metadata: add CLI script for printing image metadata

Add a utility script for printing image metadata from the command line.

Usage: `bin/lsmetadata 1.jpg 2.jpg`

bin/lsmetadata

@@ -0,0 +1,25 @@
+#!/usr/bin/env ruby
+
+# List metadata for given image and video files in JSON format.
+#
+# Usage:
+#
+#   bin/lsmetadata 1.jpg | jq        # list file
+#   bin/lsmetadata | jq              # list all files in current directory
+#   bin/lsmetadata images/ | jq      # list directory
+#   bin/lsmetadata images/**/* | jq  # list directory recursively
+#
+#   # Run from Docker without having to install Danbooru
+#   docker run -rm -it -v $PWD:/mnt ghcr.io/danbooru/danbooru bin/lsmetadata /mnt/images/**/* | jq
+
+APP_PATH = File.expand_path('../config/application', __dir__)
+require_relative "../config/environment"
+
+files = ARGV
+files = [Dir.pwd] if files.empty?
+files.map! { |file| File.directory?(file) ? Dir[file + "/*"] : file }.flatten!
+files.reject! { |file| File.directory?(file) }
+
+files.each do |filename|
+  puts MediaFile.open(filename).to_json
+end