master: t5800-remote-helpers.sh hangs on test "pulling from remote remote"

[Stefano Lattarini <stefano.lattarini@gmail.com>]

The test 't5800-remote-helpers.sh' hangs on my Linux desktop (where I have
installed a custom simple-minded firewall based on iptables).  This does
not happen on remote systems I use for testing, so I guess the problem
lies with my machine.  Still, having the test to hang is unnecessarily
harsh and user-unfriendly IMHO, and it would be better to detect the
situation and SKIP or FAIL the affected test cases instead.

For reference, here is the output of the test 't5800-remote-helpers.sh' run
with the '-v' option:

-*-*-

Initialized empty Git repository in /devel/stefano/src/git/t/trash directory.t5800-remote-helpers/.git/
expecting success:
        git init --bare server/.git &&
        git clone server public &&
        (cd public &&
         echo content >file &&
         git add file &&
         git commit -m one &&
         git push origin master)

Initialized empty Git repository in /devel/stefano/src/git/t/trash directory.t5800-remote-helpers/server/.git/
Cloning into 'public'...
warning: You appear to have cloned an empty repository.
done.
[master (root-commit) 9a7aa46] one
 Author: A U Thor <author@example.com>
 1 file changed, 1 insertion(+)
 create mode 100644 file
Counting objects: 3, done.
Unpacking objects: 100% (3/3), done.
Writing objects: 100% (3/3), 219 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
To /devel/stefano/src/git/t/trash directory.t5800-remote-helpers/server
 * [new branch]      master -> master
ok 1 - setup repository

expecting success:
        git clone "testgit::${PWD}/server" localclone &&
        test_cmp public/file localclone/file

Cloning into 'localclone'...
ok 2 - cloning from local repo

expecting success:
        git clone "testgit::file://${PWD}/server" clone &&
        test_cmp public/file clone/file

Cloning into 'clone'...
ok 3 - cloning from remote repo

expecting success:
        (cd public &&
         echo content >>file &&
         git commit -a -m two &&
         git push)

[master 0eb255a] two
 Author: A U Thor <author@example.com>
 1 file changed, 1 insertion(+)
Counting objects: 5, done.
Unpacking objects: 100% (3/3), done.
Writing objects: 100% (3/3), 252 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
To /devel/stefano/src/git/t/trash directory.t5800-remote-helpers/server
   9a7aa46..0eb255a  master -> master
ok 4 - create new commit on remote

expecting success:
        (cd localclone && git pull) &&
        test_cmp public/file localclone/file

>From testgit::/devel/stefano/src/git/t/trash directory.t5800-remote-helpers/server
   9a7aa46..0eb255a  master     -> origin/master
Updating 9a7aa46..0eb255a
Fast-forward
 file |    1 +
 1 file changed, 1 insertion(+)
ok 5 - pulling from local repo

expecting success:
        (cd clone && git pull) &&
        test_cmp public/file clone/file

>From testgit::file:///devel/stefano/src/git/t/trash directory.t5800-remote-helpers/server
   9a7aa46..0eb255a  master     -> origin/master
Updating 9a7aa46..0eb255a
Fast-forward
 file |    1 +
 1 file changed, 1 insertion(+)
ok 6 - pulling from remote remote

expecting success:
        (cd localclone &&
        echo content >>file &&
        git commit -a -m three &&
        git push) &&
        compare_refs localclone HEAD server HEAD

[master 30d4cae] three
 Author: A U Thor <author@example.com>
 1 file changed, 1 insertion(+)

-*-*-

At this point, the test hangs, and I have to manually kill it with a SIGINT,
the result being:

-*-*-

Traceback (most recent call last):
  File "/devel/stefano/src/git/git-remote-testgit", line 265, in <module>
    sys.exit(main(sys.argv))
  File "/devel/stefano/src/git/git-remote-testgit", line 262, in main
    more = read_one_line(repo)
  File "/devel/stefano/src/git/git-remote-testgit", line 227, in read_one_line
    func(repo, cmdline)
  File "/devel/stefano/src/git/git-remote-testgit", line 175, in do_export
    changed = repo.importer.do_import(repo.gitdir)
  File "/home/stefano/src/git/t/../git_remote_helpers/build/lib/git_remote_helpers/git/importer.py", line 54, in do_import
    check_call(args)
  File "/home/stefano/src/git/t/../git_remote_helpers/build/lib/git_remote_helpers/util.py", line 169, in check_call
    retcode = call(*popenargs, **kwargs)
  File "/home/stefano/src/git/t/../git_remote_helpers/build/lib/git_remote_helpers/util.py", line 155, in call
    return subprocess.Popen(*popenargs, **kwargs).wait()
  File "/usr/lib/python2.7/subprocess.py", line 1291, in wait
    pid, sts = _eintr_retry_call(os.waitpid, self.pid, 0)
  File "/usr/lib/python2.7/subprocess.py", line 478, in _eintr_retry_call
    return func(*args)
KeyboardInterrupt
FATAL: Unexpected exit with code 0

-*-*-

If I run ps(1) in another terminal before interrupting the hung test, the
following command sticks out as a possible culprit:

git-fast-import --quiet --export-marks=/devel/stefano/src/git/t/trash \
directory.t5800-remote-helpers/localclone/.git/info/fast-import/\
c6c0871f9a7f12cd3f51aa290fbed7c49f539a8c/git.marks \
--import-marks=/devel/stefano/src/git/t/'trash directory.t5800-remote-helpers'/\
localclone/.git/info/fast-import/c6c0871f9a7f12cd3f51aa290fbed7c49f539a8c/\
git.marks

-*-*-

Other possibly relevant information:

  $ hg --version | head -1
  Mercurial Distributed SCM (version 1.8.3) $ python --version

  $ python --version
  Python 2.7.2+

  $ /bin/sh --version | head -1
  GNU bash, version 4.1.5(1)-release (i486-pc-linux-gnu)

  $ git describe
  v1.7.10-167-gf245c01