public static ValueCombinePolicy fromString(String valueCombinePolicy) {
        for (ValueCombinePolicy policy : values()) {
            if (policy.name().equalsIgnoreCase(valueCombinePolicy)) {
                return policy;
            }
        }
        throw new IllegalArgumentException(String.format("No value combine policy %s known. Valid values are: %s",
                valueCombinePolicy, StringUtils.join(values(), ", ")));
    }
All provided values are merged. This only makes sense for complex types such as lists and maps.
src/main/java/io/fabric8/maven/docker/config/handler/property/ValueCombinePolicy.java