safe.directory: setting safe.directory="." allows the "current" directory

safe.directory: setting safe.directory="." allows the "current" directory

When "git daemon" enters a repository, it chdir's to the requested
repository and then uses "." (the curent directory) to consult the
"is this repository considered safe?" when it is not owned by the
same owner as the process.

Make sure this access will be allowed by setting safe.directory to
".", as that was once advertised on the list as a valid workaround
to the overly tight safe.directory settings introduced by 2.45.1
(cf. <834862fd-b579-438a-b9b3-5246bf27ce8a@gmail.com>).

Also add simlar test to show what happens in the same setting if the
safe.directory is set to "*" instead of "."; in short, "." is a bit
tighter (as it is custom designed for git-daemon situation) than
"anything goes" settings given by "*".

Signed-off-by: Junio C Hamano <gitster@pobox.com>