Add a way to specify dependency versions for all packages in mono_repo.yaml.

[ykmnkmi]

To use with mono_repo pub get and mono_repo pub upgrade.

[jakemac53]

Just to try and fill out how this feature might work, here is one idea:

• Add a top level packages field to mono_repo.yaml. Or possibly a new file (mono_repo.packages.yaml?).
  • This would have the same format as a dependencies section in a pubspec.
• The mono_repo generate command would modify all pubspec.yaml files in the repo to fill in the version constraint listed in this file for each dependency.
  • It would probably fail if a sub-package depends on a package not listed in this global list, and ask you to add it. Or if we got really fancy prompt if you want to add it.
• Update the mono_repo validate command to ensure all the pubspecs were up to date (may get this for free?).
• The mono_repo pub <command> commands continue to work as they do today, but get consistent versions.

[ykmnkmi]

Not only dependenies from pub.dev, but also git dependencies with certain commits. Currently, I am doing this manually, and it's not the first time.

I'm not sure where this feature would be most suitable, maybe pub feature: mono_repo pub upgrade --from-file=../root_pubspec.yaml.

[jakemac53]

The process I described above could work fine for git, path, or pub dependencies. It would just blindly copy the value, which could be anything.