view tests/test-lfs-largefiles.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 tests the interaction between the largefiles and lfs extensions, and
conversion from largefiles -> lfs.

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > largefiles =
  > 
  > [lfs]
  > # standin files are 41 bytes.  Stay bigger for clarity.
  > threshold = 42
  > EOF

Setup a repo with a normal file and a largefile, above and below the lfs
threshold to test lfconvert.  *.txt start life as a normal file; *.bin start as
an lfs/largefile.

  $ hg init largefiles
  $ cd largefiles
  $ echo 'normal' > normal.txt
  $ echo 'normal above lfs threshold 0000000000000000000000000' > lfs.txt
  $ hg ci -Am 'normal.txt'
  adding lfs.txt
  adding normal.txt
  $ echo 'largefile' > large.bin
  $ echo 'largefile above lfs threshold 0000000000000000000000' > lfs.bin
  $ hg add --large large.bin lfs.bin
  $ hg ci -m 'add largefiles'

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > lfs =
  > EOF

Add an lfs file and normal file that collide with files on the other branch.
large.bin is added as a normal file, and is named as such only to clash with the
largefile on the other branch.

  $ hg up -q '.^'
  $ echo 'below lfs threshold' > large.bin
  $ echo 'lfs above the lfs threshold for length 0000000000000' > lfs.bin
  $ hg ci -Am 'add with lfs extension'
  adding large.bin
  adding lfs.bin
  created new head

  $ hg log -G
  @  changeset:   2:e989d0fa3764
  |  tag:         tip
  |  parent:      0:29361292f54d
  |  user:        test
  |  date:        Thu Jan 01 00:00:00 1970 +0000
  |  summary:     add with lfs extension
  |
  | o  changeset:   1:6513aaab9ca0
  |/   user:        test
  |    date:        Thu Jan 01 00:00:00 1970 +0000
  |    summary:     add largefiles
  |
  o  changeset:   0:29361292f54d
     user:        test
     date:        Thu Jan 01 00:00:00 1970 +0000
     summary:     normal.txt
  
--------------------------------------------------------------------------------
Merge largefiles into lfs branch

The largefiles extension will prompt to use the normal or largefile when merged
into the lfs files.  `hg manifest` will show standins if present.  They aren't,
because largefiles merge doesn't merge content.  If it did, selecting (n)ormal
would convert to lfs on commit, if appropriate.

BUG: Largefiles isn't running the merge tool, like when two lfs files are
merged.  This is probably by design, but it should probably at least prompt if
content should be taken from (l)ocal or (o)ther as well.

  $ hg --config ui.interactive=True merge 6513aaab9ca0 <<EOF
  > n
  > n
  > EOF
  remote turned local normal file large.bin into a largefile
  use (l)argefile or keep (n)ormal file? n
  remote turned local normal file lfs.bin into a largefile
  use (l)argefile or keep (n)ormal file? n
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m 'merge lfs with largefiles -> normal'
  $ hg manifest
  large.bin
  lfs.bin
  lfs.txt
  normal.txt

The merged lfs.bin resolved to lfs because the (n)ormal option was picked.  The
lfs.txt file is unchanged by the merge, because it was added before lfs was
enabled, and the content didn't change.
  $ hg debugdata lfs.bin 0
  version https://git-lfs.github.com/spec/v1
  oid sha256:81c7492b2c05e130431f65a87651b54a30c5da72c99ce35a1e9b9872a807312b
  size 53
  x-is-binary 0
  $ hg debugdata lfs.txt 0
  normal above lfs threshold 0000000000000000000000000

Another filelog entry is NOT made by the merge, so nothing is committed as lfs.
  $ hg log -r . -T '{join(lfs_files, ", ")}\n'
  

Replay the last merge, but pick (l)arge this time.  The manifest will show any
standins.

