Merge pull request #71 from umhan35/conditionally-migrate

run `diff -q #{release_path}/db/migrate #{current_path}/db/migrate` befo...

README.md

@@ -10,6 +10,7 @@ Some rails specific options.
 ```ruby
 set :rails_env, 'staging'                  # If the environment differs from the stage name
 set :migration_role, 'migrator'            # Defaults to 'db'
+set :conditionally_migrate, true           # Defaults to false
 set :assets_roles, [:web, :app]            # Defaults to [:web]
 set :assets_prefix, 'prepackaged-assets'   # Defaults to 'assets' this should match config.assets.prefix in your rails config/application.rb
 ```

lib/capistrano/tasks/migrations.rake

@@ -5,9 +5,16 @@ namespace :deploy do
   desc 'Runs rake db:migrate if migrations are set'
   task :migrate => [:set_rails_env] do
     on primary fetch(:migration_role) do
-      within release_path do
-        with rails_env: fetch(:rails_env) do
-          execute :rake, "db:migrate"
+      conditionally_migrate = fetch(:conditionally_migrate)
+      info '[deploy:migrate] Checking changes in /db/migrate' if conditionally_migrate
+      if conditionally_migrate && test("diff -q #{release_path}/db/migrate #{current_path}/db/migrate")
+        info '[deploy:migrate] Skip `deploy:migrate` (nothing changed in db/migrate)'
+      else
+        info '[deploy:migrate] Run `rake db:migrate`' if conditionally_migrate
+        within release_path do
+          with rails_env: fetch(:rails_env) do
+            execute :rake, "db:migrate"
+          end
         end
       end
     end
@@ -18,6 +25,7 @@ end
 
 namespace :load do
   task :defaults do
+    set :conditionally_migrate, fetch(:conditionally_migrate, false)
     set :migration_role, fetch(:migration_role, :db)
   end
 end