Add rename and rename_belongs_to for migrations.

[wout]

A proposal as suggested in #365. This makes me think about picking up #321 as well, since the same is true.

[paulcsmith]

Love it 👍

Could you add that a migration that uses these two new methods? This will test that they work when actually used with Postgres since the spec suite runs all migrations.

[wout]

Good you asked for the migration. As it turns out, you can only do one RENAME per ALTER TABLE statement. I didn't know that. 😊

https://stackoverflow.com/questions/23274679/renaming-multiple-columns-in-one-statement-with-postgresql

I chose to execute RENAME statements before ADD statements because that way you can do something like this:

alter table_for(User) do
  rename :name, :first_name
  add name : String
end

In other words, you can rename an existing column, and add a new one with the original name of the existing column, all in one migration. So, that's why I moved RENAME statements to the top.

Although not the same issue, I also included the conversion of the rename method to a macro here as well. It's a small fix in the same section of code. I hope you don't mind.

[paulcsmith]

Looks great!

[paulcsmith]

This is a really cool idea 👍

[wout]

Yeah, I was really happy with that one. 😊