generateTranslations runs on merges #70895

Problem

When you merge main into your PR branch, and main has changes in en.ts, translations will run on your PR, even though you didn't push any changes originating from your branch or PR.

Solution

The "traditional" solution to this is to find the merge-base between your PR head and the base branch, and then do a diff between your PR head and the merge base. The problem is that takes too long, because there's no efficient way to know how far back in the history you need to search to find the merge base.

This is a common problem, and in other repos we solve it by either:

• using fetch-depth: 0, which in E/App takes 3+ minutes
• using fetch-depth: 100, which is still kind of slow, but more importantly might arbitrarily not be deep enough.

I am cooking up a better solution.