tests/test-clone-failure

actually port simplemerge to hg

- use bdiff instead of patiencediff;  this is a larger change, since
  bdiff works on 2 multi-line strings, while patiencediff works on 2
  lists;

- rename the main class from Merge3 to Merge3Text and add a Merge3
  class that derives from Merge3Text.  This new Merge3 class has
  the same interface from the original class, so that the tests
  still work;

  - Merge3 uses util.binary to detect binary data and raises
    util.Abort instead of a specific exception;

- don't use the @decorator syntax, to keep python2.3 compatibility;

- the test uses unittest, which likes to print how long it took to
  run.  This obviously doesn't play too well with hg's test suite,
  so we override time.time to fool unittest;

- one test has a different (but still valid) output because of the
  different diff algorithm used;

- the TestCase class used by bzr has some extras to help debugging.
  test-merge3.py used 2 of them:

  - log method to log some data

  - assertEqualDiff method to ease viewing diffs of diffs

  We add a dummy log method and use regular assertEquals instead of
  assertEqualDiff.

- make simplemerge executable and add "#!/usr/bin/env python" header

#!/bin/sh

# No local source
hg clone a b
echo $?

# No remote source
hg clone http://127.0.0.1:3121/a b
echo $?
rm -rf b # work around bug with http clone

# Inaccessible source
mkdir a
chmod 000 a
hg clone a b
echo $?

# Inaccessible destination
mkdir b
cd b
hg init
hg clone . ../a
echo $?
cd ..
chmod 700 a
rm -r a b

# Source of wrong type
mkfifo a
hg clone a b
echo $?
rm a

# Default destination, same directory
mkdir q
cd q
hg init
cd ..
hg clone q

true