contrib/hooks/post-receive-email: make subject prefix configurable

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>

contrib/hooks/post-receive-email

@@ -35,10 +35,12 @@
 # hooks.envelopesender
 #   If set then the -f option is passed to sendmail to allow the envelope
 #   sender address to be set
+# hooks.emailprefix
+#   All emails have their subjects prefixed with this prefix, or "[SCM]"
+#   if emailprefix is unset, to aid filtering
 #
 # Notes
 # -----
-# All emails have their subjects prefixed with "[SCM]" to aid filtering.
 # All emails include the headers "X-Git-Refname", "X-Git-Oldrev",
 # "X-Git-Newrev", and "X-Git-Reftype" to enable fine tuned filtering and
 # give information for debugging.
@@ -188,7 +190,7 @@ generate_email_header()
 	# Generate header
 	cat <<-EOF
 	To: $recipients
-	Subject: ${EMAILPREFIX}$projectdesc $refname_type, $short_refname, ${change_type}d. $describe
+	Subject: ${emailprefix}$projectdesc $refname_type, $short_refname, ${change_type}d. $describe
 	X-Git-Refname: $refname
 	X-Git-Reftype: $refname_type
 	X-Git-Oldrev: $oldrev
@@ -604,7 +606,6 @@ send_mail()
 # ---------------------------- main()
 
 # --- Constants
-EMAILPREFIX="[SCM] "
 LOGBEGIN="- Log -----------------------------------------------------------------"
 LOGEND="-----------------------------------------------------------------------"
 
@@ -628,6 +629,7 @@ fi
 recipients=$(git repo-config hooks.mailinglist)
 announcerecipients=$(git repo-config hooks.announcelist)
 envelopesender=$(git-repo-config hooks.envelopesender)
+emailprefix=$(git-repo-config hooks.emailprefix || echo '[SCM] ')
 
 # --- Main loop
 # Allow dual mode: run from the command line just like the update hook, or