Old Bash (3.0) which is distributed with RHEL 4.X and other ancient
platforms that are still in wide use, do not have a printf that
supports -v. Neither does Zsh (which is already handled in the code).
As suggested by Junio, let's test whether printf supports the -v
option and store the result. Then later, we can use it to
determine whether 'printf -v' can be used, or whether printf
must be called in a subshell.
Signed-off-by: Brandon Casey <drafnel@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>