Flat changelog items

[geoffreylitt]

This is a major refactor of the ReviewSidebar timeline view.

Previously we were rendering a list of ChangeGroups, and some had associated markers. This led to very messy UI structure and difficulty handling things like selection state.

This PR reworks the data structures so that we have a flat list of ChangelogItems which each represent a change group, a milestone, a branch creation, a branch merge, a comment, etc. Selection is handled in a much cleaner way; it's just a linear selection in that list.

Every ChangelogItem has a unique id, a doc heads, a list of users associated w/ that item, and a timestamp. This lets us uniformly render common elements across entries in the log.

export type ChangelogItem = {
  id: string;
  heads: Heads;
  users: AutomergeUrl[];
  time: number;
} & ({ type: "changeGroup"; changeGroup: ChangeGroup } | HeadsMarker);

[netlify]

✅ Deploy Preview for tee-production ready!

Name	Link
🔨 Latest commit	77b448d
🔍 Latest deploy log	https://app.netlify.com/sites/tee-production/deploys/65dfbc42755d410008f1e610
😎 Deploy Preview	https://deploy-preview-32--tee-production.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.