put spec assembly into independent script

as in it doesn't require bundling or a database
conncetion as opposed to a rake task

lib/tasks/api.rake

@@ -45,24 +45,4 @@ namespace :api do
       puts "#{method} #{path}"
     end
   end
-
-  desc 'Saves the complete API spec (OAS 3.0) as a single json (default) or YAML file.'
-  task save_spec: [:environment] do
-    if ARGV.size != 2
-      $stderr.puts "usage: rake api:save_spec <file-name>"
-      exit 1
-    end
-
-    file_name = ARGV.last
-    format = (file_name =~ /\.ya?ml\Z/i) ? :yml : :json
-    spec = API::OpenAPI.spec
-    
-    File.open(file_name, "w") do |f|
-      if format == :yml
-        f.puts spec.to_yaml
-      else
-        f.puts spec.to_json
-      end
-    end
-  end
 end

script/api/spec

@@ -0,0 +1,28 @@
+#!/usr/bin/env ruby
+
+if ARGV.join(" ") =~ /((\-h)|(\-\-help))/
+  puts "Prints the self-contained OpenAPI 3.0 specification of OpenProject's APIv3"
+  puts
+  puts "usage: ./scripts/api/spec [--format JSON|yaml]"
+  return
+end
+
+require 'pathname'
+require 'yaml'
+require 'json'
+
+require './lib/api/open_api.rb'
+
+path = Pathname(__dir__).join("../../docs/api/apiv3/openapi-spec.yml")
+spec = API::OpenAPI.assemble_spec path
+format = ARGV.join(" ") =~ /((\-\-format)|(\-f))((=)|(\s+))ya?ml/ ? :yaml : :json
+
+begin
+  if format == :yaml
+    puts spec.to_yaml
+  else
+    puts spec.to_json
+  end
+rescue Errno::EPIPE
+  # `head` for instance closes the pipe when it has what it needs
+end