view tests/test-ssh-bundle1.t @ 30155:b7a966ce89ed

changelog: disable delta chains

This patch disables delta chains on changelogs. After this patch, new
entries on changelogs - including existing changelogs - will be stored
as the fulltext of that data (likely compressed). No delta computation
will be performed.

An overview of delta chains and data justifying this change follows.

Revlogs try to store entries as a delta against a previous entry (either
a parent revision in the case of generaldelta or the previous physical
revision when not using generaldelta). Most of the time this is the
correct thing to do: it frequently results in less CPU usage and smaller
storage.

Delta chains are most effective when the base revision being deltad
against is similar to the current data. This tends to occur naturally
for manifests and file data, since only small parts of each tend to
change with each revision. Changelogs, however, are a different story.

Changelog entries represent changesets/commits. And unless commits in a
repository are homogonous (same author, changing same files, similar
commit messages, etc), a delta from one entry to the next tends to be
relatively large compared to the size of the entry. This means that
delta chains tend to be short. How short? Here is the full vs delta
revision breakdown on some real world repos:

Repo             % Full    % Delta   Max Length
hg                45.8       54.2        6
mozilla-central   42.4       57.6        8
mozilla-unified   42.5       57.5       17
pypy              46.1       53.9        6
python-zstandard  46.1       53.9        3

(I threw in python-zstandard as an example of a repo that is homogonous.
It contains a small Python project with changes all from the same
author.)

Contrast this with the manifest revlog for these repos, where 99+% of
revisions are deltas and delta chains run into the thousands.

So delta chains aren't as useful on changelogs. But even a short delta
chain may provide benefits. Let's measure that.

Delta chains may require less CPU to read revisions if the CPU time
spent reading smaller deltas is less than the CPU time used to
decompress larger individual entries. We can measure this via
`hg perfrevlog -c -d 1` to iterate a revlog to resolve each revision's
fulltext. Here are the results of that command on a repo using delta
chains in its changelog and on a repo without delta chains:

hg (forward)
! wall 0.407008 comb 0.410000 user 0.410000 sys 0.000000 (best of 25)
! wall 0.390061 comb 0.390000 user 0.390000 sys 0.000000 (best of 26)

hg (reverse)
! wall 0.515221 comb 0.520000 user 0.520000 sys 0.000000 (best of 19)
! wall 0.400018 comb 0.400000 user 0.390000 sys 0.010000 (best of 25)

mozilla-central (forward)
! wall 4.508296 comb 4.490000 user 4.490000 sys 0.000000 (best of 3)
! wall 4.370222 comb 4.370000 user 4.350000 sys 0.020000 (best of 3)

mozilla-central (reverse)
! wall 5.758995 comb 5.760000 user 5.720000 sys 0.040000 (best of 3)
! wall 4.346503 comb 4.340000 user 4.320000 sys 0.020000 (best of 3)

mozilla-unified (forward)
! wall 4.957088 comb 4.950000 user 4.940000 sys 0.010000 (best of 3)
! wall 4.660528 comb 4.650000 user 4.630000 sys 0.020000 (best of 3)

mozilla-unified (reverse)
! wall 6.119827 comb 6.110000 user 6.090000 sys 0.020000 (best of 3)
! wall 4.675136 comb 4.670000 user 4.670000 sys 0.000000 (best of 3)

pypy (forward)
! wall 1.231122 comb 1.240000 user 1.230000 sys 0.010000 (best of 8)
! wall 1.164896 comb 1.160000 user 1.160000 sys 0.000000 (best of 9)

pypy (reverse)
! wall 1.467049 comb 1.460000 user 1.460000 sys 0.000000 (best of 7)
! wall 1.160200 comb 1.170000 user 1.160000 sys 0.010000 (best of 9)

The data clearly shows that it takes less wall and CPU time to resolve
revisions when there are no delta chains in the changelogs, regardless
of the direction of traversal. Furthermore, not using a delta chain
means that fulltext resolution in reverse is as fast as iterating
forward. So not using delta chains on the changelog is a clear CPU win
for reading operations.

An example of a user-visible operation showing this speed-up is revset
evaluation. Here are results for
`hg perfrevset 'author(gps) or author(mpm)'`:

hg
! wall 1.655506 comb 1.660000 user 1.650000 sys 0.010000 (best of 6)
! wall 1.612723 comb 1.610000 user 1.600000 sys 0.010000 (best of 7)

mozilla-central
! wall 17.629826 comb 17.640000 user 17.600000 sys 0.040000 (best of 3)
! wall 17.311033 comb 17.300000 user 17.260000 sys 0.040000 (best of 3)

What about 00changelog.i size?

