lfs: show a friendly message when pushing lfs to a server without lfs enabled

Upfront disclaimer: I don't know anything about the wire protocol, and this was
pretty much cargo-culted from largefiles, and then clonebundles, since it seems
more modern.  I was surprised that exchange.push() will ensure all of the proper
requirements when exchanging between two local repos, but doesn't care when one
is remote.

All this new capability marker does is inform the client that the extension is
enabled remotely.  It may or may not contain commits with external blobs.

Open issues:

  - largefiles uses 'largefiles=serve' for its capability.  Someday I hope to
    be able to push lfs blobs to an `hg serve` instance.  That will probably
    require a distinct capability.  Should it change to '=serve' then?  Or just
    add an 'lfs-serve' capability then?

  - The flip side of this is more complicated.  It looks like largefiles adds an
    'lheads' command for the client to signal to the server that the extension
    is loaded.  That is then converted to 'heads' and sent through the normal
    wire protocol plumbing.  A client using the 'heads' command directly is
    kicked out with a message indicating that the largefiles extension must be
    loaded.  We could do similar with 'lfsheads', but then a repo with both
    largefiles and lfs blobs can't be pushed over the wire.  Hopefully somebody
    with more wire protocol experience can think of something else.  I see
    'x-hgarg-1' on some commands in the tests, but not on heads, and didn't dig
    any further.

hgext/lfs/__init__.py

@@ -1,214 +1,218 b''
 # lfs - hash-preserving large file support using Git-LFS protocol
 #
 # Copyright 2017 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 """lfs - large file support (EXPERIMENTAL)
 
 Configs::
 
     [lfs]
     # Remote endpoint. Multiple protocols are supported:
     # - http(s)://user:[e-mail]/path
     #   git-lfs endpoint
     # - file:///tmp/path
     #   local filesystem, usually for testing
     # if unset, lfs will prompt setting this when it must use this value.
     # (default: unset)
     url = https://example.com/lfs
 
     # size of a file to make it use LFS
     threshold = 10M
 
     # how many times to retry before giving up on transferring an object
     retry = 5
 
     # the local directory to store lfs files for sharing across local clones.
     # If not set, the cache is located in an OS specific cache location.
     usercache = /path/to/global/cache
 """
 
 from __future__ import absolute_import
 
 from mercurial.i18n import _
 
 from mercurial import (
     bundle2,
     changegroup,
     context,
     exchange,
     extensions,
     filelog,
     hg,
     localrepo,
     node,
     registrar,
     revlog,
     scmutil,
     upgrade,
     vfs as vfsmod,
+    wireproto,
 )
 
 from . import (
     blobstore,
     wrapper,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 configtable = {}
 configitem = registrar.configitem(configtable)
 
 configitem('experimental', 'lfs.user-agent',
     default=None,
 )
 
 configitem('lfs', 'url',
     default=configitem.dynamicdefault,
 )
 configitem('lfs', 'usercache',
     default=None,
 )
 configitem('lfs', 'threshold',
     default=None,
 )
 configitem('lfs', 'retry',
     default=5,
 )
 # Deprecated
 configitem('lfs', 'remotestore',
     default=None,
 )
 # Deprecated
 configitem('lfs', 'dummy',
     default=None,
 )
 # Deprecated
 configitem('lfs', 'git-lfs',
     default=None,
 )
 
 cmdtable = {}
 command = registrar.command(cmdtable)
 
 templatekeyword = registrar.templatekeyword()
 
 def featuresetup(ui, supported):
     # don't die on seeing a repo with the lfs requirement
     supported |= {'lfs'}
 
 def uisetup(ui):
     localrepo.localrepository.featuresetupfuncs.add(featuresetup)
 
 def reposetup(ui, repo):
     # Nothing to do with a remote repo
     if not repo.local():
         return
 
     threshold = repo.ui.configbytes('lfs', 'threshold')
 
     repo.svfs.options['lfsthreshold'] = threshold
     repo.svfs.lfslocalblobstore = blobstore.local(repo)
     repo.svfs.lfsremoteblobstore = blobstore.remote(repo)
 
