Drop ed & reverse_ed formats

These formats are super old and very unlikely used.
Their implementation was broken for a while and no-one reported it.

The GNU doc say that ed format is "almost obsolete". [1]
The reverse_ed (aka forward-ed) is described as "not very useful". [2]

[1]: https://www.gnu.org/software/diffutils/manual/html_node/ed-Scripts.html
[2]: https://www.gnu.org/software/diffutils/manual/html_node/Forward-ed.html

lib/diff/lcs/hunk.rb

@@ -7,9 +7,8 @@
 # block.) Used in the diff program (bin/ldiff).
 class Diff::LCS::Hunk
   OLD_DIFF_OP_ACTION = {"+" => "a", "-" => "d", "!" => "c"}.freeze # :nodoc:
-  ED_DIFF_OP_ACTION = {"+" => "a", "-" => "d", "!" => "c"}.freeze # :nodoc:
 
-  private_constant :OLD_DIFF_OP_ACTION, :ED_DIFF_OP_ACTION if respond_to?(:private_constant)
+  private_constant :OLD_DIFF_OP_ACTION, if respond_to?(:private_constant)
 
   # Create a hunk using references to both the old and new data, as well as the
   # piece of data.
@@ -120,10 +119,6 @@ def diff(format, last = false)
       unified_diff(last)
     when :context
       context_diff(last)
-    when :ed
-      self
-    when :reverse_ed, :ed_finish
-      ed_diff(format, last)
     else
       fail "Unknown diff format #{format}."
     end
@@ -273,26 +268,6 @@ def context_diff(last = false)
   end
   private :context_diff
 
-  def ed_diff(format, _last = false)
-    warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1
-
-    s =
-      if format == :reverse_ed
-        encode("#{ED_DIFF_OP_ACTION[@blocks[0].op]}#{context_range(:old, ",")}\n")
-      else
-        encode("#{context_range(:old, " ")}#{ED_DIFF_OP_ACTION[@blocks[0].op]}\n")
-      end
-
-    unless @blocks[0].insert.empty?
-      @data_new[@start_new..@end_new].each do |e|
-        s << e.chomp + encode("\n")
-      end
-      s << encode(".\n")
-    end
-    s
-  end
-  private :ed_diff
-
   # Generate a range of item numbers to print. Only print 1 number if the
   # range has only one item in it. Otherwise, it's 'start,end'
   def context_range(mode, op, last = false)

lib/diff/lcs/ldiff.rb

@@ -44,12 +44,6 @@ def run(args, _input = $stdin, output = $stdout, error = $stderr) # :nodoc:
         @format = :unified
         @lines = ctx || 3
       end
-      o.on("-e", "Creates an 'ed' script to change", "oldfile to newfile.") do |_ctx|
-        @format = :ed
-      end
-      o.on("-f", "Creates an 'ed' script to change", "oldfile to newfile in reverse order.") do |_ctx|
-        @format = :reverse_ed
-      end
       o.on(
         "-a", "--text",
         "Treat the files as text and compare them", "line-by-line, even if they do not seem", "to be text."
@@ -140,11 +134,6 @@ def run(args, _input = $stdin, output = $stdout, error = $stderr) # :nodoc:
     # Otherwise, print out the old one.
     oldhunk = hunk = nil
 
-    if @format == :ed
-      real_output = output
-      output = []
-    end
-
     diffs.each do |piece|
       begin # rubocop:disable Style/RedundantBegin
         hunk = Diff::LCS::Hunk.new(data_old, data_new, piece, @lines, file_length_difference)
@@ -165,8 +154,6 @@ def run(args, _input = $stdin, output = $stdout, error = $stderr) # :nodoc:
 
     output << last
 
-    output.reverse_each { |e| real_output << e.diff(:ed_finish) } if @format == :ed
-
     1
   end
 end

spec/hunk_spec.rb

@@ -56,17 +56,6 @@
       expect(hunk.diff(:old)).to eq(expected)
     end
 
-    it "produces a reverse ed diff from the two pieces" do
-      expected = <<-EXPECTED.gsub(/^ +/, "").encode("UTF-16LE").chomp
-        c1
-        Tu a un carte avec {count} items
-        .
-
-      EXPECTED
-
-      expect(hunk.diff(:reverse_ed)).to eq(expected)
-    end
-
     context "with empty first data set" do
       let(:old_data) { [] }
 

spec/ldiff_spec.rb

@@ -10,7 +10,7 @@
     {:name => "output.diff", :left => "aX", :right => "bXaX"},
     {:name => "output.diff.chef", :left => "old-chef", :right => "new-chef"},
     {:name => "output.diff.chef2", :left => "old-chef2", :right => "new-chef2"}
-  ].product([nil, "-e", "-f", "-c", "-u"]).map { |(fixture, flag)|
+  ].product([nil, "-c", "-u"]).map { |(fixture, flag)|
     fixture = fixture.dup
     fixture[:flag] = flag
     fixture