view tests/test-bundle2-multiple-changegroups.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

Create an extension to test bundle2 with multiple changegroups

  $ cat > bundle2.py <<EOF
  > """
  > """
  > from mercurial import changegroup, discovery, exchange
  > 
  > def _getbundlechangegrouppart(bundler, repo, source, bundlecaps=None,
  >                               b2caps=None, heads=None, common=None,
  >                               **kwargs):
  >     # Create two changegroups given the common changesets and heads for the
  >     # changegroup part we are being requested. Use the parent of each head
  >     # in 'heads' as intermediate heads for the first changegroup.
  >     intermediates = [repo[r].p1().node() for r in heads]
  >     outgoing = discovery.outgoing(repo, common, intermediates)
  >     cg = changegroup.makechangegroup(repo, outgoing, '01',
  >                                      source, bundlecaps=bundlecaps)
  >     bundler.newpart('output', data='changegroup1')
  >     bundler.newpart('changegroup', data=cg.getchunks())
  >     outgoing = discovery.outgoing(repo, common + intermediates, heads)
  >     cg = changegroup.makechangegroup(repo, outgoing, '01',
  >                                      source, bundlecaps=bundlecaps)
  >     bundler.newpart('output', data='changegroup2')
  >     bundler.newpart('changegroup', data=cg.getchunks())
  > 
  > def _pull(repo, *args, **kwargs):
  >   pullop = _orig_pull(repo, *args, **kwargs)
  >   repo.ui.write('pullop.cgresult is %d\n' % pullop.cgresult)
  >   return pullop
  > 
  > _orig_pull = exchange.pull
  > exchange.pull = _pull
  > exchange.getbundle2partsmapping['changegroup'] = _getbundlechangegrouppart
  > EOF

  $ cat >> $HGRCPATH << EOF
  > [ui]
  > logtemplate={rev}:{node|short} {phase} {author} {bookmarks} {desc|firstline}
  > EOF

Start with a simple repository with a single commit

  $ hg init repo
  $ cd repo
  $ cat > .hg/hgrc << EOF
  > [extensions]
  > bundle2=$TESTTMP/bundle2.py
  > EOF

  $ echo A > A
  $ hg commit -A -m A -q
  $ cd ..

Clone

  $ hg clone -q repo clone

Add two linear commits

  $ cd repo
  $ echo B > B
  $ hg commit -A -m B -q
  $ echo C > C
  $ hg commit -A -m C -q

  $ cd ../clone
  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > pretxnchangegroup = sh -c "printenv.py pretxnchangegroup"
  > changegroup = sh -c "printenv.py changegroup"
  > incoming = sh -c "printenv.py incoming"
  > EOF

Pull the new commits in the clone

  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56 HG_NODE_LAST=27547f69f25460a52fff66ad004e58da7ad3fb56 HG_PENDING=$TESTTMP/clone HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757 HG_NODE_LAST=f838bfaca5c7226600ebcfd84f3c3c13a28d3757 HG_PENDING=$TESTTMP/clone HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  new changesets 27547f69f254:f838bfaca5c7
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56 HG_NODE_LAST=27547f69f25460a52fff66ad004e58da7ad3fb56 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=27547f69f25460a52fff66ad004e58da7ad3fb56 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757 HG_NODE_LAST=f838bfaca5c7226600ebcfd84f3c3c13a28d3757 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=f838bfaca5c7226600ebcfd84f3c3c13a28d3757 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  pullop.cgresult is 1
  (run 'hg update' to get a working copy)
  $ hg update
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg log -G
  @  2:f838bfaca5c7 public test  C
  |
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A
  
Add more changesets with multiple heads to the original repository

  $ cd ../repo
  $ echo D > D
  $ hg commit -A -m D -q
  $ hg up -r 1
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo E > E
  $ hg commit -A -m E -q
  $ echo F > F
  $ hg commit -A -m F -q
  $ hg up -r 1
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo G > G
  $ hg commit -A -m G -q
  $ hg up -r 3
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo H > H
  $ hg commit -A -m H -q
  $ hg log -G
  @  7:5cd59d311f65 draft test  H
  |
  | o  6:1d14c3ce6ac0 draft test  G
  | |
  | | o  5:7f219660301f draft test  F
  | | |
  | | o  4:8a5212ebc852 draft test  E
  | |/
  o |  3:b3325c91a4d9 draft test  D
  | |
  o |  2:f838bfaca5c7 draft test  C
  |/
  o  1:27547f69f254 draft test  B
  |
  o  0:4a2df7238c3b draft test  A
  
