Preserve comments after the shebang line

The main purpose of this is to keep magic comments work.

Author: OZAWA Sakuro

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Next release
+
+* Preserve comments right after the shebang line which might include magic comments such as `frozen_string_literal: true'
+
 ## 2.0.2
 
 * Fix reloading when a watched directory contains a dangling symlink (#522)

lib/spring/client/binstub.rb

@@ -3,7 +3,7 @@
 module Spring
   module Client
     class Binstub < Command
-      SHEBANG = /\#\!.*\n/
+      SHEBANG = /\#\!.*\n(\#.*\n)*/
 
       # If loading the bin/spring file works, it'll run spring which will
       # eventually call Kernel.exit. This means that in the client process

lib/spring/test/acceptance_test.rb

@@ -260,6 +260,30 @@ def exec_name
         end
       end
 
+      test "binstub preserve magic comments" do
+        File.write(app.path("bin/rake"), <<-RUBY.strip_heredoc)
+          #!/usr/bin/env ruby
+          # frozen_string_literal: true
+          #
+          # more comments
+          require 'bundler/setup'
+          load Gem.bin_path('rake', 'rake')
+        RUBY
+
+        assert_success "bin/spring binstub rake"
+
+        expected = <<-RUBY.gsub(/^          /, "")
+          #!/usr/bin/env ruby
+          # frozen_string_literal: true
+          #
+          # more comments
+          #{Spring::Client::Binstub::LOADER.strip}
+          require 'bundler/setup'
+          load Gem.bin_path('rake', 'rake')
+        RUBY
+        assert_equal expected, app.path("bin/rake").read
+      end
+
       test "binstub upgrade with old binstub" do
         File.write(app.path("bin/rake"), <<-RUBY.strip_heredoc)
           #!/usr/bin/env ruby