view tests/test-ssh-bundle1.t @ 35569:964212780daf

rust: implementation of `hg`

This commit provides a mostly-working implementation of the
`hg` script in Rust along with scaffolding to support Rust in
the repository.

If you are familiar with Rust, the contents of the added rust/
directory should be pretty straightforward. We create an "hgcli"
package that implements a binary application to run Mercurial.
The output of this package is an "hg" binary.

Our Rust `hg` (henceforth "rhg") essentially is a port of the existing
`hg` Python script. The main difference is the creation of the embedded
CPython interpreter is handled by the binary itself instead of relying
on the shebang. In that sense, rhg is more similar to the "exe wrapper"
we currently use on Windows. However, unlike the exe wrapper, rhg does
not call the `hg` Python script. Instead, it uses the CPython APIs to
import mercurial modules and call appropriate functions. The amount of
code here is surprisingly small.

It is my intent to replace the existing C-based exe wrapper with rhg.
Preferably in the next Mercurial release. This should be achievable -
at least for some Mercurial distributions. The future/timeline for
rhg on other platforms is less clear. We already ship a hg.exe on
Windows. So if we get the quirks with Rust worked out, shipping a
Rust-based hg.exe should hopefully not be too contentious.

Now onto the implementation.

We're using python27-sys and the cpython crates for talking to the
CPython API. We currently don't use too much functionality of the
cpython crate and could have probably cut it out. However, it does
provide a reasonable abstraction over unsafe {} CPython function
calls. While we still have our fair share of those, at least we're
not dealing with too much refcounting, error checking, etc. So I
think the use of the cpython crate is justified. Plus, there is
not-yet-implemented functionality that could benefit from cpython. I
see our use of this crate only increasing.

The cpython and python27-sys crates are not without their issues.
The cpython crate didn't seem to account for the embedding use case
in its design. Instead, it seems to assume that you are building
a Python extension. It is making some questionable decisions around
certain CPython APIs. For example, it insists that
PyEval_ThreadsInitialized() is called and that the Python code
likely isn't the main thread in the underlying application. It
is also missing some functionality that is important for embedded
use cases (such as exporting the path to the Python interpreter
from its build script). After spending several hours trying to
wrangle python27-sys and cpython, I gave up and forked the project
on GitHub. Our Cargo.toml tracks this fork. I'm optimistic that
the upstream project will accept our contributions and we can
eventually unfork.

There is a non-trivial amount of code in our custom Cargo build
script. Our build.rs (which is called as part of building the hgcli
crate):

* Validates that the Python interpreter that was detected by the
  python27-sys crate provides a shared library (we only support
  shared library linking at this time - although this restriction
  could be loosened).
* Validates that the Python is built with UCS-4 support. This ensures
  maximum Unicode compatibility.
* Exports variables to the crate build allowing the built crate to e.g.
  find the path to the Python interpreter.

The produced rhg should be considered alpha quality. There are several
known deficiencies. Many of these are documented with inline TODOs.

Probably the biggest limitation of rhg is that it assumes it is
running from the ./rust/target/<target> directory of a source
distribution. So, rhg is currently not very practical for real-world
use. But, if you can `cargo build` it, running the binary *should*
yield a working Mercurial CLI.

In order to support using rhg with the test harness, we needed to hack
up run-tests.py so the path to Mercurial's Python files is set properly.
The change is extremely hacky and is only intended to be a stop-gap
until the test harness gains first-class support for installing rhg.
This will likely occur after we support running rhg outside the
source directory.

Despite its officially alpha quality, rhg copes extremely well with
the test harness (at least on Linux). Using
`run-tests.py --with-hg ../rust/target/debug/hg`, I only encounter
the following failures:

* test-run-tests.t -- Warnings emitted about using an unexpected
  Mercurial library. This is due to the hacky nature of setting the
  Python directory when run-tests.py detected rhg.
* test-devel-warnings.t -- Expected stack trace missing frame for `hg`
  (This is expected since we no longer have an `hg` script!)
* test-convert.t -- Test running `$PYTHON "$BINDIR"/hg`, which obviously
  assumes `hg` is a Python script.
* test-merge-tools.t -- Same assumption about `hg` being executable with
  Python.
* test-http-bad-server.t -- Seeing exit code 255 instead of 1 around
  line 358.
* test-blackbox.t -- Exit code 255 instead of 1.
* test-basic.t -- Exit code 255 instead of 1.

It certainly looks like we have a bug around exit code handling. I
don't think it is severe enough to hold up review and landing of this
initial implementation. Perfect is the enemy of good.

Differential Revision: https://phab.mercurial-scm.org/D1581

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 = sh -c "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\"" --stream 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\"" --stream 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
  new changesets 1160648e36ce:ad076bfb429d
  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
  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > changegroup = sh -c "printenv.py changegroup-in-local 0 ../dummylog"
  > EOF

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)
  new changesets 1160648e36ce:1383141674ec
  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"
  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)
  new changesets 1160648e36ce:1383141674ec
  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 .* ".*/dummyssh" ['"]user@dummy['"] ('|")hg -R remote serve --stdio('|") (re)
  sending hello command
  sending between command
  remote: 384
  remote: capabilities: lookup changegroupsubset branchmap pushkey known getbundle unbundlehash batch streamreqs=generaldelta,revlogv1 $USUAL_BUNDLE2_CAPS$ unbundle=HG10GZ,HG10BZ,HG10UN
  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 $TESTTMP/local serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=a28a9d1a809cab7d4e2fde4bee738a9ede948b60 HG_NODE_LAST=a28a9d1a809cab7d4e2fde4bee738a9ede948b60 HG_SOURCE=serve HG_TXNID=TXN:$ID$ HG_URL=remote:ssh:$LOCALIP
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=1383141674ec756a6056f6a9097618482fe0f4a6 HG_NODE_LAST=1383141674ec756a6056f6a9097618482fe0f4a6 HG_SOURCE=serve HG_TXNID=TXN:$ID$ HG_URL=remote:ssh:$LOCALIP
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  Got arguments 1:user@dummy 2:hg init 'a repo'
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R 'a repo' serve --stdio
  Got arguments 1:user@dummy 2:hg -R remote serve --stdio
  changegroup-in-remote hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=65c38f4125f9602c8db4af56530cc221d93b8ef8 HG_NODE_LAST=65c38f4125f9602c8db4af56530cc221d93b8ef8 HG_SOURCE=serve HG_TXNID=TXN:$ID$ HG_URL=remote:ssh:$LOCALIP
  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]

abort during pull is properly reported as such

  $ echo morefoo >> ../remote/foo
  $ hg -R ../remote commit --message "more foo to be pulled"
  $ cat >> ../remote/.hg/hgrc << EOF
  > [extensions]
  > crash = ${TESTDIR}/crashgetbundler.py
  > EOF
  $ hg --config ui.ssh="\"$PYTHON\" $TESTDIR/dummyssh" pull
  pulling from ssh://user@dummy/remote
  searching for changes
  adding changesets
  remote: abort: this is an exercise
  transaction abort!
  rollback completed
  abort: stream ended unexpectedly (got 0 bytes, expected 4)
  [255]