Allow config file to specify Signed-off-by identity in format-patch.

Allow config file to specify Signed-off-by identity in format-patch.

Unlike git-commit, git-format-patch was not picking up and using the
user.email config variable for the email part of the committer info.
I was forced to use the GIT_COMMITTER_EMAIL environment variable to
override the default <user@localhost.localdomain>. The fix was to
simply move the call to setup_ident() to come before the git_config()
call.

Signed-off-by: Ramsay Allan Jones <ramsay@ramsay1.demon.co.uk>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>