So you know one guy that quit over having and ORM instead of using SQL... do you have any idea how many quit due having to deal with thousands of lines of SQL string concatenations because some genius that also hates ORMs decided to do a giant project that way?
Then you call your alternative anti-orm and it generates... orm specs, and then you say "migration commands based on the git history"... what does that even mean? What does git history has to do with the database?
I'm not sure what git-specific interaction the author is envisioning, but more generally: declarative schema management tools are based on the notion of using a repo to store only CREATE statements. It's an infrastructure-as-code style approach, where to modify an existing table, you just modify the CREATE definition. The tool figures out how to translate this to an ALTER.
I'm the author of an existing tool in this space, Skeema [1], which supports MySQL and MariaDB. Other recent tools in this space include migra [2] and sqldef [3]. From what I understand, in the SQL Server world there are a number of others.