Refactor building default globs

spec/ameba/config_spec.cr

@@ -20,7 +20,7 @@ module Ameba
           File.touch "lib/shard.cr"
           yml = YAML.parse "{}"
           config = Config.new(yml)
-          config.globs.should eq Config::DEFAULT_GLOBS
+          config.globs.should eq ["**/*.cr", "!lib"]
           File.delete "lib/shard.cr"
         end
       end

src/ameba/config.cr

@@ -55,10 +55,7 @@ class Ameba::Config
     Path[XDG_CONFIG_HOME] / "ameba/config.yml",
   }
 
-  DEFAULT_GLOBS = %w(
-    **/*.cr
-    !lib
-  )
+  SOURCES_GLOB = "**/*.cr"
 
   getter rules : Array(Rule::Base)
   property severity = Severity::Convention
@@ -240,9 +237,8 @@ class Ameba::Config
   end
 
   private def default_globs
-    DEFAULT_GLOBS.select do |glob|
-      !Dir[glob].empty? ||
-        (glob.starts_with?("!") && !Dir["#{glob[1..-1]}/**/*.cr"].empty?)
+    [SOURCES_GLOB].tap do |globs|
+      globs.push("!lib") if !Dir["lib/**/*.cr"].empty?
     end
   end