tests/test-worker.t

shelve: use matcher to restrict prefetch to just the modified files

Shelve currently operates by:
- make a temp commit
- identify all the bases necessary to shelve, put them in the bundle
- use exportfile to export the temp commit to the bundle ('file' here means
  "export to this fd", not "export this file")
- remove the temp commit

exportfile calls prefetchfiles, and prefetchfiles uses a matcher to restrict
what files it's going to prefetch; if it's not provided, it's alwaysmatcher.
This means that `hg shelve` in a remotefilelog repo can possibly download the
file contents of everything in the repository, even when it doesn't need to. It
luckily is restricted to the narrowspec (if there is one), but this is still a
lot of downloading that's just unnecessary, especially if there's a "smart"
VCS-aware filesystem involved.

exportfile is called with exactly one revision to emit, so we're just
restricting it to prefetching the files from that revision. The base revisions
having separate files should not be a concern since they're handled already;
example:

commit 10 is draft and modifies foo/a.txt and foo/b.txt
commit 11 is draft and modifies foo/a.txt
my working directory that I'm shelving modifies foo/b.txt

By the time we get to exportfile, commit 10 and 11 are already handled, so the
matcher only specifying foo/b.txt does not cause any problems. I verified this
by doing an `hg unbundle` on the bundle that shelve produces, and getting the
full contents of those commits back out, instead of just the files that were
modified in the shelve.

Differential Revision: https://phab.mercurial-scm.org/D5268

Test UI worker interaction

  $ cat > t.py <<EOF
  > from __future__ import absolute_import, print_function
  > import time
  > from mercurial import (
  >     error,
  >     registrar,
  >     ui as uimod,
  >     worker,
  > )
  > def abort(ui, args):
  >     if args[0] == 0:
  >         # by first worker for test stability
  >         raise error.Abort(b'known exception')
  >     return runme(ui, [])
  > def exc(ui, args):
  >     if args[0] == 0:
  >         # by first worker for test stability
  >         raise Exception('unknown exception')
  >     return runme(ui, [])
  > def runme(ui, args):
  >     for arg in args:
  >         ui.status(b'run\n')
  >         yield 1, arg
  >     time.sleep(0.1) # easier to trigger killworkers code path
  > functable = {
  >     b'abort': abort,
  >     b'exc': exc,
  >     b'runme': runme,
  > }
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command(b'test', [], b'hg test [COST] [FUNC]')
  > def t(ui, repo, cost=1.0, func=b'runme'):
  >     cost = float(cost)
  >     func = functable[func]
  >     ui.status(b'start\n')
  >     runs = worker.worker(ui, cost, func, (ui,), range(8))
  >     for n, i in runs:
  >         pass
  >     ui.status(b'done\n')
  > EOF
  $ abspath=`pwd`/t.py
  $ hg init

Run tests with worker enable by forcing a heigh cost

  $ hg --config "extensions.t=$abspath" test 100000.0
  start
  run
  run
  run
  run
  run
  run
  run
  run
  done

Run tests without worker by forcing a low cost

  $ hg --config "extensions.t=$abspath" test 0.0000001
  start
  run
  run
  run
  run
  run
  run
  run
  run
  done

#if no-windows

Known exception should be caught, but printed if --traceback is enabled

  $ hg --config "extensions.t=$abspath" --config 'worker.numcpus=8' \
  > test 100000.0 abort 2>&1
  start
  abort: known exception
  [255]

  $ hg --config "extensions.t=$abspath" --config 'worker.numcpus=8' \
  > test 100000.0 abort --traceback 2>&1 | egrep '^(SystemExit|Abort)'
  Abort: known exception
  SystemExit: 255

Traceback must be printed for unknown exceptions

  $ hg --config "extensions.t=$abspath" --config 'worker.numcpus=8' \
  > test 100000.0 exc 2>&1 | grep '^Exception'
  Exception: unknown exception

Workers should not do cleanups in all cases

  $ cat > $TESTTMP/detectcleanup.py <<EOF
  > from __future__ import absolute_import
  > import atexit
  > import os
  > import time
  > oldfork = os.fork
  > count = 0
  > parentpid = os.getpid()
  > def delayedfork():
  >     global count
  >     count += 1
  >     pid = oldfork()
  >     # make it easier to test SIGTERM hitting other workers when they have
  >     # not set up error handling yet.
  >     if count > 1 and pid == 0:
  >         time.sleep(0.1)
  >     return pid
  > os.fork = delayedfork
  > def cleanup():
  >     if os.getpid() != parentpid:
  >         os.write(1, 'should never happen\n')
  > atexit.register(cleanup)
  > EOF

  $ hg --config "extensions.t=$abspath" --config worker.numcpus=8 --config \
  > "extensions.d=$TESTTMP/detectcleanup.py" test 100000 abort
  start
  abort: known exception
  [255]

#endif