others):
    repo = repo.filtered("served")
    res = []
    for pair in cmds.split(';'):
        op, args = pair.split(' ', 1)
        vals = {}
        for a in args.split(','):
            if a:
                n, v = a.split('=')
                vals[n] = unescapearg(v)
        func, spec = commands[op]
        if spec:
            keys = spec.split()
            data = {}
            for k in keys:
                if k == '*':
                    star = {}
                    for key in vals.keys():
                        if key not in keys:
                            star[key] = vals[key]
                    data['*'] = star
                else:
                    data[k] = vals[k]
            result = func(repo, proto, *[data[k] for k in keys])
        else:
            result = func(repo, proto)
        if isinstance(result, ooberror):
            return result
        res.append(escapearg(result))
    return ';'.join(res)

@wireprotocommand('between', 'pairs')
def between(repo, proto, pairs):
    pairs = [decodelist(p, '-') for p in pairs.split(" ")]
    r = []
    for b in repo.between(pairs):
        r.append(encodelist(b) + "\n")
    return "".join(r)

@wireprotocommand('branchmap')
def branchmap(repo, proto):
    branchmap = repo.branchmap()
    heads = []
    for branch, nodes in branchmap.iteritems():
        branchname = urllib.quote(encoding.fromlocal(branch))
        branchnodes = encodelist(nodes)
        heads.append('%s %s' % (branchname, branchnodes))
    return '\n'.join(heads)

@wireprotocommand('branches', 'nodes')
def branches(repo, proto, nodes):
    nodes = decodelist(nodes)
    r = []
    for b in repo.branches(nodes):
        r.append(encodelist(b) + "\n")
    return "".join(r)


wireprotocaps = ['lookup', 'changegroupsubset', 'branchmap', 'pushkey',
                 'known', 'getbundle', 'unbundlehash', 'batch']

def _capabilities(repo, proto):
    """return a list of capabilities for a repo

    This function exists to allow extensions to easily wrap capabilities
    computation

    - returns a lists: easy to alter
    - change done here will be propagated to both `capabilities` and `hello`
      command without any other action needed.
    """
    # copy to prevent modification of the global list
    caps = list(wireprotocaps)
    if _allowstream(repo.ui):
        if repo.ui.configbool('server', 'preferuncompressed', False):
            caps.append('stream-preferred')
        requiredformats = repo.requirements & repo.supportedformats
        # if our local revlogs are just revlogv1, add 'stream' cap
        if not requiredformats - set(('revlogv1',)):
            caps.append('stream')
        # otherwise, add 'streamreqs' detailing our local revlog format
        else:
            caps.append('streamreqs=%s' % ','.join(requiredformats))
    if repo.ui.configbool('experimental', 'bundle2-exp', False):
        capsblob = bundle2.encodecaps(repo.bundle2caps)
        caps.append('bundle2-exp=' + urllib.quote(capsblob))
    caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
    caps.append('httpheader=1024')
    return caps

# If you are writing an extension and consider wrapping this function. Wrap
# `_capabilities` instead.
@wireprotocommand('capabilities')
def capabilities(repo, proto):
    return ' '.join(_capabilities(repo, proto))

@wireprotocommand('changegroup', 'roots')
def changegroup(repo, proto, roots):
    nodes = decodelist(roots)
    cg = changegroupmod.changegroup(repo, nodes, 'serve')
    return streamres(proto.groupchunks(cg))

@wireprotocommand('changegroupsubset', 'bases heads')
def changegroupsubset(repo, proto, bases, heads):
    bases = decodelist(bases)
    heads = decodelist(heads)
    cg = changegroupmod.changegroupsubset(repo, bases, heads, 'serve')
    return streamres(proto.groupchunks(cg))

@wireprotocommand('debugwireargs', 'one two *')
def debugwireargs(repo, proto, one, two, others):
    # only accept optional args from the known set
    opts = options('debugwireargs', ['three', 'four'], others)
    return repo.debugwireargs(one, two, **opts)

# List of options accepted by getbundle.
#
# Meant to be extended by extensions. It is the extension's responsibility to
# ensure such options are properly processed in exchange.getbundle.
gboptslist = ['heads', 'common', 'bundlecaps']

@wireprotocommand('getbundle', '*')
def getbundle(repo, proto, others):
    opts = options('getbundle', gboptsmap.keys(), others)
    for k, v in opts.iteritems():
        keytype = gboptsmap[k]
        if keytype == 'nodes':
            opts[k] = decodelist(v)
        elif keytype == 'csv':
            opts[k] = set(v.split(','))
        elif keytype != 'plain':
            raise KeyError('unknown getbundle option type %s'
                           % keytype)
    cg = exchange.getbundle(repo, 'serve', **opts)
    return streamres(proto.groupchunks(cg))

@wireprotocommand('heads')
def heads(repo, proto):
    h = repo.heads()
    return encodelist(h) + "\n"

@wireprotocommand('hello')
def hello(repo, proto):
    '''the hello command returns a set of lines describing various
    interesting things about the server, in an RFC822-like format.
    Currently the only one defined is "capabilities", which
    consists of a line in the form:

    capabilities: space separated list of tokens
    '''
    return "capabilities: %s\n" % (capabilities(repo, proto))

@wireprotocommand('listkeys', 'namespace')
def listkeys(repo, proto, namespace):
    d = repo.listkeys(encoding.tolocal(namespace)).items()
    return pushkeymod.encodekeys(d)

@wireprotocommand('lookup', 'key')
def lookup(repo, proto, key):
    try:
        k = encoding.tolocal(key)
        c = repo[k]
        r = c.hex()
        success = 1
    except Exception, inst:
        r = str(inst)
        success = 0
    return "%s %s\n" % (success, r)

