Do not delete leading empty lines

Source code may have magic comments.

```
# frozen_string_literal: true

# == Schema Information
#
# Table name: foo
#
#  id                  :integer         not null, primary key
#  created_at          :datetime
#  updated_at          :datetime
#

class Foo < ActiveRecord::Base
end
```

In this case, the blank line before the annotation should not be erased
by `annotate --delete`.

Expected:
```
# frozen_string_literal: true

class Foo < ActiveRecord::Base
end
```

But actual:
```
# frozen_string_literal: true
class Foo < ActiveRecord::Base
end
```

This change fixes it.

Author: thinca

lib/annotate/annotate_models.rb

@@ -43,10 +43,21 @@ module AnnotateModels
 
   class << self
     def annotate_pattern(options = {})
-      if options[:wrapper_open]
-        return /(?:^(\n|\r\n)?# (?:#{options[:wrapper_open]}).*(\n|\r\n)?# (?:#{COMPAT_PREFIX}|#{COMPAT_PREFIX_MD}).*?(\n|\r\n)(#.*(\n|\r\n))*(\n|\r\n)*)|^(\n|\r\n)?# (?:#{COMPAT_PREFIX}|#{COMPAT_PREFIX_MD}).*?(\n|\r\n)(#.*(\n|\r\n))*(\n|\r\n)*/
-      end
-      /^(\n|\r\n)?# (?:#{COMPAT_PREFIX}|#{COMPAT_PREFIX_MD}).*?(\n|\r\n)(#.*(\n|\r\n))*(\n|\r\n)*/
+      nl = '(?:\n|\r\n)'
+      wrapper_pattern =
+        if options[:wrapper_open]
+          wrapper_open = options[:wrapper_open]
+          "(?:# (?:#{wrapper_open}).*#{nl}?)?"
+        else
+          ''
+        end
+      annotation_pattern = [
+        wrapper_pattern,
+        "# (?:#{COMPAT_PREFIX}|#{COMPAT_PREFIX_MD}).*?#{nl}",
+        "(?:#.*#{nl})*",
+        "#{nl}*"
+      ].join('')
+      /(?:#{annotation_pattern})|(?:^#{nl}?#{annotation_pattern}\z)/
     end
 
     def model_dir

spec/lib/annotate/annotate_models_spec.rb

@@ -2439,6 +2439,43 @@ class Foo < ActiveRecord::Base
         expect(file_content_after_removal).to eq expected_result
       end
     end
+
+    context 'when annotation is before main content and there is a magic comment' do
+      let :filename do
+        'before_with_extra_comment.rb'
+      end
+
+      let :file_content do
+        <<~EOS
+          # frozen_string_literal: true
+
+          # == Schema Information
+          #
+          # Table name: foo
+          #
+          #  id                  :integer         not null, primary key
+          #  created_at          :datetime
+          #  updated_at          :datetime
+          #
+
+          class Foo < ActiveRecord::Base
+          end
+        EOS
+      end
+
+      let :expected_result do
+        <<~EOS
+          # frozen_string_literal: true
+
+          class Foo < ActiveRecord::Base
+          end
+        EOS
+      end
+
+      it 'removes annotation but not removes leading empty lines' do
+        expect(file_content_after_removal).to eq expected_result
+      end
+    end
   end
 
   describe '.resolve_filename' do