tests/test-dirstatedirs

test-extension: fix disabled extension tests for run-tests.py --local

One test that requires inserting a broken extension into hgext does this
by modifying PYTHONPATH. This doesn't work when run with --local because
the 'hg' script being used is in the same directory as the local hgext.

Instead of modifying PYTHONPATH, a secondary extension is enabled using
--config that inserts the dummy hgext at the beginning of sys.path,
before the script's path.

#!/bin/sh

# test dirstate._dirs refcounting
hg init t
cd t
mkdir -p a/b/c/d
touch a/b/c/d/x
touch a/b/c/d/y
touch a/b/c/d/z
hg ci -Am m
hg mv a z