Implemented changes related to diff-lcs for knife diff

1 files changed, 40 insertions, 1 deletions

diff --git a/lib/chef/chef_fs/command_line.rb b/lib/chef/chef_fs/command_line.rb
index dd5e62b755..f41ca38824 100644
--- a/lib/chef/chef_fs/command_line.rb
+++ b/lib/chef/chef_fs/command_line.rb
@@ -19,6 +19,8 @@
 require 'chef/chef_fs/file_system'
 require 'chef/chef_fs/file_system/operation_failed_error'
 require 'chef/chef_fs/file_system/operation_not_allowed_error'
+require 'diff/lcs'
+require 'diff/lcs/hunk'
 
 class Chef
   module ChefFS
@@ -235,6 +237,43 @@ class Chef
         return [ [ :error, old_entry, new_entry, nil, nil, e ] ]
       end
 
+      # @todo: abstract out udiff. Same code for udiff is exist in 'chef/util/diff'
+      # produces a unified-output-format diff with 3 lines of context
+      def self.udiff(old_file, new_file)
+        diff_str = ""
+        file_length_difference = 0
+
+        old_data = IO.readlines(old_file).map { |e| e.chomp }
+        new_data = IO.readlines(new_file).map { |e| e.chomp }
+        diff_data = ::Diff::LCS.diff(old_data, new_data)
+
+        return diff_str if old_data.empty? && new_data.empty?
+        return "No differences encountered\n" if diff_data.empty?
+
+        # write diff header (standard unified format)
+        ft = File.stat(old_file).mtime.localtime.strftime('%Y-%m-%d %H:%M:%S.%N %z')
+        diff_str << "--- #{old_file}\t#{ft}\n"
+        ft = File.stat(new_file).mtime.localtime.strftime('%Y-%m-%d %H:%M:%S.%N %z')
+        diff_str << "+++ #{new_file}\t#{ft}\n"
+
+        # loop over diff hunks. if a hunk overlaps with the last hunk,
+        # join them. otherwise, print out the old one.
+        old_hunk = hunk = nil
+        diff_data.each do |piece|
+          begin
+            hunk = ::Diff::LCS::Hunk.new(old_data, new_data, piece, 3, file_length_difference)
+            file_length_difference = hunk.file_length_difference
+            next unless old_hunk
+            next if hunk.merge(old_hunk)
+            diff_str << old_hunk.diff(:unified) << "\n"
+          ensure
+            old_hunk = hunk
+          end
+        end
+        diff_str << old_hunk.diff(:unified) << "\n"
+        return diff_str
+      end
+
       private
 
       def self.sort_keys(json_object)
@@ -268,7 +307,7 @@ class Chef
             old_tempfile.write(old_value)
             old_tempfile.close
 
-            result = `diff -u #{old_tempfile.path} #{new_tempfile.path}`
+            result = udiff(old_tempfile.path, new_tempfile.path)
             result = result.gsub(/^--- #{old_tempfile.path}/, "--- #{old_path}")
             result = result.gsub(/^\+\+\+ #{new_tempfile.path}/, "+++ #{new_path}")
             result