SCRIPTS: create-release: enforce GIT_COMMITTER_{NAME|EMAIL} validity

If it's not set, fall back to git config --get.
diff --git a/scripts/create-release b/scripts/create-release
index 488c0ce..afd6e56 100755
--- a/scripts/create-release
+++ b/scripts/create-release
@@ -48,6 +48,16 @@
 	git tag -u "$GIT_GPG_KEY" -s -m "HAProxy $NEW" v$NEW && echo "Tagged as v$NEW"
 }
 
+if [ -z "$GIT_COMMITTER_NAME" ]; then
+	GIT_COMMITTER_NAME=$(git config --get user.name)
+	[ -n "$GIT_COMMITTER_NAME" ] || die "GIT_COMMITTER_NAME not set"
+fi
+
+if [ -z "$GIT_COMMITTER_EMAIL" ]; then
+	GIT_COMMITTER_EMAIL=$(git config --get user.email)
+	[ -n "$GIT_COMMITTER_EMAIL" ] || die "GIT_COMMITTER_EMAIL not set"
+fi
+
 while [ -n "$1" -a -z "${1##-*}" ]; do
 	case "$1" in
 		-y)        SAYYES=1       ; shift   ;;