tests/test-logtoprocess.t

update: add a Rust fast-path when updating from null (and clean)

This case is easy to detect and we have all we need to generate a valid
working copy and dirstate entirely in Rust, which speeds things up
considerably:

On my machine updating a repo of ~300k files goes from 10.00s down to 4.2s,
all while consuming 50% less system time, with all caches hot.
Something to note is that further improvements will probably happen
with the upcoming `InnerRevlog` series that does smarter
mmap hanlding, especially for filelogs.

Here are benchmark numbers on a machine with only 4 cores (and no SMT enabled)

```
### data-env-vars.name               = heptapod-public-2024-03-25-ds2-pnm
  # benchmark.name                   = hg.command.update
  # bin-env-vars.hg.py-re2-module    = default
  # bin-env-vars.hg.changeset.node   = <this change>
  # benchmark.variants.atomic-update = no
  # benchmark.variants.scenario      = null-to-tip
  # benchmark.variants.worker        = default
default: 5.328762  ~~~~~
rust: 1.308654  (-75.44%, -4.02)
### data-env-vars.name               = mercurial-devel-2024-03-22-ds2-pnm
  # benchmark.name                   = hg.command.update
  # bin-env-vars.hg.py-re2-module    = default
  # bin-env-vars.hg.changeset.node   = <this change>
  # benchmark.variants.atomic-update = no
  # benchmark.variants.scenario      = null-to-tip
  # benchmark.variants.worker        = default
default: 1.693271  ~~~~~
rust: 1.151053  (-32.02%, -0.54)
### data-env-vars.name               = mozilla-unified-2024-03-22-ds2-pnm
  # benchmark.name                   = hg.command.update
  # bin-env-vars.hg.py-re2-module    = default
  # bin-env-vars.hg.changeset.node   = <this change>
  # benchmark.variants.atomic-update = no
  # benchmark.variants.scenario      = null-to-tip
  # benchmark.variants.worker        = default
default: 38.901613  ~~~~~
rust: 11.637880 (-70.08%, -27.26)
### data-env-vars.name               = netbsd-xsrc-public-2024-09-19-ds2-pnm
  # benchmark.name                   = hg.command.update
  # bin-env-vars.hg.py-re2-module    = default
  # bin-env-vars.hg.changeset.node   = <this change>
  # benchmark.variants.atomic-update = no
  # benchmark.variants.scenario      = null-to-tip
  # benchmark.variants.worker        = default
default: 4.793727  ~~~~~
rust: 1.505905  (-68.59%, -3.29)
```

#require no-windows

ATTENTION: logtoprocess runs commands asynchronously. Be sure to append "| cat"
to hg commands, to wait for the output, if you want to test its output.
Otherwise the test will be flaky.

Test if logtoprocess correctly captures command-related log calls.

  $ hg init
  $ cat > $TESTTMP/foocommand.py << EOF
  > from mercurial import registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > configtable = {}
  > configitem = registrar.configitem(configtable)
  > configitem(b'logtoprocess', b'foo',
  >     default=None,
  > )
  > @command(b'foobar', [])
  > def foo(ui, repo):
  >     ui.log(b'foo', b'a message: %s\n', b'spam')
  > EOF
  $ cp $HGRCPATH $HGRCPATH.bak
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > logtoprocess=
  > foocommand=$TESTTMP/foocommand.py
  > [logtoprocess]
  > command=(echo 'logtoprocess command output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1") > $TESTTMP/command.log
  > commandfinish=(echo 'logtoprocess commandfinish output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1";
  >     echo "canonical: \$OPT_CANONICAL_COMMAND") > $TESTTMP/commandfinish.log
  > foo=(echo 'logtoprocess foo output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1") > $TESTTMP/foo.log
  > EOF

Running a command triggers both a ui.log('command') and a
ui.log('commandfinish') call. The foo command also uses ui.log.

Use sort to avoid ordering issues between the various processes we spawn:
  $ hg fooba
  $ sleep 1
  $ cat $TESTTMP/command.log | sort
  
  command
  fooba
  logtoprocess command output:

#if no-chg
  $ cat $TESTTMP/commandfinish.log | sort
  
  canonical: foobar
  commandfinish
  fooba exited 0 after * seconds (glob)
  logtoprocess commandfinish output:
  $ cat $TESTTMP/foo.log | sort
  
  a message: spam
  foo
  logtoprocess foo output:
#endif

Confirm that logging blocked time catches stdio properly:
  $ cp $HGRCPATH.bak $HGRCPATH
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > logtoprocess=
  > pager=
  > [logtoprocess]
  > uiblocked=echo "\$EVENT stdio \$OPT_STDIO_BLOCKED ms command \$OPT_COMMAND_DURATION ms" > $TESTTMP/uiblocked.log
  > [ui]
  > logblockedtimes=True
  > EOF

  $ hg log
  $ sleep 1
  $ cat $TESTTMP/uiblocked.log
  uiblocked stdio [0-9]+.[0-9]* ms command [0-9]+.[0-9]* ms (re)

Try to confirm that pager wait on logtoprocess:

Add a script that waits on a file to appear. If the script is awaited by hg,
the script will die after the timeout before we could touch the file and the
resulting file will not exist. If not, we will touch the file and see it.

  $ cat >> fakepager.py <<EOF
  > import sys
  > printed = False
  > for line in sys.stdin:
  >     sys.stdout.write(line)
  >     printed = True
  > if not printed:
  >     sys.stdout.write('paged empty output!\n')
  > EOF

  $ cat > $TESTTMP/wait-output.sh << EOF
  > #!/bin/sh
  > set -eu
  > "$RUNTESTDIR/testlib/wait-on-file" 10 "$TESTTMP/wait-for-touched"
  > touch "$TESTTMP/touched"
  > EOF
  $ chmod +x $TESTTMP/wait-output.sh

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > logtoprocess=
  > pager=
  > [pager]
  > pager = "$PYTHON" $TESTTMP/fakepager.py
  > [logtoprocess]
  > commandfinish=$TESTTMP/wait-output.sh
  > EOF
  $ hg version -q --pager=always
  Mercurial Distributed SCM (version *) (glob)
  $ touch $TESTTMP/wait-for-touched
  $ "$RUNTESTDIR/testlib/wait-on-file" 5 "$TESTTMP/touched"
  $ test -f $TESTTMP/touched && echo "SUCCESS Pager is not waiting on ltp" || echo "FAIL Pager is waiting on ltp"
  SUCCESS Pager is not waiting on ltp