clone: add tests for output directory

clone: add tests for output directory

When we run "git clone $url", clone guesses from the $url
what to name the local output directory. We don't have any
test coverage of this, so let's add some basic tests.

This reveals a few problems:

  - cloning "foo.git/" does not properly remove the ".git";
    this is a recent regression from 7e837c6 (clone:
    simplify string handling in guess_dir_name(), 2015-07-09)

  - likewise, cloning foo/.git does not seem to handle the
    bare case (we should end up in foo.git, but we try to
    use foo/.git on the local end), which also comes from
    7e837c6.

  - cloning the root is not very smart about URL parsing,
    and usernames and port numbers may end up in the
    directory name

All of these tests are marked as failures.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>