tests/test-push-r.t

commandserver: add new forking server implemented without using SocketServer

SocketServer.ForkingMixIn of Python 2.x has a couple of issues, such as:

 - race condition that leads to 100% CPU usage (Python 2.6)
   https://bugs.python.org/issue21491
 - can't wait for children belonging to different process groups (Python 2.6)
 - leaves at least one zombie process (Python 2.6, 2.7)
   https://bugs.python.org/issue11109

The first two are critical because we do setpgid(0, 0) in child process to
isolate terminal signals. The last one isn't, but ForkingMixIn seems to be
doing silly. So there are two choices:

 a) backport and maintain SocketServer until we can drop support for Python 2.x
 b) replace SocketServer by simpler one and eliminate glue codes

I chose (b) because it's great time for getting rid of utterly complicated
SocketServer stuff, and preparing for future move towards prefork service.

New unixforkingservice is implemented loosely based on chg 531f8ef64be6. It
is monolithic but much simpler than SocketServer. unixservicehandler provides
customizing points for chg, and it will be shared with future prefork service.

Old unixservice class is still used by chgserver. It will be removed later.

Thanks to Jun Wu for investigating these issues.

  $ hg init test
  $ cd test
  $ hg unbundle "$TESTDIR/bundles/remote.hg"
  adding changesets
  adding manifests
  adding file changes
  added 9 changesets with 7 changes to 4 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up tip
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd ..

  $ for i in 0 1 2 3 4 5 6 7 8; do
  >    echo
  >    mkdir test-"$i"
  >    hg --cwd test-"$i" init
  >    hg -R test push -r "$i" test-"$i"
  >    cd test-"$i"
  >    hg verify
  >    cd ..
  > done
  
  pushing to test-0
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions
  
  pushing to test-1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions
  
  pushing to test-2
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 3 changesets, 3 total revisions
  
  pushing to test-3
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 4 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 4 changesets, 4 total revisions
  
  pushing to test-4
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions
  
  pushing to test-5
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 3 changesets, 3 total revisions
  
  pushing to test-6
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 5 changes to 2 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 4 changesets, 5 total revisions
  
  pushing to test-7
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 5 changesets with 6 changes to 3 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  3 files, 5 changesets, 6 total revisions
  
  pushing to test-8
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 5 changesets with 5 changes to 2 files
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 5 changesets, 5 total revisions

  $ cd test-8

  $ hg pull ../test-7
  pulling from ../test-7
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 2 changes to 3 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  4 files, 9 changesets, 7 total revisions

  $ cd ..