Migration Class Names

According to the documentation you either use an incremental index or timestamp.

From what you have shown is that your trying to use the same file without incrementing
the value in the file name.

No, I'm going from 2012... to 2013... in the example above, so I'm incrementing the timestamp as the documentation says, but the timestamp is just for the file name, not the class name.

I just give more details. So, names like alter_blog_add_category, or alter_blog_remove_tags.

That's a good call. Simple.