private static String generateProgressBar(double progress) {
        StringBuilder progressBar = new StringBuilder();
        progressBar.append('[');

        int barsToDisplay = (int) Math.round(PROGRESS_BAR_COUNT * progress);
        for (int barIndex = 0; barIndex < PROGRESS_BAR_COUNT; barIndex++) {
            progressBar.append(barIndex < barsToDisplay ? '=' : ' ');
        }

        return progressBar
                .append(']')
                .append(String.format(" %.1f", progress * 100))
                .append("% complete")
                .toString();
    }
Generates the progress bar line.

Taken from https://github.com/GoogleContainerTools/jib/blob/master/jib-plugins-common/src/main/java/com/google/cloud/tools/jib/plugins/common/logging/ProgressDisplayGenerator.java#L66

@param progress the overall progress, with {@code 1.0} meaning fully complete
@return the progress bar line
src/main/java/io/fabric8/maven/docker/util/JibServiceUtil.java