Display process-specific working directories when available

[jromero]

Acceptance Criteria

When a user runs pack inspect <app-image>
Then the output should include a new column under "Processes:" called "WORK DIR" for each process type listed

Proposed Solution

1. Inspect the app image's configuration for a label io.buildpacks.build.metadata
2. For each process type in the contents look for working-directory property
3. Display that working-directory property in a WORK DIR column.

NOTE: If label information is not present fallback to looking at the Config property WorkingDir:

docker inspect my-app | jq -r '.[0].Config'
{
  ...
  "WorkingDir": "/workspace",
  ...
  "Labels": {
    ...
  }
}

References

• [RFC 0081] Add process-specific working directories to io.buildpacks.build.metadata label  spec#216
• Process specific working directory spec#290

[imnitishng]

I'd like to work on this 😃