add --time-style option in long style format

lib/colorls/core.rb

@@ -28,7 +28,7 @@ module ColorLS
     def initialize(all: false, sort: false, show: false,
       mode: nil, git_status: false, almost_all: false, colors: [], group: nil,
       reverse: false, hyperlink: false, tree_depth: nil, show_group: true, show_user: true,
-      indicator_style: 'slash')
+      indicator_style: 'slash', time_style: '')
       @count = {folders: 0, recognized_files: 0, unrecognized_files: 0}
       @all          = all
       @almost_all   = almost_all
@@ -42,6 +42,7 @@ module ColorLS
       @tree         = {mode: mode == :tree, depth: tree_depth}
       @horizontal   = mode == :horizontal
       @git_status   = init_git_status(git_status)
+      @time_style   = time_style
       @indicator_style = indicator_style
 
       init_colors colors
@@ -249,7 +250,7 @@ module ColorLS
     end
 
     def mtime_info(file_mtime)
-      mtime = file_mtime.asctime
+      mtime = @time_style.empty? ? file_mtime.asctime : file_mtime.strftime(@time_style)
       now = Time.now
       return mtime.colorize(@colors[:hour_old]) if now - file_mtime < 60 * 60
       return mtime.colorize(@colors[:day_old])  if now - file_mtime < 24 * 60 * 60

lib/colorls/flags.rb

@@ -107,7 +107,8 @@ module ColorLS
         tree_depth: 3,
         show_group: true,
         show_user: true,
-        indicator_style: 'slash'
+        indicator_style: 'slash',
+        time_style: ''
       }
     end
 
@@ -183,6 +184,9 @@ module ColorLS
         @opts[:show_user] = false
       end
       options.on('-G', '--no-group', 'show no group information in a long listing') { @opts[:show_group] = false }
+      options.on('--time-style=FORMAT', String, 'use time display format') do |time_style|
+        @opts[:time_style] = time_style
+      end
     end
 
     def add_general_options(options)

spec/color_ls/flags_spec.rb

@@ -550,4 +550,12 @@ RSpec.describe ColorLS::Flags do
 
     it { expect { subject }.to output(/.+second-level \n.+symlinks \n/).to_stdout }
   end
+
+  context 'with --time-style option' do
+    let(:args) { ['-l', '--time-style=%y-%m-%d %k:%M', "#{FIXTURES}/a.txt"] }
+
+    mtime = File.mtime("#{FIXTURES}/a.txt")
+
+    it { expect { subject }.to output(/#{mtime.strftime("%y-%m-%d %k:%M")}/).to_stdout }
+  end
 end