t5580: test cloning without file://, test fetching via UNC paths

t5580: test cloning without file://, test fetching via UNC paths

On Windows, it is quite common to work with network drives. The format
of the paths to network drives (or "network shares", or UNC paths) is:

	\\<server>\<share>\...

We already have a couple regression tests revolving around those types
of paths, but we missed cloning and fetching from UNC paths without
leading `file://` (and with backslashes instead of forward slashes).
This lil' patch closes that gap.

It gets a bit silly to add the commands to the name of the test script,
so let's just rename it while we're testing more UNC stuff.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>