Initially add gitconfig lexer [without tests]

lib/changit/lexer.rb

@@ -0,0 +1,53 @@
+module Changit
+  class Lexer
+    RULES = [
+      [/\[(.*?)\]/, SectionToken].freeze,
+      [/^[^(=|\[|\s)]*\s*\=\s*[^(=|\[|\])]*/, KeyValueToken].freeze
+    ].freeze
+
+    attr_reader :tokens, :token_hash
+
+    def initialize(expression)
+      @tokens = tokenize(expression)
+      @token_hash = to_hash
+    end
+
+    def to_s
+      @tokens.map(&:to_s).join
+    end
+
+    private
+
+    def tokenize(expression)
+      expression.gsub!(/\t/, '')
+
+      tokens = []
+      expression.each_line do |line|
+        RULES.each do |rule, token_type|
+          lexmeme = line.slice(rule)
+
+          if (lexmeme)
+            tokens << token_type.new(lexmeme)
+            break
+          end
+        end
+      end
+
+      tokens
+    end
+
+    def to_hash
+      token_hash = {}
+
+      @tokens.map do |token|
+        if token.class == SectionToken
+          token_hash[token] = []
+        else
+          token_hash[token_hash.to_a.last[0]].push(token)
+        end
+      end
+
+      token_hash
+    end
+  end
+end

lib/changit/lexer/key_value_token.rb

@@ -0,0 +1,22 @@
+module Changit
+  class Lexer
+    class KeyValueToken
+      include Comparable
+
+      attr_reader :lhs    # left-hand side
+      attr_accessor :rhs  # right-hand side
+
+      def initialize(key_value)
+        @lhs, @rhs = key_value.split('=').map(&:strip)
+      end
+
+      def to_s
+        "\t#{@lhs} = #{@rhs}\n"
+      end
+
+      def <=>(another)
+        self.lhs <=> another.lhs
+      end
+    end
+  end
+end

lib/changit/lexer/section_token.rb

@@ -0,0 +1,15 @@
+module Changit
+  class Lexer
+    class SectionToken
+      attr_reader :value
+
+      def initialize(section)
+        @section = section
+      end
+
+      def to_s
+        "#{@section}\n"
+      end
+    end
+  end
+end