This directory includes scripts and tools for setting up Flutter's continuous integration environments.
Flutter's Linux tasks run on a custom Docker image. The Dockerfile for this image can be found at /dev/ci/docker_linux/Dockerfile. On each new change to this Dockerfile, Cirrus will build a new version of the Docker image as a dependency to any Linux tests. It is no longer necessary to manually build and push the Docker image locally.
NOTE: there are some factors external to the actual Dockerfile that would necessitate rebuilding the Docker image, such as upstream code changes, (Linux distribution) repository updates or a file that gets COPYied into the image changing. In this case, a trivial Dockerfile change (such as a comment) would invalidate the cache and trigger a rebuild.