Database branching: three-way merge for schema changes

This post introduces and explains the technical implementation of a three-way merge strategy for database schema changes within PlanetScale's branching system. It details how semantic diffs are generated using Vitess's `schemadiff` library and compared against a base schema (`main`) to detect conflicts between concurrent schema branches. The post provides examples of no-conflict, clear-conflict, subtle-conflict (column ordering), and nuanced-conflict (index ordering) scenarios, explaining how PlanetScale handles these to ensure safe and collaborative schema evolution.