Gorm DB.AutoMigrate migrates associated tables

GORM Playground Link

https://github.com/go-gorm/playground/pull/549

Description

DB.AutoMigrate automatically migrates associated tables, which is unexpected.

This led to an intolerable production environment accident. When I published a new feature to production it modified many existing tables.

If this is a feature but not a bug, there should be a configuration to disable it.

Example

There are two tables, T2 is associated with T1, where T1 has a content field of type varchar(xx)

type T1 struct {
    gorm.Model
    Content string
}

type T2 struct {
    gorm.Model
    T1ID uint
    T1   *T1
}

When I run the following codes

DB.AutoMigrate(&T2{})

The content field type of t1 is changed to longtext

Comment From: Nomango

gorm:"-:migration" is not working either.

E.g.

type T1 struct {
    gorm.Model
    Content string
}

type T2 struct {
    gorm.Model
    T1ID uint
    T1   *T1 `gorm:"-:migration"`
}

DB.AutoMigrate(&T2{})

T1 is always modified after migrating T2.

Is this as expected?