@wireprotocommand('known', 'nodes *')
def known(repo, proto, nodes, others):
    return ''.join(b and "1" or "0" for b in repo.known(decodelist(nodes)))

@wireprotocommand('pushkey', 'namespace key old new')
def pushkey(repo, proto, namespace, key, old, new):
    # compatibility with pre-1.8 clients which were accidentally
    # sending raw binary nodes rather than utf-8-encoded hex
    if len(new) == 20 and new.encode('string-escape') != new:
        # looks like it could be a binary node
        try:
            new.decode('utf-8')
            new = encoding.tolocal(new) # but cleanly decodes as UTF-8
        except UnicodeDecodeError:
            pass # binary, leave unmodified
    else:
        new = encoding.tolocal(new) # normal path

    if util.safehasattr(proto, 'restore'):

        proto.redirect()

        try:
            r = repo.pushkey(encoding.tolocal(namespace), encoding.tolocal(key),
                             encoding.tolocal(old), new) or False
        except util.Abort:
            r = False

        output = proto.restore()

        return '%s\n%s' % (int(r), output)

    r = repo.pushkey(encoding.tolocal(namespace), encoding.tolocal(key),
                     encoding.tolocal(old), new)
    return '%s\n' % int(r)

def _allowstream(ui):
    return ui.configbool('server', 'uncompressed', True, untrusted=True)

def _walkstreamfiles(repo):
    # this is it's own function so extensions can override it
    return repo.store.walk()

@wireprotocommand('stream_out')
def stream(repo, proto):
    '''If the server supports streaming clone, it advertises the "stream"
    capability with a value representing the version and flags of the repo
    it is serving. Client checks to see if it understands the format.

    The format is simple: the server writes out a line with the amount
    of files, then the total amount of bytes to be transferred (separated
    by a space). Then, for each file, the server first writes the filename
    and file size (separated by the null character), then the file contents.
    '''

    if not _allowstream(repo.ui):
        return '1\n'

    entries = []
    total_bytes = 0
    try:
        # get consistent snapshot of repo, lock during scan
        lock = repo.lock()
        try:
            repo.ui.debug('scanning\n')
            for name, ename, size in _walkstreamfiles(repo):
                if size:
                    entries.append((name, size))
                    total_bytes += size
        finally:
            lock.release()
    except error.LockError:
        return '2\n' # error: 2

    def streamer(repo, entries, total):
        '''stream out all metadata files in repository.'''
        yield '0\n' # success
        repo.ui.debug('%d files, %d bytes to transfer\n' %
                      (len(entries), total_bytes))
        yield '%d %d\n' % (len(entries), total_bytes)

        sopener = repo.sopener
        oldaudit = sopener.mustaudit
        debugflag = repo.ui.debugflag
        sopener.mustaudit = False

        try:
            for name, size in entries:
                if debugflag:
                    repo.ui.debug('sending %s (%d bytes)\n' % (name, size))
                # partially encode name over the wire for backwards compat
                yield '%s\0%d\n' % (store.encodedir(name), size)
                if size <= 65536:
                    fp = sopener(name)
                    try:
                        data = fp.read(size)
                    finally:
                        fp.close()
                    yield data
                else:
                    for chunk in util.filechunkiter(sopener(name), limit=size):
                        yield chunk
        # replace with "finally:" when support for python 2.4 has been dropped
        except Exception:
            sopener.mustaudit = oldaudit
            raise
        sopener.mustaudit = oldaudit

    return streamres(streamer(repo, entries, total_bytes))

@wireprotocommand('unbundle', 'heads')
def unbundle(repo, proto, heads):
    their_heads = decodelist(heads)

    try:
        proto.redirect()

        exchange.check_heads(repo, their_heads, 'preparing changes')

        # write bundle data to temporary file because it can be big
        fd, tempname = tempfile.mkstemp(prefix='hg-unbundle-')
        fp = os.fdopen(fd, 'wb+')
        r = 0
        try:
            proto.getfile(fp)
            fp.seek(0)
            gen = exchange.readbundle(repo.ui, fp, None)
            r = exchange.unbundle(repo, gen, their_heads, 'serve',
                                  proto._client())
            if util.safehasattr(r, 'addpart'):
                # The return looks streameable, we are in the bundle2 case and
                # should return a stream.
                return streamres(r.getchunks())
            return pushres(r)

        finally:
            fp.close()
            os.unlink(tempname)
    except error.BundleValueError, exc:
            bundler = bundle2.bundle20(repo.ui)
            errpart = bundler.newpart('B2X:ERROR:UNSUPPORTEDCONTENT')
            if exc.parttype is not None:
                errpart.addparam('parttype', exc.parttype)
            if exc.params:
                errpart.addparam('params', '\0'.join(exc.params))
            return streamres(bundler.getchunks())
    except util.Abort, inst:
        # The old code we moved used sys.stderr directly.
        # We did not change it to minimise code change.
        # This need to be moved to something proper.
        # Feel free to do it.
        if getattr(inst, 'duringunbundle2', False):
            bundler = bundle2.bundle20(repo.ui)
            manargs = [('message', str(inst))]
            advargs = []
            if inst.hint is not None:
                advargs.append(('hint', inst.hint))
            bundler.addpart(bundle2.bundlepart('B2X:ERROR:ABORT',
                                               manargs, advargs))
            return streamres(bundler.getchunks())
        else:
            sys.stderr.write("abort: %s\n" % inst)
            return pushres(0)
    except error.PushRaced, exc:
        if getattr(exc, 'duringunbundle2', False):
            bundler = bundle2.bundle20(repo.ui)
            bundler.newpart('B2X:ERROR:PUSHRACED', [('message', str(exc))])
            return streamres(bundler.getchunks())
        else:
            return pusherr(str(exc))