In that case the default value for tar.umask applies, which is 002. The
manpage needs an update.. Thanks for spotting this.
You can set it to 022 explicitly or to "user" to restrict permissions:
$ git config tar.umask 022 # -rw-r--r--
$ git config tar.umask user # your Unix umask applies
Originally file permissions were simply copied into the archive, but
this was inconvenient for users that needed more permission bits set,
e.g. to share an extracted archive with with others by default.
Also please note that tar applies your umask when extracting files
(exception: GNU tar doesn't do that by default if run as root), so the
permissions of extracted files may look different from the output of
"tar -t".
Ren