Repo                Delta Chains     No Delta Chains
hg                    7,033,250         6,976,771
mozilla-central      82,978,748        81,574,623
mozilla-unified      88,112,349        86,702,162
pypy                 20,740,699        20,659,741

The data shows that removing delta chains from the changelog makes the
changelog smaller.

Delta chains are also used during changegroup generation. This
operation essentially converts a series of revisions to one large
delta chain. And changegroup generation is smart: if the delta in
the revlog matches what the changegroup is emitting, it will reuse
the delta instead of recalculating it. We can measure the impact
removing changelog delta chains has on changegroup generation via
`hg perfchangegroupchangelog`:

hg
! wall 1.589245 comb 1.590000 user 1.590000 sys 0.000000 (best of 7)
! wall 1.788060 comb 1.790000 user 1.790000 sys 0.000000 (best of 6)

mozilla-central
! wall 17.382585 comb 17.380000 user 17.340000 sys 0.040000 (best of 3)
! wall 20.161357 comb 20.160000 user 20.120000 sys 0.040000 (best of 3)

mozilla-unified
! wall 18.722839 comb 18.720000 user 18.680000 sys 0.040000 (best of 3)
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)

pypy
! wall 4.828317 comb 4.830000 user 4.820000 sys 0.010000 (best of 3)
! wall 5.415455 comb 5.420000 user 5.410000 sys 0.010000 (best of 3)

The data shows eliminating delta chains makes the changelog part of
changegroup generation slower. This is expected since we now have to
compute deltas for revisions where we could recycle the delta before.

It is worth putting this regression into context of overall changegroup
times. Here is the rough total CPU time spent in changegroup generation
for various repos while using delta chains on the changelog:

Repo              CPU Time (s)    CPU Time w/ compression
hg                  4.50              7.05
mozilla-central   111.1             222.0
pypy               28.68             75.5

Before compression, removing delta chains from the changegroup adds
~4.4% overhead to hg changegroup generation, 1.3% to mozilla-central,
and 2.0% to pypy. When you factor in zlib compression, these percentages
are roughly divided by 2.

While the increased CPU usage for changegroup generation is unfortunate,
I think it is acceptable because the percentage is small, server
operators (those likely impacted most by this) have other mechanisms
to mitigate CPU consumption (namely reducing zlib compression level and
pre-generated clone bundles), and because there is room to optimize this
in the future. For example, we could use the nullid as the base revision,
effectively encoding the full revision for each entry in the changegroup.
When doing this, `hg perfchangegroupchangelog` nearly halves:

mozilla-unified
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)
! wall 11.196461 comb 11.200000 user 11.190000 sys 0.010000 (best of 3)

This looks very promising as a future optimization opportunity.

It's worth that the changes in test-acl.t to the changegroup part size.
This is because revision 6 in the changegroup had a delta chain of
length 2 before and after this patch the base revision is nullrev.
When the base revision is nullrev, cg2packer.deltaparent() hardcodes
the *previous* revision from the changegroup as the delta parent.
This caused the delta in the changegroup to switch base revisions,
the delta to change, and the size to change accordingly. While the
size increased in this case, I think sizes will remain the same
on average, as the delta base for changelog revisions doesn't matter
too much (as this patch shows). So, I don't consider this a regression.

This test is a duplicate of 'test-http.t' feel free to factor out
parts that are not bundle1/bundle2 specific.

  $ cat << EOF >> $HGRCPATH
  > [devel]
  > # This test is dedicated to interaction through old bundle
  > legacy.exchange = bundle1
  > [format] # temporary settings
  > usegeneraldelta=yes
  > EOF


This test tries to exercise the ssh functionality with a dummy script

creating 'remote' repo

  $ hg init remote
  $ cd remote
  $ echo this > foo
  $ echo this > fooO
  $ hg ci -A -m "init" foo fooO

insert a closed branch (issue4428)

  $ hg up null
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg branch closed
  marked working directory as branch closed
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -mc0
  $ hg ci --close-branch -mc1
  $ hg up -q default

configure for serving

  $ cat <<EOF > .hg/hgrc
  > [server]
  > uncompressed = True
  > 
  > [hooks]
  > changegroup = printenv.py changegroup-in-remote 0 ../dummylog
  > EOF
  $ cd ..