     # Push hook
     repo.prepushoutgoinghooks.add('lfs', wrapper.prepush)
 
     if 'lfs' not in repo.requirements:
         def checkrequireslfs(ui, repo, **kwargs):
             if 'lfs' not in repo.requirements:
                 last = kwargs.get('node_last')
                 _bin = node.bin
                 if last:
                     s = repo.set('%n:%n', _bin(kwargs['node']), _bin(last))
                 else:
                     s = repo.set('%n', _bin(kwargs['node']))
             for ctx in s:
                 # TODO: is there a way to just walk the files in the commit?
                 if any(ctx[f].islfs() for f in ctx.files() if f in ctx):
                     repo.requirements.add('lfs')
                     repo._writerequirements()
                     break
 
         ui.setconfig('hooks', 'commit.lfs', checkrequireslfs, 'lfs')
         ui.setconfig('hooks', 'pretxnchangegroup.lfs', checkrequireslfs, 'lfs')
 
 def wrapfilelog(filelog):
     wrapfunction = extensions.wrapfunction
 
     wrapfunction(filelog, 'addrevision', wrapper.filelogaddrevision)
     wrapfunction(filelog, 'renamed', wrapper.filelogrenamed)
     wrapfunction(filelog, 'size', wrapper.filelogsize)
 
 def extsetup(ui):
     wrapfilelog(filelog.filelog)
 
     wrapfunction = extensions.wrapfunction
 
     wrapfunction(scmutil, 'wrapconvertsink', wrapper.convertsink)
 
     wrapfunction(upgrade, '_finishdatamigration',
                  wrapper.upgradefinishdatamigration)
 
     wrapfunction(upgrade, 'preservedrequirements',
                  wrapper.upgraderequirements)
 
     wrapfunction(upgrade, 'supporteddestrequirements',
                  wrapper.upgraderequirements)
 
     wrapfunction(changegroup,
                  'supportedoutgoingversions',
                  wrapper.supportedoutgoingversions)
     wrapfunction(changegroup,
                  'allsupportedversions',
                  wrapper.allsupportedversions)
 
+    wrapfunction(exchange, 'push', wrapper.push)
+    wrapfunction(wireproto, '_capabilities', wrapper._capabilities)
+
     wrapfunction(context.basefilectx, 'cmp', wrapper.filectxcmp)
     wrapfunction(context.basefilectx, 'isbinary', wrapper.filectxisbinary)
     context.basefilectx.islfs = wrapper.filectxislfs
 
     revlog.addflagprocessor(
         revlog.REVIDX_EXTSTORED,
         (
             wrapper.readfromstore,
             wrapper.writetostore,
             wrapper.bypasscheckhash,
         ),
     )
 
     wrapfunction(hg, 'clone', wrapper.hgclone)
     wrapfunction(hg, 'postshare', wrapper.hgpostshare)
 
     # Make bundle choose changegroup3 instead of changegroup2. This affects
     # "hg bundle" command. Note: it does not cover all bundle formats like
     # "packed1". Using "packed1" with lfs will likely cause trouble.
     names = [k for k, v in exchange._bundlespeccgversions.items() if v == '02']
     for k in names:
         exchange._bundlespeccgversions[k] = '03'
 
     # bundlerepo uses "vfsmod.readonlyvfs(othervfs)", we need to make sure lfs
     # options and blob stores are passed from othervfs to the new readonlyvfs.
     wrapfunction(vfsmod.readonlyvfs, '__init__', wrapper.vfsinit)
 
     # when writing a bundle via "hg bundle" command, upload related LFS blobs
     wrapfunction(bundle2, 'writenewbundle', wrapper.writenewbundle)
 
