Ignore all symlinks

Porting the same behavior from [structure][0] and [builder][1] to this
engine.

[0]: https://github.com/codeclimate/codeclimate-structure/pull/305
[1]: https://github.com/codeclimate/builder/pull/1422

Author: wfleming

lib/cc/engine/analyzers/file_list.rb

@@ -13,9 +13,10 @@ def initialize(engine_config:, patterns:)
 
         def files
           engine_config.include_paths.flat_map do |path|
-            if path.end_with?("/")
+            pathname = Pathname.new(path)
+            if pathname.directory? && !pathname.cleanpath.symlink?
               expand(path)
-            elsif matches?(path)
+            elsif pathname.file? && !pathname.symlink? && matches?(path)
               [path]
             else
               []
@@ -30,11 +31,11 @@ def files
         def expand(path)
           globs = patterns.map { |p| File.join(relativize(path), p) }
 
-          Dir.glob(globs).select { |f| File.file?(f) }
+          Dir.glob(globs).select { |f| File.file?(f) && !File.symlink?(f) }
         end
 
         def matches?(path)
-          File.file?(path) && patterns.any? do |p|
+          patterns.any? do |p|
             File.fnmatch?(
               relativize(p),
               relativize(path),

spec/cc/engine/analyzers/file_list_spec.rb

@@ -15,13 +15,23 @@
         File.write(File.join(@tmp_dir, "foo.jsx"), "")
         File.write(File.join(@tmp_dir, "foo.ex"), "")
 
-        example.run
+        File.write("/tmp/bar.js", "")
+        FileUtils.ln_s("/tmp/bar.js", File.join(@tmp_dir, "bar.js"))
+        Dir.mkdir("/tmp/baz")
+        File.write("/tmp/baz/baz.js", "")
+        FileUtils.ln_s("/tmp/baz/", File.join(@tmp_dir, "baz"))
+
+        begin
+          example.run
+        ensure
+          FileUtils.rm_rf(["/tmp/bar.js", "/tmp/baz"])
+        end
       end
     end
   end
 
   describe "#files" do
-    it "expands patterns for directory includes" do
+    it "expands patterns for directory includes, and ignores symlinks" do
       file_list = ::CC::Engine::Analyzers::FileList.new(
         engine_config: CC::Engine::Analyzers::EngineConfig.new(
           "include_paths" => ["./"],