Rename to Diffing and move module into credentials command

Helpers is more for sharing between commands. Since `Diffing` is only
for credentials we should just keep it only for credentials.

Replaces "pretty" with diffing since the former is ambiguous, while
diffing captures what it does. `opt_in` seemed clunky so it's swapped
for the one-word enable.

1 files changed, 49 insertions, 0 deletions

diff --git a/railties/lib/rails/commands/credentials/credentials_command/diffing.rb b/railties/lib/rails/commands/credentials/credentials_command/diffing.rb
new file mode 100644
index 0000000000..715dd06ea4
--- /dev/null
+++ b/railties/lib/rails/commands/credentials/credentials_command/diffing.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require "fileutils"
+
+module Rails::Command::CredentialsCommand::Diffing # :nodoc:
+  class Error < StandardError; end
+
+  def enable_credentials_diffing
+    unless already_answered? || enabled?
+      answer = yes?("Would you like to make the credentials diff from git more readable in the future? [Y/n]")
+    end
+
+    enable if answer
+    FileUtils.touch(tracker) unless answer.nil?
+  rescue Error
+    say "Couldn't setup git to enable credentials diffing"
+  end
+
+  private
+    def already_answered?
+      tracker.exist?
+    end
+
+    def enabled?
+      system_call("git config --get 'diff.rails_credentials.textconv'", accepted_codes: [0, 1])
+    end
+
+    def enable
+      system_call("git config diff.rails_credentials.textconv 'bin/rails credentials:show'", accepted_codes: [0])
+
+      git_attributes = Rails.root.join(".gitattributes")
+      File.open(git_attributes, "a+") do |file|
+        file.write(<<~EOM)
+          config/credentials/*.yml.enc diff=rails_credentials
+          config/credentials.yml.enc diff=rails_credentials
+        EOM
+      end
+    end
+
+    def tracker
+      Rails.root.join("tmp", "rails_pretty_credentials")
+    end
+
+    def system_call(command_line, accepted_codes:)
+      result = system(command_line)
+      raise(Error) if accepted_codes.exclude?($?.exitstatus)
+      result
+    end
+end