scripts/bw-compatibility-test: add backwards compat test

In this commit, a new backwards compatibility test is added. See the
added README.md file in this commit for all the info.

scripts/bw-compatibility-test/compose.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+
+# DIR is set to the directory of this script.
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# The way we call docker-compose depends on the installation.
+if which docker-compose > /dev/null; then
+  COMPOSE_CMD="docker-compose"
+else
+  COMPOSE_CMD="docker compose"
+fi
+
+# Common arguments that we want to pass to docker-compose.
+# By default, this only includes the main docker-compose file
+# and not the override file. Use the `compose_upgrade` method
+# to load both docker compose files.
+COMPOSE_ARGS="-f $DIR/docker-compose.yaml -p regtest"
+COMPOSE="$COMPOSE_CMD $COMPOSE_ARGS"
+
+# compose_upgrade sets COMPOSE_ARGS and COMPOSE such that
+# both the main docker-compose file and the override file
+# are loaded.
+function compose_upgrade() {
+  export COMPOSE_ARGS="-p regtest"
+  export COMPOSE="$COMPOSE_CMD $COMPOSE_ARGS"
+}
+
+# compose_up starts the docker-compose cluster.
+function compose_up() {
+  echo "🐳 Starting the cluster"
+  $COMPOSE up -d --quiet-pull
+}
+
+# compose_down tears down the docker-compose cluster
+# and removes all volumes and orphans.
+function compose_down() {
+  echo "🐳 Tearing down the cluster"
+  $COMPOSE down --volumes --remove-orphans
+}
+
+# compose_stop stops a specific service in the cluster.
+function compose_stop() {
+  local service="$1"
+  echo "🐳 Stopping $service"
+  $COMPOSE stop "$service"
+}
+
+# compose_start starts a specific service in the cluster.
+function compose_start() {
+  local service="$1"
+  echo "🐳 Starting $service"
+  $COMPOSE up -d $service
+}
+
+# compose_rebuild forces the rebuild of the image for a
+# specific service in the cluster.
+function compose_rebuild() {
+  local service="$1"
+  echo "🐳 Rebuilding $service"
+  $COMPOSE build --no-cache $service
+}