tests/test-issue4074.t

tests: stabilize test-patch.t on Windows

$PYTHON needs to be quoted when invoking with cmd.exe, because the value expands
to c:/Python27/python.exe, which seems to be interpreted as 'c' being a command.
We can't just convert to '\', because there are a few places that run $PYTHON
directly in MSYS.  If unquoted there, it results in c:Python27python.exe being
run.  I wonder if we should bake the quotes into the environment variable to
avoid this.

It also wasn't happy with the quoting around exit1.py:

  c:/Python27/python.exe: can't open file ''$TESTTMP/d/exit1.py'': [Errno 22] Invalid argument

#require no-pure

A script to generate nasty diff worst-case scenarios:

  $ cat > s.py <<EOF
  > import random
  > for x in range(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)