Restore umasks influence on the permissions of work tree created by clone

Restore umasks influence on the permissions of work tree created by clone

The original version of the git-clone just used mkdir(1) to create
the working directories.  The version rewritten in C creates all
directories inside the working tree by using the mode argument of
0777 when calling mkdir(2) to let the umask take effect.

But the top-level directory of the working tree is created by
passing the mode argument of 0755 to mkdir(2), which results in an
overly tight restriction if the user wants to make directories group
writable with a looser umask like 002.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>