Which GitHub features are needed in a code forge before you can migrate?

Which GitHub features would you consider a blocker for migrating to a different code forge, and in what order do you prioritize them?

Context:

I am heads down building a code forge (juju.bi) based on three ideas:

• Code collaboration part should work offline

• Should be compatible with GitHub API (like how some services are considered S3 compatible)

• Support change-id based features (ex: Jujutsu's evolog)

I shipped a super-early version that I am currently dogfooding. juju.bi/changelog/2026-07-01-alpha-release

I am currently focused on improving the experience for small teams working on private repos. I would like to polish the overall product before thinking about public repos. (A lot of great forges exist for public repos right now).