I'm using the reusable build workflow from docker/github-builder.

When prepare creates the context for the build matrix they resulted in this type of error because the branch was updated before the workflow got to that point.

#1 [internal] load git source https://github.com/meeb/tubesync.git?ref=refs/heads/main&checksum=86e20f23a24c0f56e168be4bafa6df3cccadae02
#1 0.553 4e1fbf9e459b90bd9668f6f7bc7806d8ea959915	refs/heads/main
#1 ERROR: expected checksum to match 86e20f23a24c0f56e168be4bafa6df3cccadae02, got 4e1fbf9e459b90bd9668f6f7bc7806d8ea959915

I saw a recent pull request (#1067) that fixed this for refs/pull/, but that's not the only place that branches can be updated after all.