  $ hg up -Cq e989d0fa3764

  $ hg --config ui.interactive=True merge 6513aaab9ca0 <<EOF
  > l
  > l
  > EOF
  remote turned local normal file large.bin into a largefile
  use (l)argefile or keep (n)ormal file? l
  remote turned local normal file lfs.bin into a largefile
  use (l)argefile or keep (n)ormal file? l
  getting changed largefiles
  2 largefiles updated, 0 removed
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m 'merge lfs with largefiles -> large'
  created new head
  $ hg manifest
  .hglf/large.bin
  .hglf/lfs.bin
  lfs.txt
  normal.txt

--------------------------------------------------------------------------------
Merge lfs into largefiles branch

  $ hg up -Cq 6513aaab9ca0
  $ hg --config ui.interactive=True merge e989d0fa3764 <<EOF
  > n
  > n
  > EOF
  remote turned local largefile large.bin into a normal file
  keep (l)argefile or use (n)ormal file? n
  remote turned local largefile lfs.bin into a normal file
  keep (l)argefile or use (n)ormal file? n
  getting changed largefiles
  0 largefiles updated, 0 removed
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m 'merge largefiles with lfs -> normal'
  created new head
  $ hg manifest
  large.bin
  lfs.bin
  lfs.txt
  normal.txt

The merged lfs.bin got converted to lfs because the (n)ormal option was picked.
The lfs.txt file is unchanged by the merge, because it was added before lfs was
enabled.
  $ hg debugdata lfs.bin 0
  version https://git-lfs.github.com/spec/v1
  oid sha256:81c7492b2c05e130431f65a87651b54a30c5da72c99ce35a1e9b9872a807312b
  size 53
  x-is-binary 0
  $ hg debugdata lfs.txt 0
  normal above lfs threshold 0000000000000000000000000

Another filelog entry is NOT made by the merge, so nothing is committed as lfs.
  $ hg log -r . -T '{join(lfs_files, ", ")}\n'
  

Replay the last merge, but pick (l)arge this time.  The manifest will show the
standins.

  $ hg up -Cq 6513aaab9ca0

  $ hg --config ui.interactive=True merge e989d0fa3764 <<EOF
  > l
  > l
  > EOF
  remote turned local largefile large.bin into a normal file
  keep (l)argefile or use (n)ormal file? l
  remote turned local largefile lfs.bin into a normal file
  keep (l)argefile or use (n)ormal file? l
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m 'merge largefiles with lfs -> large'
  created new head
  $ hg manifest
  .hglf/large.bin
  .hglf/lfs.bin
  lfs.txt
  normal.txt

--------------------------------------------------------------------------------

When both largefiles and lfs are configured to add by size, the tie goes to
largefiles since it hooks cmdutil.add() and lfs hooks the filelog write in the
commit.  By the time the commit occurs, the tracked file is smaller than the
threshold (assuming it is > 41, so the standins don't become lfs objects).

  $ $PYTHON -c 'import sys ; sys.stdout.write("y\n" * 1048576)' > large_by_size.bin
  $ hg --config largefiles.minsize=1 ci -Am 'large by size'
  adding large_by_size.bin as a largefile
  $ hg manifest
  .hglf/large.bin
  .hglf/large_by_size.bin
  .hglf/lfs.bin
  lfs.txt
  normal.txt

  $ hg rm large_by_size.bin
  $ hg ci -m 'remove large_by_size.bin'

Largefiles doesn't do anything special with diff, so it falls back to diffing
the standins.  Extdiff also is standin based comparison.  Diff and extdiff both
work on the original file for lfs objects.

Largefile -> lfs transition
  $ hg diff -r 1 -r 3
  diff -r 6513aaab9ca0 -r dcc5ce63e252 .hglf/large.bin
  --- a/.hglf/large.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +0,0 @@
  -cef9a458373df9b0743a0d3c14d0c66fb19b8629
  diff -r 6513aaab9ca0 -r dcc5ce63e252 .hglf/lfs.bin
  --- a/.hglf/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +0,0 @@
  -557fb6309cef935e1ac2c8296508379e4b15a6e6
  diff -r 6513aaab9ca0 -r dcc5ce63e252 large.bin
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/large.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +below lfs threshold
  diff -r 6513aaab9ca0 -r dcc5ce63e252 lfs.bin
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +lfs above the lfs threshold for length 0000000000000

