Add support for reverse sorting

Re-assign the `-r` short option from `--report` to `--reverse` and mention this
change in the post install message.

colorls.gemspec

@@ -16,6 +16,7 @@ ColorLS::POST_INSTALL_MESSAGE = %(
     Tab completion enabled for flags
 
     -t flag : Previously short for --tree, has been re-allocated to sort results by time
+    -r flag : Previously short for --report, has been re-allocated to reverse sort results
 
   *******************************************************************
 ).freeze

lib/colorls/core.rb

@@ -1,13 +1,15 @@
 module ColorLS
   class Core
     def initialize(input=nil, all: false, report: false, sort: false, show: false,
-      one_per_line: false, git_status: false,long: false, almost_all: false, tree: false, colors: [], group: nil)
+      one_per_line: false, git_status: false,long: false, almost_all: false, tree: false, colors: [], group: nil,
+      reverse: false)
       @input        = init_input_path(input)
       @count        = {folders: 0, recognized_files: 0, unrecognized_files: 0}
       @all          = all
       @almost_all   = almost_all
       @report       = report
       @sort         = sort
+      @reverse      = reverse
       @group        = group
       @show         = show
       @one_per_line = one_per_line
@@ -115,6 +117,7 @@ module ColorLS
       else
         @contents.sort! { |a, b| a.casecmp(b) }
       end
+      @contents.reverse! if @reverse
     end
 
     def group_contents(path)

lib/colorls/flags.rb

@@ -11,6 +11,7 @@ module ColorLS
       @opts = {
         show: false,
         sort: true,
+        reverse: false,
         group: nil,
         all: false,
         almost_all: false,
@@ -62,6 +63,8 @@ module ColorLS
                        when 'time' then :time
                        end
       end
+
+      options.on('-r', '--reverse', 'reverse order while sorting') { @opts[:reverse] = true }
     end
 
     def add_common_options(options)
@@ -69,7 +72,7 @@ module ColorLS
       options.on('-A', '--almost-all', 'do not list . and ..')            { @opts[:almost_all] = true }
       options.on('-l', '--long', 'use a long listing format')             { @mode = :long }
       options.on('--tree', 'shows tree view of the directory')            { @mode = :tree }
-      options.on('-r', '--report', 'show brief report')                   { @opts[:report] = true }
+      options.on('--report', 'show brief report')                         { @opts[:report] = true }
       options.on('-1', 'list one file per line')                          { @mode = :one_per_line }
       options.on('-d', '--dirs', 'show only directories')                 { @opts[:show] = :dirs }
       options.on('-f', '--files', 'show only files')                      { @opts[:show] = :files }

spec/flags_spec.rb

@@ -26,6 +26,12 @@ RSpec.describe ColorLS::Flags do
     it { is_expected.to_not match(/├──/) } # does not display file hierarchy
   end
 
+  context 'with --reverse flag' do
+    let(:args) { ['--reverse', FIXTURES] }
+
+    it { is_expected.to match(/z-file.+symlinks.+a-file/) } # displays dirs & files in reverse alphabetical order
+  end
+
   context 'with --long flag & file path' do
     let(:args) { ['--long', "#{FIXTURES}/.hidden-file"] }