 @templatekeyword('lfs_files')
 def lfsfiles(repo, ctx, **args):
     """List of strings. LFS files added or modified by the changeset."""
     pointers = wrapper.pointersfromctx(ctx) # {path: pointer}
     return sorted(pointers.keys())
 
 @command('debuglfsupload',
          [('r', 'rev', [], _('upload large files introduced by REV'))])
 def debuglfsupload(ui, repo, **opts):
     """upload lfs blobs added by the working copy parent or given revisions"""
     revs = opts.get('rev', [])
     pointers = wrapper.extractpointers(repo, scmutil.revrange(repo, revs))
     wrapper.uploadblobs(repo, pointers)

hgext/lfs/wrapper.py

@@ -1,324 +1,345 b''
 # wrapper.py - methods wrapping core mercurial logic
 #
 # Copyright 2017 Facebook, Inc.
 #
 # 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
 
 import hashlib
 
 from mercurial.i18n import _
 from mercurial.node import bin, nullid, short
 
 from mercurial import (
     error,
     filelog,
     revlog,
     util,
 )
 
 from ..largefiles import lfutil
 
 from . import (
     blobstore,
     pointer,
 )
 
 def supportedoutgoingversions(orig, repo):
     versions = orig(repo)
     if 'lfs' in repo.requirements:
         versions.discard('01')
         versions.discard('02')
     versions.add('03')
     return versions
 
 def allsupportedversions(orig, ui):
     versions = orig(ui)
     versions.add('03')
     return versions
 
+def _capabilities(orig, repo, proto):
+    '''Wrap server command to announce lfs server capability'''
+    caps = orig(repo, proto)
+    # XXX: change to 'lfs=serve' when separate git server isn't required?
+    caps.append('lfs')
+    return caps
+
 def bypasscheckhash(self, text):
     return False
 
 def readfromstore(self, text):
     """Read filelog content from local blobstore transform for flagprocessor.
 
     Default tranform for flagprocessor, returning contents from blobstore.
     Returns a 2-typle (text, validatehash) where validatehash is True as the
     contents of the blobstore should be checked using checkhash.
     """
     p = pointer.deserialize(text)
     oid = p.oid()
     store = self.opener.lfslocalblobstore
     if not store.has(oid):
         p.filename = getattr(self, 'indexfile', None)
         self.opener.lfsremoteblobstore.readbatch([p], store)
 
     # The caller will validate the content
     text = store.read(oid, verify=False)
 
     # pack hg filelog metadata
     hgmeta = {}
     for k in p.keys():
         if k.startswith('x-hg-'):
             name = k[len('x-hg-'):]
             hgmeta[name] = p[k]
     if hgmeta or text.startswith('\1\n'):
         text = filelog.packmeta(hgmeta, text)
 
     return (text, True)
 
 def writetostore(self, text):
     # hg filelog metadata (includes rename, etc)
     hgmeta, offset = filelog.parsemeta(text)
     if offset and offset > 0:
         # lfs blob does not contain hg filelog metadata
         text = text[offset:]
 
     # git-lfs only supports sha256
     oid = hashlib.sha256(text).hexdigest()
     self.opener.lfslocalblobstore.write(oid, text, verify=False)
 
     # replace contents with metadata
     longoid = 'sha256:%s' % oid
     metadata = pointer.gitlfspointer(oid=longoid, size=str(len(text)))
 
     # by default, we expect the content to be binary. however, LFS could also
     # be used for non-binary content. add a special entry for non-binary data.
     # this will be used by filectx.isbinary().
     if not util.binary(text):
         # not hg filelog metadata (affecting commit hash), no "x-hg-" prefix
         metadata['x-is-binary'] = '0'
 
