Default of -1 (minus 1) generates useless migrations

[anodynos]

Issue type:

[ ] question
[X] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[X] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[X] latest
[ ] @next
[X] 0.2.20 (or put your version here)

Steps to reproduce or a small repository showing the problem:

See repo at https://github.com/anodynos/typeorm-bug-migrations-default-minus-1
Execute ╰─$ scripts/migration-generate.sh to reproduce the issue.

Assuming an Entity :

@Entity('foo')
export class Foo {
  ...
  @Column({ default: 1, type: 'bigint' })
  bar_default_plus_1_is_fine: number;
  
  @Column({ default: -1, type: 'bigint' })
  bar_default_minus_1_is_creating_repeated_migrations: number;
}

after the initial migration is added, every time we generate a migration (without any schema changes), we get a new migration like:

...
    public async up(queryRunner: QueryRunner): Promise<any> {
        await queryRunner.query(`ALTER TABLE "foo" ALTER COLUMN "bar_default_minus_1_is_creating_repeated_migrations" SET DEFAULT -1`, undefined);
    }

    public async down(queryRunner: QueryRunner): Promise<any> {
        await queryRunner.query(`ALTER TABLE "foo" ALTER COLUMN "bar_default_minus_1_is_creating_repeated_migrations" SET DEFAULT '-1'`, undefined);
    }
...