Add `git diff` to `Podfile.lock` diverged annotation

[mokagio]

I was baffled today by a test build failing because the Podfile.lock changed in CI even though running bundle exec pod install locally didn't make it change for me.

I found it useful to print the diff that triggered the failure, which revealed the code I wrote was printing absolute paths in the Podfile.lock.

In action:

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• [ ] I have considered if this change warrants release notes and have added them to the appropriate section in the CHANGELOG.md if necessary.