repo not found error

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/nonexistent local
  remote: abort: repository nonexistent not found!
  abort: no suitable response from remote hg!
  [255]

non-existent absolute path

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy//`pwd`/nonexistent local
  remote: abort: repository /$TESTTMP/nonexistent not found!
  abort: no suitable response from remote hg!
  [255]

clone remote via stream

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/remote local-stream
  streaming all changes
  4 files to transfer, 602 bytes of data
  transferred 602 bytes in * seconds (*) (glob)
  searching for changes
  no changes found
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd local-stream
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 3 changesets, 2 total revisions
  $ hg branches
  default                        0:1160648e36ce
  $ cd ..

clone bookmarks via stream

  $ hg -R local-stream book mybook
  $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/local-stream stream2
  streaming all changes
  4 files to transfer, 602 bytes of data
  transferred 602 bytes in * seconds (*) (glob)
  searching for changes
  no changes found
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd stream2
  $ hg book
     mybook                    0:1160648e36ce
  $ cd ..
  $ rm -rf local-stream stream2

clone remote via pull

  $ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote local
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 2 files
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

verify

  $ cd local
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 3 changesets, 2 total revisions
  $ echo '[hooks]' >> .hg/hgrc
  $ echo "changegroup = printenv.py changegroup-in-local 0 ../dummylog" >> .hg/hgrc

empty default pull

  $ hg paths
  default = ssh://user@dummy/remote
  $ hg pull -e "python \"$TESTDIR/dummyssh\""
  pulling from ssh://user@dummy/remote
  searching for changes
  no changes found

pull from wrong ssh URL

  $ hg pull -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/doesnotexist
  pulling from ssh://user@dummy/doesnotexist
  remote: abort: repository doesnotexist not found!
  abort: no suitable response from remote hg!
  [255]

local change

  $ echo bleah > foo
  $ hg ci -m "add"

updating rc

  $ echo "default-push = ssh://user@dummy/remote" >> .hg/hgrc
  $ echo "[ui]" >> .hg/hgrc
  $ echo "ssh = python \"$TESTDIR/dummyssh\"" >> .hg/hgrc

find outgoing

  $ hg out ssh://user@dummy/remote
  comparing with ssh://user@dummy/remote
  searching for changes
  changeset:   3:a28a9d1a809c
  tag:         tip
  parent:      0:1160648e36ce
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add
  

find incoming on the remote side

  $ hg incoming -R ../remote -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/local
  comparing with ssh://user@dummy/local
  searching for changes
  changeset:   3:a28a9d1a809c
  tag:         tip
  parent:      0:1160648e36ce
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add
  

find incoming on the remote side (using absolute path)

  $ hg incoming -R ../remote -e "python \"$TESTDIR/dummyssh\"" "ssh://user@dummy/`pwd`"
  comparing with ssh://user@dummy/$TESTTMP/local
  searching for changes
  changeset:   3:a28a9d1a809c
  tag:         tip
  parent:      0:1160648e36ce
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add
  

push

  $ hg push
  pushing to ssh://user@dummy/remote
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  $ cd ../remote

check remote tip

  $ hg tip
  changeset:   3:a28a9d1a809c
  tag:         tip
  parent:      0:1160648e36ce
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add
  
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 4 changesets, 3 total revisions
  $ hg cat -r tip foo
  bleah
  $ echo z > z
  $ hg ci -A -m z z
  created new head

test pushkeys and bookmarks

  $ cd ../local
  $ hg debugpushkey --config ui.ssh="python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote namespaces
  bookmarks	
  namespaces	
  phases	
  $ hg book foo -r 0
  $ hg out -B
  comparing with ssh://user@dummy/remote
  searching for changed bookmarks
     foo                       1160648e36ce
  $ hg push -B foo
  pushing to ssh://user@dummy/remote
  searching for changes
  no changes found
  exporting bookmark foo
  [1]
  $ hg debugpushkey --config ui.ssh="python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote bookmarks
  foo	1160648e36cec0054048a7edc4110c6f84fde594
  $ hg book -f foo
  $ hg push --traceback
  pushing to ssh://user@dummy/remote
  searching for changes
  no changes found
  updating bookmark foo
  [1]
  $ hg book -d foo
  $ hg in -B
  comparing with ssh://user@dummy/remote
  searching for changed bookmarks
     foo                       a28a9d1a809c
  $ hg book -f -r 0 foo
  $ hg pull -B foo
  pulling from ssh://user@dummy/remote
  no changes found
  updating bookmark foo
  $ hg book -d foo
  $ hg push -B foo
  pushing to ssh://user@dummy/remote
  searching for changes
  no changes found
  deleting remote bookmark foo
  [1]

a bad, evil hook that prints to stdout

  $ cat <<EOF > $TESTTMP/badhook
  > import sys
  > sys.stdout.write("KABOOM\n")
  > EOF

