asdf info should show sha's of plugins and distance behind their remotes

[jthegedus]

Is your feature request related to a problem? Please describe.

asdf info is really useful information to debug with, however, the list of plugins is less useful as we do not know any statistics about the plugin state

Describe the solution you'd like

I would like to print both:

• the sha or ref of the checked-out plugin
• the distance (commits) behind the default branch of the plugin repo

Distance might suffice, though ref would be useful once we have plugin versioning support.

Describe similar asdf features and why they are not sufficient

Describe workarounds you've considered

We usually ask people to update their plugins and the asdf core and investigate if their issue still persists.

Additional context

• Notify users of core or plugin updates - Notify users of core or plugin updates #725
• Add versioning to plugin add command - feat: Add versioning to plugin add command #916

[jthegedus]

I think implementing distance (commits) behind the remote will be a lot of work to implement, especially when we have --refs already to leverage and get half of this feature for little dev cost.

[Stratus3D]

Yeah, I think just displaying the refs would help us a lot and be very easy to implement.