Handle else if statement in makefile (rouge-ruby#2063)

Author: tancnle

lib/rouge/lexers/make.rb

@@ -40,6 +40,10 @@ def initialize(opts={})
           groups Keyword, Text, Name::Variable
         end
 
+        rule %r/(else\b)([\t ]+)((?:ifn?def|ifn?eq)\b)([\t ]+)([^#\n]+)/ do
+          groups Keyword, Text, Keyword, Text, Name::Variable
+        end
+
         rule %r/(?:else|endif|endef|endfor)[\t ]*(?=[#\n])/, Keyword
 
         rule %r/(export)([\t ]+)(?=[\w\${}()\t -]+\n)/ do

spec/visual/samples/make

@@ -92,6 +92,14 @@ else
 THING2 = default
 endif
 
+ifeq ($(OS), Linux)
+MES = "Hi, Linux"
+else ifeq ($(OS), Darwin)
+MES = "Hi, Mac"
+else
+MES = "Unknown"
+endif
+
 ifeq ($(TARGET),special) # syntax variant: parentheses and separating comma
 TARGET = something_else
 else