feat: add configurable three-pane conflict views

src/ruby_config.rb

@@ -157,6 +157,7 @@ module Vamp
       @diff_view_mode = "split"
       @diff_split_orientation = "vertical"
       @diff_follow_working_copy = true
+      @resolve_history_layout = "columns"
     end
 
     # @param path [String] relative to the configuration file
@@ -326,6 +327,16 @@ module Vamp
       @diff_follow_working_copy = enabled
     end
 
+    # @param layout [String] "columns" or "base_below"
+    # @return [String]
+    def resolve_history_layout=(layout)
+      layout = nonempty_string!(layout, "resolve history layout")
+      unless %w[columns base_below].include?(layout)
+        raise ArgumentError, "resolve history layout must be columns or base_below"
+      end
+      @resolve_history_layout = layout
+    end
+
     # @return [Module<Vamp::Core>] frozen namespace with catalog-generated Action methods
     def core
       Core
@@ -370,7 +381,8 @@ module Vamp
         "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_follow_working_copy" => @diff_follow_working_copy }
+        "diff_follow_working_copy" => @diff_follow_working_copy,
+        "resolve_history_layout" => @resolve_history_layout }
     end
 
     private