     # translate hg filelog metadata to lfs metadata with "x-hg-" prefix
     if hgmeta is not None:
         for k, v in hgmeta.iteritems():
             metadata['x-hg-%s' % k] = v
 
     rawtext = metadata.serialize()
     return (rawtext, False)
 
 def _islfs(rlog, node=None, rev=None):
     if rev is None:
         if node is None:
             # both None - likely working copy content where node is not ready
             return False
         rev = rlog.rev(node)
     else:
         node = rlog.node(rev)
     if node == nullid:
         return False
     flags = rlog.flags(rev)
     return bool(flags & revlog.REVIDX_EXTSTORED)
 
 def filelogaddrevision(orig, self, text, transaction, link, p1, p2,
                        cachedelta=None, node=None,
                        flags=revlog.REVIDX_DEFAULT_FLAGS, **kwds):
     threshold = self.opener.options['lfsthreshold']
     textlen = len(text)
     # exclude hg rename meta from file size
     meta, offset = filelog.parsemeta(text)
     if offset:
         textlen -= offset
 
     if threshold and textlen > threshold:
         flags |= revlog.REVIDX_EXTSTORED
 
     return orig(self, text, transaction, link, p1, p2, cachedelta=cachedelta,
                 node=node, flags=flags, **kwds)
 
 def filelogrenamed(orig, self, node):
     if _islfs(self, node):
         rawtext = self.revision(node, raw=True)
         if not rawtext:
             return False
         metadata = pointer.deserialize(rawtext)
         if 'x-hg-copy' in metadata and 'x-hg-copyrev' in metadata:
             return metadata['x-hg-copy'], bin(metadata['x-hg-copyrev'])
         else:
             return False
     return orig(self, node)
 
 def filelogsize(orig, self, rev):
     if _islfs(self, rev=rev):
         # fast path: use lfs metadata to answer size
         rawtext = self.revision(rev, raw=True)
         metadata = pointer.deserialize(rawtext)
         return int(metadata['size'])
     return orig(self, rev)
 
 def filectxcmp(orig, self, fctx):
     """returns True if text is different than fctx"""
     # some fctx (ex. hg-git) is not based on basefilectx and do not have islfs
     if self.islfs() and getattr(fctx, 'islfs', lambda: False)():
         # fast path: check LFS oid
         p1 = pointer.deserialize(self.rawdata())
         p2 = pointer.deserialize(fctx.rawdata())
         return p1.oid() != p2.oid()
     return orig(self, fctx)
 
 def filectxisbinary(orig, self):
     if self.islfs():
         # fast path: use lfs metadata to answer isbinary
         metadata = pointer.deserialize(self.rawdata())
         # if lfs metadata says nothing, assume it's binary by default
         return bool(int(metadata.get('x-is-binary', 1)))
     return orig(self)
 
 def filectxislfs(self):
     return _islfs(self.filelog(), self.filenode())
 
 def convertsink(orig, sink):
     sink = orig(sink)
     if sink.repotype == 'hg':
         class lfssink(sink.__class__):
             def putcommit(self, files, copies, parents, commit, source, revmap,
                           full, cleanp2):
                 pc = super(lfssink, self).putcommit
                 node = pc(files, copies, parents, commit, source, revmap, full,
                           cleanp2)
 
                 if 'lfs' not in self.repo.requirements:
                     ctx = self.repo[node]
 
                     # The file list may contain removed files, so check for
                     # membership before assuming it is in the context.
                     if any(f in ctx and ctx[f].islfs() for f, n in files):
                         self.repo.requirements.add('lfs')
                         self.repo._writerequirements()
 
