use Jekyll >= 3.6 to identify custom config files

Author: ashmaroli

.rubocop.yml

@@ -11,3 +11,5 @@ AllCops:
 
 Metrics/BlockLength:
   Enabled: false
+Style/FrozenStringLiteralComment:
+  Enabled: false

jekyll-admin.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "jekyll", "~> 3.3"
+  spec.add_dependency "jekyll", "~> 3.6"
   spec.add_dependency "sinatra", "~> 1.4"
   spec.add_dependency "sinatra-contrib", "~> 1.4"
   spec.add_dependency "addressable", "~> 2.4"

lib/jekyll-admin/server/configuration.rb

@@ -31,10 +31,6 @@ def parsed_configuration
         configuration.read_config_file(configuration_path)
       end
 
-      def custom_configs
-        Jekyll::Commands::Serve.custom_configs
-      end
-
       # Raw configuration content, as it sits on disk
       def raw_configuration
         File.read(
@@ -43,10 +39,12 @@ def raw_configuration
         )
       end
 
-      # Returns the path to the *first* config file discovered
+      # Returns the path to the *first* config file from the list passed to terminal
+      # switch +--config+ or the first of default config files to be discovered at the
+      # site's source directory.
       def configuration_path
-        if custom_configs
-          sanitized_path custom_configs.first
+        if site.config["config"]
+          sanitized_path site.config["config"].first
         else
           sanitized_path configuration.config_files(overrides).first
         end

lib/jekyll/commands/serve.rb

@@ -2,20 +2,6 @@ module Jekyll
   module Commands
     class Serve < Command
       class << self
-        def process(opts)
-          @overrides = opts["config"] if opts["config"]
-
-          opts = configuration_from_options(opts)
-          destination = opts["destination"]
-          setup(destination)
-
-          start_up_webrick(opts, destination)
-        end
-
-        def custom_configs
-          @custom_configs ||= @overrides
-        end
-
         def start_up_webrick(opts, destination)
           server = WEBrick::HTTPServer.new(webrick_opts(opts)).tap { |o| o.unmount("") }
           server.mount(opts["baseurl"], Servlet, destination, file_handler_opts)