feat: follow forward working-checkout changes in diffs

src/ruby_config.rb

@@ -144,6 +144,7 @@ module Vamp
       @diff_expand_lines = 15
       @diff_view_mode = "split"
       @diff_split_orientation = "vertical"
+      @diff_follow_working_copy = true
     end
 
     # @param path [String] relative to the configuration file
@@ -234,6 +235,14 @@ module Vamp
       @diff_split_orientation = orientation
     end
 
+    # @param enabled [Boolean]
+    # @return [Boolean]
+    def diff_follow_working_copy=(enabled)
+      raise TypeError, "diff_follow_working_copy must be true or false" unless [true, false].include?(enabled)
+
+      @diff_follow_working_copy = enabled
+    end
+
     # @return [Module<Vamp::Core>] frozen namespace with catalog-generated Action methods
     def core
       Core
@@ -269,7 +278,8 @@ module Vamp
         "top_bar" => @bar.top, "bottom_bar" => @bar.bottom, "labels" => @labels,
         "popup" => { "command" => @popup.command, "search" => @popup.search },
         "diff_context_lines" => @diff_context_lines, "diff_expand_lines" => @diff_expand_lines,
-        "diff_view_mode" => @diff_view_mode, "diff_split_orientation" => @diff_split_orientation }
+        "diff_view_mode" => @diff_view_mode, "diff_split_orientation" => @diff_split_orientation,
+        "diff_follow_working_copy" => @diff_follow_working_copy }
     end
 
     private