New heads are reported during transfer and properly accounted for in
pullop.cgresult

  $ cd ../clone
  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files (+1 heads)
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e HG_NODE_LAST=8a5212ebc8527f9fb821601504794e3eb11a1ed3 HG_PENDING=$TESTTMP/clone HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+1 heads)
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46 HG_NODE_LAST=5cd59d311f6508b8e0ed28a266756c859419c9f1 HG_PENDING=$TESTTMP/clone HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  new changesets b3325c91a4d9:5cd59d311f65
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e HG_NODE_LAST=8a5212ebc8527f9fb821601504794e3eb11a1ed3 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=b3325c91a4d916bcc4cdc83ea3fe4ece46a42f6e HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=8a5212ebc8527f9fb821601504794e3eb11a1ed3 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46 HG_NODE_LAST=5cd59d311f6508b8e0ed28a266756c859419c9f1 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=7f219660301fe4c8a116f714df5e769695cc2b46 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=1d14c3ce6ac0582d2809220d33e8cd7a696e0156 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=5cd59d311f6508b8e0ed28a266756c859419c9f1 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  pullop.cgresult is 3
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg log -G
  o  7:5cd59d311f65 public test  H
  |
  | o  6:1d14c3ce6ac0 public test  G
  | |
  | | o  5:7f219660301f public test  F
  | | |
  | | o  4:8a5212ebc852 public test  E
  | |/
  o |  3:b3325c91a4d9 public test  D
  | |
  @ |  2:f838bfaca5c7 public test  C
  |/
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A
  
Removing a head from the original repository by merging it

  $ cd ../repo
  $ hg merge -r 6 -q
  $ hg commit -m Merge
  $ echo I > I
  $ hg commit -A -m H -q
  $ hg log -G
  @  9:9d18e5bd9ab0 draft test  H
  |
  o    8:71bd7b46de72 draft test  Merge
  |\
  | o  7:5cd59d311f65 draft test  H
  | |
  o |  6:1d14c3ce6ac0 draft test  G
  | |
  | | o  5:7f219660301f draft test  F
  | | |
  +---o  4:8a5212ebc852 draft test  E
  | |
  | o  3:b3325c91a4d9 draft test  D
  | |
  | o  2:f838bfaca5c7 draft test  C
  |/
  o  1:27547f69f254 draft test  B
  |
  o  0:4a2df7238c3b draft test  A
  
Removed heads are reported during transfer and properly accounted for in
pullop.cgresult

  $ cd ../clone
  $ hg pull
  pulling from $TESTTMP/repo
  searching for changes
  remote: changegroup1
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (-1 heads)
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4 HG_NODE_LAST=71bd7b46de72e69a32455bf88d04757d542e6cf4 HG_PENDING=$TESTTMP/clone HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  remote: changegroup2
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  pretxnchangegroup hook: HG_HOOKNAME=pretxnchangegroup HG_HOOKTYPE=pretxnchangegroup HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84 HG_NODE_LAST=9d18e5bd9ab09337802595d49f1dad0c98df4d84 HG_PENDING=$TESTTMP/clone HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  new changesets 71bd7b46de72:9d18e5bd9ab0
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4 HG_NODE_LAST=71bd7b46de72e69a32455bf88d04757d542e6cf4 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=71bd7b46de72e69a32455bf88d04757d542e6cf4 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  changegroup hook: HG_HOOKNAME=changegroup HG_HOOKTYPE=changegroup HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84 HG_NODE_LAST=9d18e5bd9ab09337802595d49f1dad0c98df4d84 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  incoming hook: HG_HOOKNAME=incoming HG_HOOKTYPE=incoming HG_NODE=9d18e5bd9ab09337802595d49f1dad0c98df4d84 HG_PHASES_MOVED=1 HG_SOURCE=pull HG_TXNID=TXN:$ID$ HG_URL=file:$TESTTMP/repo
  pullop.cgresult is -2
  (run 'hg update' to get a working copy)
  $ hg log -G
  o  9:9d18e5bd9ab0 public test  H
  |
  o    8:71bd7b46de72 public test  Merge
  |\
  | o  7:5cd59d311f65 public test  H
  | |
  o |  6:1d14c3ce6ac0 public test  G
  | |
  | | o  5:7f219660301f public test  F
  | | |
  +---o  4:8a5212ebc852 public test  E
  | |
  | o  3:b3325c91a4d9 public test  D
  | |
  | @  2:f838bfaca5c7 public test  C
  |/
  o  1:27547f69f254 public test  B
  |
  o  0:4a2df7238c3b public test  A