[5.3] Touch owners on save only if model is dirty

[dan-har]

It seems that the model save() method not behave correctly when saving model that is NOT dirty and the model set to touch its owners.

So lets say we have posts and comments

$comment = Comment::find(1);

// do something ...

// $comment->isDirty() == false

$comment->save();

/** owner post timestamp is updating **/

It results with the saved model updated_at attribute not changing but the owner model updated_at is changed.

This is a suggestion for fixing this issue. In this change the save method will return false if the model is not dirty.

[kasparsklavins]

This would be a breaking change as I rely on this behaviour when changing user associated data in the filesystem.

[dan-har]

For updating timestamps, a more explicit way may be $model->touch().

The problem with this behavior is that leads to non consistent data being saved in the database whether someone aware to it or not.

[GrahamCampbell]

This would be a breaking change

That's fine. Laravel 5.3 is allowed breaking changes wrt 5.2.