End result are four files which contain message keys that

• are not translated (missing-translations)
• are translated but obsolete, i.e. keys being translated are no longer used (obsolete-translations)
• have duplicate declarations (duplicate-keys)
• have duplicate translations (duplicate-translations)
• have same keys declared in old i18n mechanism and new one (duplicate-keys-potential)
• have same translated keys in old i18n mechanism and new one (duplicate-translations-potential)

To use this script, you have to clone all git repositories (note that currently shop and processed-resources are only two FORGE modules translated - delete all others modules)