                         # Permanently enable lfs locally
                         with self.repo.vfs('hgrc', 'a', text=True) as fp:
                             fp.write('\n[extensions]\nlfs=\n')
 
                 return node
 
         sink.__class__ = lfssink
 
     return sink
 
 def vfsinit(orig, self, othervfs):
     orig(self, othervfs)
     # copy lfs related options
     for k, v in othervfs.options.items():
         if k.startswith('lfs'):
             self.options[k] = v
     # also copy lfs blobstores. note: this can run before reposetup, so lfs
     # blobstore attributes are not always ready at this time.
     for name in ['lfslocalblobstore', 'lfsremoteblobstore']:
         if util.safehasattr(othervfs, name):
             setattr(self, name, getattr(othervfs, name))
 
 def hgclone(orig, ui, opts, *args, **kwargs):
     result = orig(ui, opts, *args, **kwargs)
 
     if result is not None:
         sourcerepo, destrepo = result
         repo = destrepo.local()
 
         # When cloning to a remote repo (like through SSH), no repo is available
         # from the peer.  Therefore the hgrc can't be updated.
         if not repo:
             return result
 
         # If lfs is required for this repo, permanently enable it locally
         if 'lfs' in repo.requirements:
             with repo.vfs('hgrc', 'a', text=True) as fp:
                 fp.write('\n[extensions]\nlfs=\n')
 
     return result
 
 def hgpostshare(orig, sourcerepo, destrepo, bookmarks=True, defaultpath=None):
     orig(sourcerepo, destrepo, bookmarks, defaultpath)
 
     # If lfs is required for this repo, permanently enable it locally
     if 'lfs' in destrepo.requirements:
         with destrepo.vfs('hgrc', 'a', text=True) as fp:
             fp.write('\n[extensions]\nlfs=\n')
 
 def _canskipupload(repo):
     # if remotestore is a null store, upload is a no-op and can be skipped
     return isinstance(repo.svfs.lfsremoteblobstore, blobstore._nullremote)
 
 def candownload(repo):
     # if remotestore is a null store, downloads will lead to nothing
     return not isinstance(repo.svfs.lfsremoteblobstore, blobstore._nullremote)
 
 def uploadblobsfromrevs(repo, revs):
     '''upload lfs blobs introduced by revs
 
     Note: also used by other extensions e. g. infinitepush. avoid renaming.
     '''
     if _canskipupload(repo):
         return
     pointers = extractpointers(repo, revs)
     uploadblobs(repo, pointers)
 
 def prepush(pushop):
     """Prepush hook.
 
     Read through the revisions to push, looking for filelog entries that can be
     deserialized into metadata so that we can block the push on their upload to
     the remote blobstore.
     """
     return uploadblobsfromrevs(pushop.repo, pushop.outgoing.missing)
 
+def push(orig, repo, remote, *args, **kwargs):
+    """bail on push if the extension isn't enabled on remote when needed"""
+    if 'lfs' in repo.requirements:
+        # If the remote peer is for a local repo, the requirement tests in the
+        # base class method enforce lfs support.  Otherwise, some revisions in
+        # this repo use lfs, and the remote repo needs the extension loaded.
+        if not remote.local() and not remote.capable('lfs'):
+            # This is a copy of the message in exchange.push() when requirements
+            # are missing between local repos.
+            m = _("required features are not supported in the destination: %s")
+            raise error.Abort(m % 'lfs',
+                              hint=_('enable the lfs extension on the server'))
+    return orig(repo, remote, *args, **kwargs)
+
 def writenewbundle(orig, ui, repo, source, filename, bundletype, outgoing,
                    *args, **kwargs):
     """upload LFS blobs added by outgoing revisions on 'hg bundle'"""
     uploadblobsfromrevs(repo, outgoing.missing)
     return orig(ui, repo, source, filename, bundletype, outgoing, *args,
                 **kwargs)
 
 def extractpointers(repo, revs):
     """return a list of lfs pointers added by given revs"""
     repo.ui.debug('lfs: computing set of blobs to upload\n')
     pointers = {}
     for r in revs:
         ctx = repo[r]
         for p in pointersfromctx(ctx).values():
             pointers[p.oid()] = p
     return sorted(pointers.values())
 
