de_CH does not seem to be supported on Transifex, but the differences to German (Germany) are small. The de_CH.po only contains the strings with differences, gettext will automatically fallback to "de" for the rest.
Translations
Picard translations are handled by Transifex.
Please do not manually edit the PO files.
Required tools
Picard source tree strings
Their translations are handled at https://www.transifex.com/projects/p/musicbrainz/resource/picard/
One can update picard.pot using:
$ python setup.py regen_pot_file
Transifex will automatically pick picard.pot from Picard git repository master branch once per day.
Attributes and countries strings
Their translations are handled at https://www.transifex.com/projects/p/musicbrainz/resource/attributes/ and https://www.transifex.com/projects/p/musicbrainz/resource/countries/
attributes.pot and countries.pot are updated by musicbrainz-server project, outside the Picard project.
Picard maintainers can regenerate picard/const/attributes.py and picard/const/countries.py, which are using attributes.pot and countries.pot as base, using the command:
$ python setup.py update_constants
It will retrieve and parse latest attributes.pot and countries.pot to rebuild picard/const/attributes.py and picard/const/countries.py.
To fetch latest translations from Transifex
Use the following command:
$ python setup.py get_po_files
It will fetch all po files from Transifex, but the most incomplete ones.
The minimum acceptable percentage of a translation in order to download it can be seen using:
$ python setup.py get_po_files --help
The percentage value is passed to the tx pull command.