Intro

The snapshot history feature allows you to click on a preview from your app's snapshots and select "See History". We try to keep track of individual previews for in your app uploads and their changes over time!

This feature requires that your builds have the upload metadata field previousSha set.

This field will allow us to create a chain of relationships between uploads and create a history:

1. starting a given upload
2. for a specific preview

Try this out by going to one of your snapshot tests, hovering over the preview you're interested in, and selecting "See History":

If you select the "view diff" button, you can see compare the changes between the two snapshots.

Why do you need previousSha ? Isn't baseSha enough? And aren't we uploading in order already?

Unfortunately just trying to use the chronological order of uploads is not reliable, since uploads can be submitted out of order.

As for baseSha, baseSha is only included for builds where comparison is intended (ex. a pull request). For "regular" uploads like those for main branch commits, all that is typically included is sha. The only way to get commit history from common source control tools like Github is by granting full source code access (sad, right?), which we obviously don't want to require. Thus, if you just include the previousSha value, we can stitch together the history by recursively finding the parent for each upload.

Beta Launch Note

As part of this initial launch, this feature will have a maximum look back of 1000 builds from the selected starting one. We will hopefully get rid of this limitation, but to ensure performance, we're starting with this guardrail.