clone: --naked option.

clone: --naked option.

The new option --naked is to help creating a naked repository
for public consumption.

	$ git clone -l -s --naked \
	  /pub/scm/.../torvalds/linux-2.6.git subproj-2.6.git

is equivalent to this sequence:

	$ git clone -l -s -n /pub/scm/.../torvalds/linux-2.6.git temp
	$ mv temp/.git subproj-2.6.git
	$ rmdir temp

Signed-off-by: Junio C Hamano <junkio@cox.net>