tests/test-issue4074.t

phabricator: add a config to use curl for communication

Not sure why, but I got `phabsend` hang on work network pretty frequently.
The traceback indicates it hangs at `_sslobj.do_handshake()`:

  File "mercurial/sslutil.py", line 404, in wrapsocket
    sslsocket = sslcontext.wrap_socket(sock, server_hostname=serverhostname)
  File "/usr/lib/python2.7/ssl.py", line 363, in wrap_socket
    _context=self)
  File "/usr/lib/python2.7/ssl.py", line 611, in __init__
    self.do_handshake()
  File "/usr/lib/python2.7/ssl.py", line 840, in do_handshake
    self._sslobj.do_handshake()

I had tried adding `timeout` in various places but they seem not effective.
It seems easier to just allow shelling out to `curl` with retry and timeout
flags.

This could also be helpful for people with an older Python installed without
modern security (SNI).

Differential Revision: https://phab.mercurial-scm.org/D605

#require no-pure

A script to generate nasty diff worst-case scenarios:

  $ cat > s.py <<EOF
  > import random
  > for x in xrange(100000):
  >     print
  >     if random.randint(0, 100) >= 50:
  >         x += 1
  >     print(hex(x))
  > EOF

  $ hg init a
  $ cd a

Check in a big file:

  $ $PYTHON ../s.py > a
  $ hg ci -qAm0

Modify it:

  $ $PYTHON ../s.py > a

Time a check-in, should never take more than 10 seconds user time:

  $ hg ci --time -m1
  time: real .* secs .user [0-9][.].* sys .* (re)