feat(docker): add guided install and saved one-command updates

scripts/docker-config.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Read installation metadata as data, never execute it as a shell script.
+load_docker_config() {
+  local root="$1" key value mode="" public_url="" repository=""
+  [[ -f "$root/.docker-install" ]] || return 0
+  while IFS='=' read -r key value || [[ -n "$key" ]]; do
+    value="${value%$'\r'}"
+    case "$key" in
+      ''|'#'*) continue ;;
+      MODE) [[ "$value" = prebuilt || "$value" = source ]] || return 1; mode="$value" ;;
+      PUBLIC_URL) [[ "$value" =~ ^https?://[^[:space:]]+$ && "$value" != *'@'* && "$value" != *'?'* && "$value" != *'#'* ]] || return 1; public_url="$value" ;;
+      *) echo "Unknown installation setting: $key" >&2; return 1 ;;
+    esac
+  done < "$root/.docker-install"
+  [[ -n "$mode" && -n "$public_url" ]] || return 1
+  if [[ "$mode" = prebuilt && ! ${CMS_IMAGE_REPOSITORY+x} ]]; then
+    IFS= read -r repository < "$root/docker-image.txt"
+    repository="${repository%$'\r'}"
+    [[ "$repository" =~ ^[a-z0-9.-]+(:[0-9]+)?/[a-z0-9._/-]+$ ]] || return 1
+    export CMS_IMAGE_REPOSITORY="$repository"
+  fi
+  CMS_INSTALL_MODE="$mode"
+  export CMS_PUBLIC_URL="${CMS_PUBLIC_URL-$public_url}"
+}