This is Signal's fork of libPhoneNumber-iOS, which is an Objective-C port of Google's libphonenumber.

If you want the latest metadata from libphonenumber...

1. Clone this fork.
2. Determine the version of libphonenumber (not libPhoneNumber-iOS) that you want to pull metadata from. For example, v1.2.3. You may wish to visit the libphonenumber repo.
3. From the project root, run LIBPHONENUMBER_REF=v1.2.3 make update_metadata, replacing the variable with whatever version you want. This script fetches metadata from the libphonenumber repo and updates a few files in this one. Most notably, it changes libPhoneNumber/NBPhoneNumberMetaData.plist.
4. Commit the changes to the signal-master and push the changes.

From there, you can update the dependency in the Signal iOS project as normal, likely using bundle exec pod update libPhoneNumber-iOS.