A build resource in the Container Builder API. At a high level, a Build describes where to find source code, how to build it (for example, the builder image to run on the source), and what tag to apply to the built image when it is pushed to Google Container Registry. Fields can include the following variables which will be expanded when the build is created: - $PROJECT_ID: the project ID of the build. - $BUILD_ID: the autogenerated ID of the build. - $REPO_NAME: the source repository name specified by RepoSource. - $BRANCH_NAME: the branch name specified by RepoSource. - $TAG_NAME: the tag name specified by RepoSource. - $REVISION_ID or $COMMIT_SHA: the commit SHA specified by RepoSource or resolved from the specified branch or tag.