Proposal: A tool to make it easier to resolve multiple versions issues

[matthewp]

tldr; create a utility to help resolve multiple versions of can package problems.

The problem

Talking to donejs developers that utilize package-lock.json, they often run into issues when upgrading one dependency such as can. The issue is caused because when you update can, and for example can-observation version has changed, it will upgrade the version in node_modules/can/node_modules/can-observation but leave the old version in the root node_modules/can-observation folder. This happens because other donejs dependencies, such as done-autorender also (indirectly) depend on these global packages.

Proposal

I propose an additional command in donejs checks for multiple versions of common dependencies and outputs information (a more detailed version of npm ls perhaps) to help developers figure out what went wrong.

If possible it would be nice if we could even fix it for them. I'm thinking something like:

> donejs doctor

*Warning* multiple versions of:
  - can-observation (4.0.0 and 4.0.3)

And running:

> donejs doctor --fix

*Warning* multiple versions of:
  - can-observation (4.0.0 and 4.0.3)

*Fixing*.....

All done!