 def pointersfromctx(ctx):
     """return a dict {path: pointer} for given single changectx"""
     result = {}
     for f in ctx.files():
         if f not in ctx:
             continue
         fctx = ctx[f]
         if not _islfs(fctx.filelog(), fctx.filenode()):
             continue
         try:
             result[f] = pointer.deserialize(fctx.rawdata())
         except pointer.InvalidPointer as ex:
             raise error.Abort(_('lfs: corrupted pointer (%s@%s): %s\n')
                               % (f, short(ctx.node()), ex))
     return result
 
 def uploadblobs(repo, pointers):
     """upload given pointers from local blobstore"""
     if not pointers:
         return
 
     remoteblob = repo.svfs.lfsremoteblobstore
     remoteblob.writebatch(pointers, repo.svfs.lfslocalblobstore)
 
 def upgradefinishdatamigration(orig, ui, srcrepo, dstrepo, requirements):
     orig(ui, srcrepo, dstrepo, requirements)
 
     srclfsvfs = srcrepo.svfs.lfslocalblobstore.vfs
     dstlfsvfs = dstrepo.svfs.lfslocalblobstore.vfs
 
     for dirpath, dirs, files in srclfsvfs.walk():
         for oid in files:
             ui.write(_('copying lfs blob %s\n') % oid)
             lfutil.link(srclfsvfs.join(oid), dstlfsvfs.join(oid))
 
 def upgraderequirements(orig, repo):
     reqs = orig(repo)
     if 'lfs' in repo.requirements:
         reqs.add('lfs')
     return reqs

tests/test-lfs-serve.t

@@ -1,279 +1,283 b''
 #testcases lfsremote-on lfsremote-off
 #require serve
 
 This test splits `hg serve` with and without using the extension into separate
 tests cases.  The tests are broken down as follows, where "LFS"/"No-LFS"
 indicates whether or not there are commits that use an LFS file, and "D"/"E"
 indicates whether or not the extension is loaded.  The "X" cases are not tested
 individually, because the lfs requirement causes the process to bail early if
 the extension is disabled.
 
 .                        Server
 .
 .                    No-LFS        LFS
 .            +----------------------------+
 .            |   ||  D  |  E  |  D  |  E  |
 .            |---++=======================|
 .  C         | D || N/A | #1  |  X  | #4  |
 .  l    No   +---++-----------------------|
 .  i    LFS  | E || #2  | #2  |  X  | #5  |
 .  e         +---++-----------------------|
 .  n         | D ||  X  |  X  |  X  |  X  |
 .  t    LFS  |---++-----------------------|
 .            | E || #3  | #3  |  X  | #6  |
 .            |---++-----------------------+
 
   $ hg init server
   $ SERVER_REQUIRES="$TESTTMP/server/.hg/requires"
 
 Skip the experimental.changegroup3=True config.  Failure to agree on this comes
 first, and causes a "ValueError: no common changegroup version" or "abort:
 HTTP Error 500: Internal Server Error", if the extension is only loaded on one
 side.  If that *is* enabled, the subsequent failure is "abort: missing processor
 for flag '0x2000'!" if the extension is only loaded on one side (possibly also
 masked by the Internal Server Error message).
   $ cat >> $HGRCPATH <<EOF
   > [lfs]
   > url=file:$TESTTMP/dummy-remote/
   > threshold=10
   > [web]
   > allow_push=*
   > push_ssl=False
   > EOF
 
 #if lfsremote-on
   $ hg --config extensions.lfs= -R server \
   >    serve -p $HGPORT -d --pid-file=hg.pid --errorlog=$TESTTMP/errors.log
 #else
   $ hg --config extensions.lfs=! -R server \
   >    serve -p $HGPORT -d --pid-file=hg.pid --errorlog=$TESTTMP/errors.log
 #endif
 
   $ cat hg.pid >> $DAEMON_PIDS
   $ hg clone -q http://localhost:$HGPORT client
   $ grep 'lfs' client/.hg/requires $SERVER_REQUIRES
   [1]
 
 --------------------------------------------------------------------------------
 Case #1: client with non-lfs content and the extension disabled; server with
 non-lfs content, and the extension enabled.
 
