hack/pin-release-image: Add a helper for pinning release images

hack/pin-release-image.sh

@@ -0,0 +1,31 @@
+#!/bin/sh
+#
+# Usage:
+#
+#   pin-release-image PATH PULLSPEC
+#
+# edits the openshift-install executable at PATH in place to replace
+# the default release pullspec with the user-provided PULLSPEC.
+
+set -e
+
+OPENSHIFT_INSTALL="${1}"
+RELEASE_IMAGE="${2}"
+PLACEHOLDER_A='_RELEASE_IMAGE_LOCATION_'
+PLACEHOLDER_B='XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
+
+MAX_LENGTH="$((1 + ${#PLACEHOLDER_A} + 1 + ${#PLACEHOLDER_B}))"
+PADDING_COUNT="$((MAX_LENGTH - ${#RELEASE_IMAGE}))"
+if test 0 -gt "${PADDING_COUNT}"
+then
+	printf 'release image is %d characters long, but the limit is %d\n' "${#RELEASE_IMAGE}" "${MAX_LENGTH}" >&2
+	exit 1
+fi
+
+PADDING=''
+while test "${PADDING_COUNT}" -gt "${#PADDING}"
+do
+	PADDING="${PADDING}X"
+done
+
+exec sed -i "s|\\x0${PLACEHOLDER_A}\\x0${PLACEHOLDER_B}\\x0|${RELEASE_IMAGE}\\x0${PADDING}|" "${OPENSHIFT_INSTALL}"