private String getFilePathsCommaSeparated(File[] files) {
        StringBuilder sb = new StringBuilder();
        if (files.length > 0) {
            sb.append(files[0].getAbsolutePath());
            for (int i = 1; i < files.length; i++) {
                sb.append(", ");
                sb.append(files[i].getAbsolutePath());
            }
        }
        return sb.toString();
    }
A @{link ConfigDefinitionDir} contains a set of config definitions. New definitions may be added,
but they cannot conflict with the existing ones.

@author Ulf Lilleengen
config-application-package/src/main/java/com/yahoo/config/application/ConfigDefinitionDir.java