view tests/test-issue2137.t @ 52176:72bc29f01570

revlog: add glue to use a pure-Rust VFS

This will save us a lot of calling back into Python, which is always
horribly expensive.

We are now faster in all benchmarked cases except for `log --patch`
specifically on mozilla-try. Fixing this will happen in a later patch.

```
### data-env-vars.name            = mercurial-devel-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.cat
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.files      = all-root
  # benchmark.variants.output     = plain
  # benchmark.variants.rev        = tip
e679697a6ca4: 1.760765  ~~~~~
5559d7e63ec3: 1.555513  (-11.66%, -0.21)
### data-env-vars.name            = mozilla-try-2024-03-26-ds2-pnm
  # benchmark.name                = hg.command.cat
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.files      = all-root
  # benchmark.variants.output     = plain
  # benchmark.variants.rev        = tip
e679697a6ca4: 62.848869  ~~~~~
5559d7e63ec3: 58.113051   (-7.54%, -4.74)
### data-env-vars.name            = mozilla-try-2024-03-26-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
  # benchmark.variants.rev        = none
e679697a6ca4: 3.173532  ~~~~~
5559d7e63ec3: 3.543591  (+11.66%, +0.37)
### data-env-vars.name            = mozilla-try-2024-03-26-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = none
e679697a6ca4: 1.214698  ~~~~~
5559d7e63ec3: 1.192478   (-1.83%, -0.02)
### data-env-vars.name            = mozilla-unified-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.cat
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.files      = all-root
  # benchmark.variants.output     = plain
  # benchmark.variants.rev        = tip
e679697a6ca4: 56.205474  ~~~~~
5559d7e63ec3: 51.520074   (-8.34%, -4.69)
### data-env-vars.name            = mozilla-unified-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
  # benchmark.variants.rev        = none
e679697a6ca4: 2.105419  ~~~~~
5559d7e63ec3: 2.051849   (-2.54%, -0.05)
### data-env-vars.name            = mozilla-unified-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = none
e679697a6ca4: 0.309960  ~~~~~
5559d7e63ec3: 0.299035   (-3.52%, -0.01)
### data-env-vars.name            = tryton-public-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.cat
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.files      = all-root
  # benchmark.variants.output     = plain
  # benchmark.variants.rev        = tip
e679697a6ca4: 1.849832  ~~~~~
5559d7e63ec3: 1.805076   (-2.42%, -0.04)
### data-env-vars.name            = tryton-public-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 10
  # benchmark.variants.patch      = yes
  # benchmark.variants.rev        = none
e679697a6ca4: 0.289521  ~~~~~
5559d7e63ec3: 0.279889   (-3.33%, -0.01)
### data-env-vars.name            = tryton-public-2024-03-22-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = none
e679697a6ca4: 0.332270  ~~~~~
5559d7e63ec3: 0.323324   (-2.69%, -0.01)
```

https://bz.mercurial-scm.org/2137

Setup:

create a little extension that has 3 side-effects:
1) ensure changelog data is not inlined
2) make revlog to use lazyparser
3) test that repo.lookup() works
1 and 2 are preconditions for the bug; 3 is the bug.

  $ cat > commitwrapper.py <<EOF
  > from mercurial import extensions, node, revlog
  > 
  > def reposetup(ui, repo):
  >     class wraprepo(repo.__class__):
  >         def commit(self, *args, **kwargs):
  >             result = super(wraprepo, self).commit(*args, **kwargs)
  >             tip1 = node.short(repo.changelog.tip())
  >             tip2 = node.short(repo.lookup(tip1))
  >             assert tip1 == tip2
  >             ui.write(b'new tip: %s\n' % tip1)
  >             return result
  >     repo.__class__ = wraprepo
  > 
  > def extsetup(ui):
  >     revlog._maxinline = 8             # split out 00changelog.d early
  >     revlog._prereadsize = 8           # use revlog.lazyparser
  > EOF

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > commitwrapper = `pwd`/commitwrapper.py
  > EOF

  $ hg init repo1
  $ cd repo1
  $ echo a > a
  $ hg commit -A -m'add a with a long commit message to make the changelog a bit bigger'
  adding a
  new tip: 553596fad57b

Test that new changesets are visible to repo.lookup():

  $ echo a >> a
  $ hg commit -m'one more commit to demonstrate the bug'
  new tip: 799ae3599e0e

  $ hg tip
  changeset:   1:799ae3599e0e
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     one more commit to demonstrate the bug
  

  $ cd ..