finish the first version of patch_file

Gemfile

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+source "https://rubygems.org"
+
+# Declare your gem's dependencies in bulletin.gemspec.
+# Bundler will treat runtime dependencies like base dependencies, and
+# development dependencies will be added by default to the :development group.
+gemspec
+
+# Declare any dependencies that are still in development here instead of in
+# your gemspec. These might include edge Rails or gems from your path or
+# Git. Remember to move these dependencies to your gemspec before releasing
+# your gem to rubygems.org.
+
+# To use debugger
+# gem 'debugger'