1 files changed, 41 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..1d34c68074
--- /dev/null
+++ b/railties/lib/rails/commands/credentials/credentials_command/diffing.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+module Rails::Command::CredentialsCommand::Diffing # :nodoc:
+  def enroll_project_in_credentials_diffing
+    if enrolled?
+      true
+    else
+      gitattributes.write(<<~end_of_template, mode: "a")
+        config/credentials/*.yml.enc diff=rails_credentials
+        config/credentials.yml.enc diff=rails_credentials
+      end_of_template
+
+      say "Project successfully enrolled!"
+      say "Rails ensures the rails_credentials diff driver is set when running `credentials:edit`. See `credentials:help` for more."
+    end
+  end
+
+  def ensure_rails_credentials_driver_is_set
+    set_driver if enrolled? && !driver_configured?
+  end
+
+  private
+    def enrolled?
+      gitattributes.read.match?(/config\/credentials(\/\*)?\.yml\.enc diff=rails_credentials/)
+    rescue Errno::ENOENT
+      false
+    end
+
+    def driver_configured?
+      system "git config --get diff.rails_credentials.textconv", out: File::NULL
+    end
+
+    def set_driver
+      puts "running"
+      system "git config diff.rails_credentials.textconv 'bin/rails credentials:diff'"
+    end
+
+    def gitattributes
+      Rails.root.join(".gitattributes")
+    end
+end