func createBuildContext()

in command-runner/internal/containers/docker/docker_build.go [69:114]
32 lines of code
8 McCabe index (conditional complexity)

func createBuildContext(ctx context.Context, contextDir string, relDockerfile string) (io.ReadCloser, error) {
	log.Ctx(ctx).Debug().Msgf("Creating archive for build context dir '%s' with relative dockerfile '%s'", contextDir, relDockerfile)

	// And canonicalize dockerfile name to a platform-independent one
	relDockerfile = filepath.ToSlash(relDockerfile)

	f, err := os.Open(filepath.Join(contextDir, ".dockerignore"))
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	defer f.Close()

	var excludes []string
	if err == nil {
		excludes, err = ignorefile.ReadAll(f)
		if err != nil {
			return nil, err
		}
	}

	// If .dockerignore mentions .dockerignore or the Dockerfile
	// then make sure we send both files over to the daemon
	// because Dockerfile is, obviously, needed no matter what, and
	// .dockerignore is needed to know if either one needs to be
	// removed. The daemon will remove them for us, if needed, after it
	// parses the Dockerfile. Ignore errors here, as they will have been
	// caught by validateContextDirectory above.
	var includes = []string{"."}
	keepThem1, _ := patternmatcher.Matches(".dockerignore", excludes)
	keepThem2, _ := patternmatcher.Matches(relDockerfile, excludes)
	if keepThem1 || keepThem2 {
		includes = append(includes, ".dockerignore", relDockerfile)
	}

	compression := archive.Uncompressed
	buildCtx, err := archive.TarWithOptions(contextDir, &archive.TarOptions{
		Compression:     compression,
		ExcludePatterns: excludes,
		IncludeFiles:    includes,
	})
	if err != nil {
		return nil, err
	}

	return buildCtx, nil
}