lfs -> largefiles transition
  $ hg diff -r 2 -r 6
  diff -r e989d0fa3764 -r 95e1e80325c8 .hglf/large.bin
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/.hglf/large.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +cef9a458373df9b0743a0d3c14d0c66fb19b8629
  diff -r e989d0fa3764 -r 95e1e80325c8 .hglf/lfs.bin
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/.hglf/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,1 @@
  +557fb6309cef935e1ac2c8296508379e4b15a6e6
  diff -r e989d0fa3764 -r 95e1e80325c8 large.bin
  --- a/large.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +0,0 @@
  -below lfs threshold
  diff -r e989d0fa3764 -r 95e1e80325c8 lfs.bin
  --- a/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +0,0 @@
  -lfs above the lfs threshold for length 0000000000000

A largefiles repo can be converted to lfs.  The lfconvert command uses the
convert extension under the hood with --to-normal.  So the --config based
parameters are available, but not --authormap, --branchmap, etc.

  $ cd ..
  $ hg lfconvert --to-normal largefiles nolargefiles 2>&1
  initializing destination nolargefiles
  0 additional largefiles cached
  scanning source...
  sorting...
  converting...
  8 normal.txt
  7 add largefiles
  6 add with lfs extension
  5 merge lfs with largefiles -> normal
  4 merge lfs with largefiles -> large
  3 merge largefiles with lfs -> normal
  2 merge largefiles with lfs -> large
  1 large by size
  0 remove large_by_size.bin
  $ cd nolargefiles

The requirement is added to the destination repo, and the extension is enabled
locally.

  $ cat .hg/requires
  dotencode
  fncache
  generaldelta
  lfs
  revlogv1
  store
  $ hg config --debug extensions | grep lfs
  $TESTTMP/nolargefiles/.hg/hgrc:*: extensions.lfs= (glob)

  $ hg log -r 'all()' -G -T '{rev} {join(lfs_files, ", ")} ({desc})\n'
  o  8  (remove large_by_size.bin)
  |
  o  7 large_by_size.bin (large by size)
  |
  o    6  (merge largefiles with lfs -> large)
  |\
  +---o  5  (merge largefiles with lfs -> normal)
  | |/
  +---o  4 lfs.bin (merge lfs with largefiles -> large)
  | |/
  +---o  3  (merge lfs with largefiles -> normal)
  | |/
  | o  2 lfs.bin (add with lfs extension)
  | |
  o |  1 lfs.bin (add largefiles)
  |/
  o  0 lfs.txt (normal.txt)
  
  $ hg debugdata lfs.bin 0
  version https://git-lfs.github.com/spec/v1
  oid sha256:2172a5bd492dd41ec533b9bb695f7691b6351719407ac797f0ccad5348c81e62
  size 53
  x-is-binary 0
  $ hg debugdata lfs.bin 1
  version https://git-lfs.github.com/spec/v1
  oid sha256:81c7492b2c05e130431f65a87651b54a30c5da72c99ce35a1e9b9872a807312b
  size 53
  x-is-binary 0
  $ hg debugdata lfs.bin 2
  version https://git-lfs.github.com/spec/v1
  oid sha256:2172a5bd492dd41ec533b9bb695f7691b6351719407ac797f0ccad5348c81e62
  size 53
  x-is-binary 0
  $ hg debugdata lfs.bin 3
  abort: invalid revision identifier 3
  [255]

No diffs when comparing merge and p1 that kept p1's changes.  Diff of lfs to
largefiles no longer operates in standin files.

  $ hg diff -r 2:3
  $ hg diff -r 2:6
  diff -r e989d0fa3764 -r 752e3a0d8488 large.bin
  --- a/large.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ b/large.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -below lfs threshold
  +largefile
  diff -r e989d0fa3764 -r 752e3a0d8488 lfs.bin
  --- a/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  +++ b/lfs.bin	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,1 +1,1 @@
  -lfs above the lfs threshold for length 0000000000000
  +largefile above lfs threshold 0000000000000000000000