In Dart and Pub, should I add pubspec.lock to my .gitignore?
This answer has two parts, similarly to the question and answer in this question about Ruby bundler.
Application packages
If you are working on an application package, then you should keep the pubspec.lock file in your repository as a snapshot of your dependencies.
From the Pub glossary:
Application packages should check their lockfiles into source control,so that everyone working on the application and every location theapplication is deployed has a consistent set of dependencies.
Library packages
However, if you are working on a library package, then you should not check in the lockfile.
From the Pub glossary:
Library packages should not check their lockfile into source control,since they should support a range of dependency versions.
See also the Pub glossary entry for lockfiles