  $ echo '[hooks]' >> ../remote/.hg/hgrc
  $ echo "changegroup.stdout = python $TESTTMP/badhook" >> ../remote/.hg/hgrc
  $ echo r > r
  $ hg ci -A -m z r

push should succeed even though it has an unexpected response

  $ hg push
  pushing to ssh://user@dummy/remote
  searching for changes
  remote has heads on branch 'default' that are not known locally: 6c0482d977a3
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  remote: KABOOM
  $ hg -R ../remote heads
  changeset:   5:1383141674ec
  tag:         tip
  parent:      3:a28a9d1a809c
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     z
  
  changeset:   4:6c0482d977a3
  parent:      0:1160648e36ce
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     z
  

clone bookmarks

  $ hg -R ../remote bookmark test
  $ hg -R ../remote bookmarks
   * test                      4:6c0482d977a3
  $ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/remote local-bookmarks
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 5 changes to 4 files (+1 heads)
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -R local-bookmarks bookmarks
     test                      4:6c0482d977a3

passwords in ssh urls are not supported
(we use a glob here because different Python versions give different
results here)

  $ hg push ssh://user:erroneouspwd@dummy/remote
  pushing to ssh://user:*@dummy/remote (glob)
  abort: password in URL not supported!
  [255]

  $ cd ..

hide outer repo
  $ hg init

Test remote paths with spaces (issue2983):

  $ hg init --ssh "python \"$TESTDIR/dummyssh\"" "ssh://user@dummy/a repo"
  $ touch "$TESTTMP/a repo/test"
  $ hg -R 'a repo' commit -A -m "test"
  adding test
  $ hg -R 'a repo' tag tag
  $ hg id --ssh "python \"$TESTDIR/dummyssh\"" "ssh://user@dummy/a repo"
  73649e48688a

  $ hg id --ssh "python \"$TESTDIR/dummyssh\"" "ssh://user@dummy/a repo#noNoNO"
  abort: unknown revision 'noNoNO'!
  [255]

Test (non-)escaping of remote paths with spaces when cloning (issue3145):

  $ hg clone --ssh "python \"$TESTDIR/dummyssh\"" "ssh://user@dummy/a repo"
  destination directory: a repo
  abort: destination 'a repo' is not empty
  [255]

Test hg-ssh using a helper script that will restore PYTHONPATH (which might
have been cleared by a hg.exe wrapper) and invoke hg-ssh with the right
parameters:

  $ cat > ssh.sh << EOF
  > userhost="\$1"
  > SSH_ORIGINAL_COMMAND="\$2"
  > export SSH_ORIGINAL_COMMAND
  > PYTHONPATH="$PYTHONPATH"
  > export PYTHONPATH
  > python "$TESTDIR/../contrib/hg-ssh" "$TESTTMP/a repo"
  > EOF

  $ hg id --ssh "sh ssh.sh" "ssh://user@dummy/a repo"
  73649e48688a

  $ hg id --ssh "sh ssh.sh" "ssh://user@dummy/a'repo"
  remote: Illegal repository "$TESTTMP/a'repo" (glob)
  abort: no suitable response from remote hg!
  [255]

  $ hg id --ssh "sh ssh.sh" --remotecmd hacking "ssh://user@dummy/a'repo"
  remote: Illegal command "hacking -R 'a'\''repo' serve --stdio"
  abort: no suitable response from remote hg!
  [255]

  $ SSH_ORIGINAL_COMMAND="'hg' serve -R 'a'repo' --stdio" python "$TESTDIR/../contrib/hg-ssh"
  Illegal command "'hg' serve -R 'a'repo' --stdio": No closing quotation
  [255]

Test hg-ssh in read-only mode:

  $ cat > ssh.sh << EOF
  > userhost="\$1"
  > SSH_ORIGINAL_COMMAND="\$2"
  > export SSH_ORIGINAL_COMMAND
  > PYTHONPATH="$PYTHONPATH"
  > export PYTHONPATH
  > python "$TESTDIR/../contrib/hg-ssh" --read-only "$TESTTMP/remote"
  > EOF

  $ hg clone --ssh "sh ssh.sh" "ssh://user@dummy/$TESTTMP/remote" read-only-local
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 5 changes to 4 files (+1 heads)
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd read-only-local
  $ echo "baz" > bar
  $ hg ci -A -m "unpushable commit" bar
  $ hg push --ssh "sh ../ssh.sh"
  pushing to ssh://user@dummy/*/remote (glob)
  searching for changes
  remote: Permission denied
  remote: abort: pretxnopen.hg-ssh hook failed
  remote: Permission denied
  remote: pushkey-abort: prepushkey.hg-ssh hook failed
  updating 6c0482d977a3 to public failed!
  [1]

