The first thing I've looked at on your site is how migrations work. Because honestly, I think that's one of the best things about Django. They just got it right, and as you say, not many other tools get close.

I wonder if you have looked at how it works. Because they have put in something like a decade to make it work and it's very powerful and a joy to use.

Down migrations are indeed very useful and important once you get used to it. First and foremost they give you a very strong confidence in changing your schema. The last time I told someone who I helped with django to "always write the reverse migration" was yesterday.

No way you can automatically resolve the discrepancies you can get with branched development. Partially because you can use migrations to migrate the data not just to update the schema. It's pretty simple as long as we're just thinking about adding a few tables or renaming columns. You just hammer the schema into whatever the expected format is according to the migrations on that branch. But even that can go wrong: what if I introduced a NOT NULL constraint on a column in one of the branches and I want to switch over? Say my migration did set a default value to deal with it. Hammering won't help here.

The thing is that doing the way Django does it is not that hard (assuming you want to write a migration engine anyway). Maybe you've already looked at it, but just for the record:

- they don't use SQL for the migration files, but python (would be Typescript in your case). This is what they generate.
- the python files contain the schema change operations encoded as python objects (e.g. `RenameField` when a field gets renamed and thus the column has to be renamed too, etc.).
- they generate the SQL to apply from these objects

Now since the migration files themselves are built of python objects representing the needed changes, it's easy for them to have both a forward and the backward migration for each operation. Now you could say that it doesn't allow for customization, but they have two special operations. One is for running arbitrary SQL (called RunSQL (takes two params: one string for the forward and one for the backward migration) and one is for arbitrary python code (called RunPython, takes two functions as arguments: one for the forward and one for the backward migration).

One would usually use RunSQL to do the tricky things that the migration tool can't (e.g. add db constraints not supported by the ORM) and RunPython to do data migrations (when you actually need to move data around due to a schema change). And thanks to the above architecture you can actually use the ORM in the migration files to do these data migrations. Of course, you can't just import your models from your code because they will have already evolved if you replay older migrations (e.g. to set up a new db or to run tests). But because the changes are encoded as python objects, they can be replayed in the memory and the actual state valid at the time of writing the migration can be reconstructed.

And when you are creating a new migration after changing your model you are actually comparing your model to the result of this in-memory replay and not the db. Which is great for a number of reasons.