feat: --dev flag for codegen (#555)

---------

Co-authored-by: ken-kost <[email protected]>

Author: zachdaniel

config/config.exs

@@ -37,6 +37,14 @@ if Mix.env() == :test do
     hostname: "localhost",
     pool: Ecto.Adapters.SQL.Sandbox
 
+  config :ash_postgres, AshPostgres.DevTestRepo,
+    username: "postgres",
+    password: "postgres",
+    database: "ash_postgres_dev_test",
+    hostname: "localhost",
+    migration_primary_key: [name: :id, type: :binary_id],
+    pool: Ecto.Adapters.SQL.Sandbox
+
   # sobelow_skip ["Config.Secrets"]
   config :ash_postgres, AshPostgres.TestRepo, password: "postgres"
 
@@ -54,7 +62,7 @@ if Mix.env() == :test do
     migration_primary_key: [name: :id, type: :binary_id]
 
   config :ash_postgres,
-    ecto_repos: [AshPostgres.TestRepo, AshPostgres.TestNoSandboxRepo],
+    ecto_repos: [AshPostgres.TestRepo, AshPostgres.DevTestRepo, AshPostgres.TestNoSandboxRepo],
     ash_domains: [
       AshPostgres.Test.Domain,
       AshPostgres.MultitenancyTest.Domain,

documentation/topics/development/migrations-and-tasks.md

@@ -7,9 +7,16 @@ Ash comes with its own tasks, and AshPostgres exposes lower level tasks that you
 ## Basic Workflow
 
 - Make resource changes
-- Run `mix ash.codegen --name add_a_combobulator` to generate migrations and resource snapshots
+- Run `mix ash.codegen --dev` to generate a migration tagged as a `dev` migration, which will later be squashed and does not require a name.
+- Run `mix ash.migrate` to run the migrations.
+- Make some more resource changes.
+- Once you're all done, run `mix ash.codegen add_a_combobulator`, using a good name for your changes to generate migrations and resource snapshots. This will **rollback** the dev migrations, and squash them into a the new named migration (or sometimes migrations).
 - Run `mix ash.migrate` to run those migrations
 
+The `--dev` workflow enables you to avoid having to think of a name for migrations while developing, and also enables some
+upcoming workflows that will detect when code generation needs to be run on page load and will show you a button to generate
+dev migrations and run them.
+
 For more information on generating migrations, run `mix help ash_postgres.generate_migrations` (the underlying task that is called by `mix ash.migrate`)
 
 > ### list_tenants/0 {: .info}