  $ cd ..

stderr from remote commands should be printed before stdout from local code (issue4336)

  $ hg clone remote stderr-ordering
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd stderr-ordering
  $ cat >> localwrite.py << EOF
  > from mercurial import exchange, extensions
  > 
  > def wrappedpush(orig, repo, *args, **kwargs):
  >     res = orig(repo, *args, **kwargs)
  >     repo.ui.write('local stdout\n')
  >     return res
  > 
  > def extsetup(ui):
  >     extensions.wrapfunction(exchange, 'push', wrappedpush)
  > EOF

  $ cat >> .hg/hgrc << EOF
  > [paths]
  > default-push = ssh://user@dummy/remote
  > [ui]
  > ssh = python "$TESTDIR/dummyssh"
  > [extensions]
  > localwrite = localwrite.py
  > EOF

  $ echo localwrite > foo
  $ hg commit -m 'testing localwrite'
  $ hg push
  pushing to ssh://user@dummy/remote
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  remote: KABOOM
  local stdout

debug output

  $ hg pull --debug ssh://user@dummy/remote
  pulling from ssh://user@dummy/remote
  running python ".*/dummyssh" user@dummy ('|")hg -R remote serve --stdio('|") (re)
  sending hello command
  sending between command
  remote: 371
  remote: capabilities: lookup changegroupsubset branchmap pushkey known getbundle unbundlehash batch streamreqs=generaldelta,revlogv1 bundle2=HG20%0Achangegroup%3D01%2C02%0Adigests%3Dmd5%2Csha1%2Csha512%0Aerror%3Dabort%2Cunsupportedcontent%2Cpushraced%2Cpushkey%0Ahgtagsfnodes%0Alistkeys%0Apushkey%0Aremote-changegroup%3Dhttp%2Chttps unbundle=HG10GZ,HG10BZ,HG10UN httpheader=1024
  remote: 1
  preparing listkeys for "bookmarks"
  sending listkeys command
  received listkey for "bookmarks": 45 bytes
  query 1; heads
  sending batch command
  searching for changes
  all remote heads known locally
  no changes found
  preparing listkeys for "phases"
  sending listkeys command
  received listkey for "phases": 15 bytes
  checking for updated bookmarks

  $ cd ..

  $ cat dummylog
  Got arguments 1:user@dummy 2:hg -R nonexistent serve --stdio
  Got arguments 1:user@dummy 2:hg -R /$TESTTMP/nonexistent serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R local-stream serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R doesnotexist serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R local serve --stdio
  Got arguments 1:user@dummy 2:hg -R $TESTTMP/local serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_NODE=a28a9d1a809cab7d4e2fde4bee738a9ede948b60 HG_NODE_LAST=a28a9d1a809cab7d4e2fde4bee738a9ede948b60 HG_SOURCE=serve HG_TXNID=TXN:* HG_URL=remote:ssh:127.0.0.1 (glob)
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_NODE=1383141674ec756a6056f6a9097618482fe0f4a6 HG_NODE_LAST=1383141674ec756a6056f6a9097618482fe0f4a6 HG_SOURCE=serve HG_TXNID=TXN:* HG_URL=remote:ssh:127.0.0.1 (glob)
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg init 'a repo'
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_NODE=65c38f4125f9602c8db4af56530cc221d93b8ef8 HG_NODE_LAST=65c38f4125f9602c8db4af56530cc221d93b8ef8 HG_SOURCE=serve HG_TXNID=TXN:* HG_URL=remote:ssh:127.0.0.1 (glob)
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio

remote hook failure is attributed to remote

  $ cat > $TESTTMP/failhook << EOF
  > def hook(ui, repo, **kwargs):
  >     ui.write('hook failure!\n')
  >     ui.flush()
  >     return 1
  > EOF

  $ echo "pretxnchangegroup.fail = python:$TESTTMP/failhook:hook" >> remote/.hg/hgrc

  $ hg -q --config ui.ssh="python $TESTDIR/dummyssh" clone ssh://user@dummy/remote hookout
  $ cd hookout
  $ touch hookfailure
  $ hg -q commit -A -m 'remote hook failure'
  $ hg --config ui.ssh="python $TESTDIR/dummyssh" push
  pushing to ssh://user@dummy/remote
  searching for changes
  remote: adding changesets
  remote: adding manifests
  remote: adding file changes
  remote: added 1 changesets with 1 changes to 1 files
  remote: hook failure!
  remote: transaction abort!
  remote: rollback completed
  remote: abort: pretxnchangegroup.fail hook failed
  [1]