feat: add expandable diff excerpts with configurable context

src/ruby_config.rb

@@ -16,6 +16,8 @@ module Vamp
       @file_picker_view = "tree"
       @file_explorer_view = "tree"
       @clipboard_mode = "system"
+      @diff_context_lines = 10
+      @diff_expand_lines = 15
     end
 
     # @param path [String] relative to the configuration file
@@ -60,6 +62,18 @@ module Vamp
       @clipboard_mode = nonempty_string!(mode, "clipboard mode")
     end
 
+    # @param lines [Integer] nonnegative context lines around each diff change
+    # @return [Integer]
+    def diff_context_lines=(lines)
+      @diff_context_lines = diff_line_count!(lines, "diff_context_lines", 0)
+    end
+
+    # @param lines [Integer] positive lines revealed per diff expansion
+    # @return [Integer]
+    def diff_expand_lines=(lines)
+      @diff_expand_lines = diff_line_count!(lines, "diff_expand_lines", 1)
+    end
+
     # @return [Module<Vamp::Core>] frozen namespace with catalog-generated Action methods
     def core
       Core
@@ -90,11 +104,26 @@ module Vamp
     def response
       { "version" => 1, "type" => "config", "plugins" => @plugins, "lsp" => lsp_options, "bindings" => @bindings,
         "leader" => @leader, "file_explorer_side" => @file_explorer_side, "file_picker_view" => @file_picker_view,
-        "file_explorer_view" => @file_explorer_view, "clipboard_mode" => @clipboard_mode }
+        "file_explorer_view" => @file_explorer_view, "clipboard_mode" => @clipboard_mode,
+        "diff_context_lines" => @diff_context_lines, "diff_expand_lines" => @diff_expand_lines }
     end
 
     private
 
+    # @param value [Integer]
+    # @param label [String]
+    # @param minimum [Integer]
+    # @return [Integer]
+    def diff_line_count!(value, label, minimum)
+      raise TypeError, "#{label} must be an Integer" unless value.is_a?(Integer)
+      maximum = (1 << 64) - 1
+      unless value.between?(minimum, maximum)
+        raise ArgumentError, "#{label} must be between #{minimum} and #{maximum}"
+      end
+
+      value
+    end
+
     # @param value [String]
     # @param label [String]
     # @return [String]