Expose build refs in .env, add build script, default GNUnet v0.26.1

scripts/build-image.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "${ROOT_DIR}"
+
+if [[ -f ".env" ]]; then
+  set -a
+  # shellcheck disable=SC1091
+  source ".env"
+  set +a
+fi
+
+IMAGE_TAG="${IMAGE_TAG:-taler-stack:build}"
+
+docker build \
+  --build-arg GNUNET_REF="${GNUNET_REF:-v0.26.1}" \
+  --build-arg GNUNET_TARBALL_URL="${GNUNET_TARBALL_URL:-}" \
+  --build-arg EXCHANGE_REF="${EXCHANGE_REF:-master}" \
+  --build-arg MERCHANT_REF="${MERCHANT_REF:-master}" \
+  --build-arg LIBEUFIN_REF="${LIBEUFIN_REF:-master}" \
+  -t "${IMAGE_TAG}" .
+
+echo "Built image ${IMAGE_TAG}"