# Baselines

A build is compared with the newest approved build in its own git history. Your default branch keeps that history approved.

## How the baseline is picked

1. The CLI sends the commit's history, up to 100 commits. The server walks it from the newest commit and takes the first build of the same suite that was approved or had no changes.
2. If none matches, for example after a shallow clone, the server asks GitHub which of the newest builds on the baseline branch are in the commit's history, and takes the newest.
3. If there is still none, the build has no baseline. Every snapshot is added and the build is approved on its own, so it becomes the first baseline. The build page shows "First build, no baseline" next to Baseline.

For a new pull request, the baseline is usually the last build on the branch it started from. After you approve a build on the pull request, the next push compares with that build, so you only review what changed since.

Builds uploaded with `--subset` and builds over the storage limit are never baselines.

## The default branch

Builds on your default branch are approved on their own, reviewed or not, and become the newest baseline. To add other branches, like `release/*`, edit Auto-approve branches in the project settings. `*` matches inside one path segment and `**` across segments. It applies to builds that are not on a pull request.

## After a merge

Squash, rebase and merge commits all work. After a squash or rebase merge the new commit on the default branch is not a descendant of the pull request, so stateofpixel asks GitHub which pull request it came from. The build page shows "From PR #123" with a link to the pull request's last build, and marks changes that were never approved on that pull request as "not reviewed on PR".

## The Baselines page

The project's Baselines page, under the project in the sidebar, shows the newest approved image of every snapshot on the default branch, per suite. Type in the search box to show the snapshots whose name starts with that text. It matches upper and lower case exactly. With more than one suite, the Suite menu picks one.

Open a snapshot to see its history: up to 50 builds on the default branch where its image changed, from the last 100 builds of that branch, and who approved each one when that is known. Pick two builds to compare them in the viewer, the older one as the baseline. The two newest are picked when the page opens.

See [Reviewing changes](https://stateofpixel.com/docs/review.md) for how approvals carry over between pushes.