gitweb: do not choke on recursive symlink

gitweb: do not choke on recursive symlink

If somebody used to advertise his repository that physically
resides at /pub/lic.git/ as:

	git://git.example.com/pub/lic.git/

but now wants to use --base-path to allow:

	git://git.example.com/lic.git/

she can start git-daemon with --base-path option, like this:

	git-daemon --base-path=/pub --export-all

During the transition, however, she would also want to allow
older URL as well.  One natural way to achieve that is to create
a symlink:

	ln -s /pub /pub/pub

so that a request to git://git.example.com/pub/lic.git/ is first
translated by --base-path to a request to /pub/pub/lic.git/
which goes to /pub/lic.git, thanks to the symlink.

So far so good.

However, gitweb chokes if there is such a symlink (File::Find
barfs with "/pub/pub is a recursive symbolic link").  Make the
code ignore such a symlink.

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