   $ cd client
   $ echo 'non-lfs' > nonlfs.txt
   $ hg ci -Aqm 'non-lfs'
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   [1]
 
 #if lfsremote-on
 
   $ hg push -q
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client1_clone
   $ grep 'lfs' $TESTTMP/client1_clone/.hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg init $TESTTMP/client1_pull
   $ hg -R $TESTTMP/client1_pull pull -q http://localhost:$HGPORT
   $ grep 'lfs' $TESTTMP/client1_pull/.hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg identify http://localhost:$HGPORT
   d437e1d24fbd
 
 #endif
 
 --------------------------------------------------------------------------------
 Case #2: client with non-lfs content and the extension enabled; server with
 non-lfs content, and the extension state controlled by #testcases.
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > lfs =
   > EOF
   $ echo 'non-lfs' > nonlfs2.txt
   $ hg ci -Aqm 'non-lfs file with lfs client'
 
 Since no lfs content has been added yet, the push is allowed, even when the
 extension is not enabled remotely.
 
   $ hg push -q
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client2_clone
   $ grep 'lfs' $TESTTMP/client2_clone/.hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg init $TESTTMP/client2_pull
   $ hg -R $TESTTMP/client2_pull pull -q http://localhost:$HGPORT
   $ grep 'lfs' $TESTTMP/client2_pull/.hg/requires $SERVER_REQUIRES
   [1]
 
   $ hg identify http://localhost:$HGPORT
   1477875038c6
 
 --------------------------------------------------------------------------------
 Case #3: client with lfs content and the extension enabled; server with
 non-lfs content, and the extension state controlled by #testcases.  The server
 should have an 'lfs' requirement after it picks up its first commit with a blob.
 
   $ echo 'this is a big lfs file' > lfs.bin
   $ hg ci -Aqm 'lfs'
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   .hg/requires:lfs
 
-TODO: fail more gracefully here
-  $ hg push -q 2>&1 | grep '^[A-Z]' || true
-  Traceback (most recent call last): (lfsremote-off !)
-  ValueError: no common changegroup version (lfsremote-off !)
+#if lfsremote-off
+  $ hg push -q
+  abort: required features are not supported in the destination: lfs
+  (enable the lfs extension on the server)
+  [255]
+#else
+  $ hg push -q
+#endif
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   .hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs (lfsremote-on !)
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client3_clone
   $ grep 'lfs' $TESTTMP/client3_clone/.hg/requires $SERVER_REQUIRES || true
   $TESTTMP/client3_clone/.hg/requires:lfs (lfsremote-on !)
   $TESTTMP/server/.hg/requires:lfs (lfsremote-on !)
 
   $ hg init $TESTTMP/client3_pull
   $ hg -R $TESTTMP/client3_pull pull -q http://localhost:$HGPORT
   $ grep 'lfs' $TESTTMP/client3_pull/.hg/requires $SERVER_REQUIRES || true
   $TESTTMP/client3_pull/.hg/requires:lfs (lfsremote-on !)
   $TESTTMP/server/.hg/requires:lfs (lfsremote-on !)
 
 The difference here is the push failed above when the extension isn't
 enabled on the server.
   $ hg identify http://localhost:$HGPORT
   8374dc4052cb (lfsremote-on !)
   1477875038c6 (lfsremote-off !)
 
 Don't bother testing the lfsremote-off cases- the server won't be able
 to launch if there's lfs content and the extension is disabled.
 
