tests/test-issue4074.t

testlib: move the prune alias into a shell script for Windows

Cramming all of this directly into an alias doesn't play nicely on Windows.
Various test-exchange-obsmarkers-case-XX.t were failing with:

    abort: cannot select revision when creating marker

It turned out that inside debugcommands.debugobsolete(), the following differed
from Linux (where they were empty, at least in the case I debugged):

    'rev': ['.`;'],
    'template': "'{node}\\n'"

#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)