oras version

[shizhMSFT]

Run oras version to print the version.

$ bin/linux/amd64/oras version
Version:        0.4.0+unreleased
Go version:     go1.11.1
Git commit:     04121d7b0c35b067a1c58dd5ff42a0006358bc76
Git tree state: clean

Resolves #49

[bacongobbler]

The downside to this approach will be how client libraries use oras. This package will be completely useless outside of a CLI context because the version fields are generated as runtime compile flags, so exposing it as a pkg won't be very useful for others.

Perhaps it'd be better to make this package internal like we're doing in Helm 3. See https://github.com/helm/helm/blob/dev-v3/internal/version/version.go

[jdolitsky]

@bacongobbler the code looks pretty similar - are you just suggesting to add a public Get() method vs. having public vars like Version etc?

[bacongobbler]

No, I'm suggesting moving pkg/version to internal/version. Helm or other packages can't use this package unless those variables were part of the package as a constant rather than injected at compile time through compiler flags.

[shizhMSFT]

/test