 #if lfsremote-on
 
 --------------------------------------------------------------------------------
 Case #4: client with non-lfs content and the extension disabled; server with
 lfs content, and the extension enabled.
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > lfs = !
   > EOF
 
   $ hg init $TESTTMP/client4
   $ cd $TESTTMP/client4
   $ cat >> .hg/hgrc <<EOF
   > [paths]
   > default = http://localhost:$HGPORT
   > EOF
   $ echo 'non-lfs' > nonlfs2.txt
   $ hg ci -Aqm 'non-lfs'
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg push -q --force
   warning: repository is unrelated
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   $TESTTMP/server/.hg/requires:lfs
 
 TODO: fail more gracefully.
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client4_clone
   abort: HTTP Error 500: Internal Server Error
   [255]
   $ grep 'lfs' $TESTTMP/client4_clone/.hg/requires $SERVER_REQUIRES
   grep: $TESTTMP/client4_clone/.hg/requires: $ENOENT$
   $TESTTMP/server/.hg/requires:lfs
   [2]
 
 TODO: fail more gracefully.
 
   $ hg init $TESTTMP/client4_pull
   $ hg -R $TESTTMP/client4_pull pull -q http://localhost:$HGPORT
   abort: HTTP Error 500: Internal Server Error
   [255]
   $ grep 'lfs' $TESTTMP/client4_pull/.hg/requires $SERVER_REQUIRES
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg identify http://localhost:$HGPORT
   03b080fa9d93
 
 --------------------------------------------------------------------------------
 Case #5: client with non-lfs content and the extension enabled; server with
 lfs content, and the extension enabled.
 
   $ cat >> $HGRCPATH <<EOF
   > [extensions]
   > lfs =
   > EOF
   $ echo 'non-lfs' > nonlfs3.txt
   $ hg ci -Aqm 'non-lfs file with lfs client'
 
   $ hg push -q
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client5_clone
   $ grep 'lfs' $TESTTMP/client5_clone/.hg/requires $SERVER_REQUIRES
   $TESTTMP/client5_clone/.hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg init $TESTTMP/client5_pull
   $ hg -R $TESTTMP/client5_pull pull -q http://localhost:$HGPORT
   $ grep 'lfs' $TESTTMP/client5_pull/.hg/requires $SERVER_REQUIRES
   $TESTTMP/client5_pull/.hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg identify http://localhost:$HGPORT
   c729025cc5e3
 
 --------------------------------------------------------------------------------
 Case #6: client with lfs content and the extension enabled; server with
 lfs content, and the extension enabled.
 
   $ echo 'this is another lfs file' > lfs2.txt
   $ hg ci -Aqm 'lfs file with lfs client'
 
   $ hg push -q
   $ grep 'lfs' .hg/requires $SERVER_REQUIRES
   .hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg clone -q http://localhost:$HGPORT $TESTTMP/client6_clone
   $ grep 'lfs' $TESTTMP/client6_clone/.hg/requires $SERVER_REQUIRES
   $TESTTMP/client6_clone/.hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg init $TESTTMP/client6_pull
   $ hg -R $TESTTMP/client6_pull pull -q http://localhost:$HGPORT
   $ grep 'lfs' $TESTTMP/client6_pull/.hg/requires $SERVER_REQUIRES
   $TESTTMP/client6_pull/.hg/requires:lfs
   $TESTTMP/server/.hg/requires:lfs
 
   $ hg identify http://localhost:$HGPORT
   d3b84d50eacb
 
 --------------------------------------------------------------------------------
 Misc: process dies early if a requirement exists and the extension is disabled
 
   $ hg --config extensions.lfs=! summary
   abort: repository requires features unknown to this Mercurial: lfs!
   (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
   [255]
 
 #endif
 
   $ $PYTHON $TESTDIR/killdaemons.py $DAEMON_PIDS
 
 #if lfsremote-on
   $ cat $TESTTMP/errors.log | grep '^[A-Z]'
   Traceback (most recent call last):
   ValueError: no common changegroup version
   Traceback (most recent call last):
   ValueError: no common changegroup version
 #else
   $ cat $TESTTMP/errors.log
 #endif