filter-branch: use printf instead of echo -e

filter-branch: use printf instead of echo -e

In order to echo a tab character, it's better to use printf instead of
"echo -e", because it's more portable (for instance, "echo -e" doesn't work
as expected on a Mac).

This solves the "fatal: Not a valid object name" error in git-filter-branch
when using the --state-branch option.

Furthermore, let's switch from "/bin/echo" to just "echo", so that the
built-in echo command is used where available.

Signed-off-by: Michele Locati <michele@locati.it>
Signed-off-by: Junio C Hamano <gitster@pobox.com>