The error returned from the stdlib's `exec` package is always a message with
the exit code of the exec'd process, not any error message that process might
have given us. This results in opaque failures for the Nomad user. Cast to an
`ExitError` so that we can access the output from stderr.
Looks like the latest `github.com/docker/docker/registry.ResolveAuthConfig` expect
`github.com/docker/docker/api/types.AuthConfig` rather than
`github.com/docker/cli/cli/config/types.AuthConfig`. The two types are
identical but live in different packages.
Here, we embed `registry.ResolveAuthConfig` from upstream repo, but with
the signature we need.
Using the API as provided from the `mounts` package imposes validation
on the `src:dest` which shouldn't be performed at this time. To workaround
that lift the internal code from that library required to only perform
the split.
Support Docker `volumes` field in Windows. Previously, volumes parser
assumed some Unix-ism (e.g. didn't expect `:` in mount paths).
Here, we use the Docker parser to identify host and container paths.
Docker parsers use different validation logic from our previous unix
implementation: Docker parser accepts single path as a volume entry
(parsing it as a container path with auto-created volume) and enforces
additional checks (e.g. validity of mode). Thereforce, I opted to use
Docker parser only for Windows, and keep Nomad's linux parser to
preserve current behavior.
