Email subjects are prefixed with "[SCM] " by default, make this optionally
configurable through the hooks.emailprefix config option.
Suggested by martin f krafft through
http://bugs.debian.org/428418
Signed-off-by: Gerrit Pape <pape@smarden.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>