Add one alias to "oras manifest fetch"

[FeynmanZhou]

What is the version of your ORAS CLI

v1.2.0

What would you like to be added?

oras manifest fetch supports viewing the metadata of a manifest. Literally, fetch might not be very straightforward for the view operation here. Suggest adding one alias oras manifest show to oras manifest fetch for usability.

Why is this needed for ORAS?

Avoid misunderstanding of oras manifest fetch and make the meaning of command more straightforward.

Are you willing to submit PRs to contribute to this feature?

• Yes, I am willing to implement it.

[Wwwsylvia]

@FeynmanZhou We have manifest get as an alias for manifest fetch. Do we still need oras manifest show and oras manifest inspect?

[shizhMSFT]

inspect is completely a different command and not suitable for being an alias.

[FeynmanZhou]

Based on the community meeting discussion and comments above, it makes more sense to add only one alias oras manifest show to oras manifest fetch for usability. I also updated the issue title and description accordingly.

cc @TerryHowe @sajayantony @oras-project/oras-cli

[FeynmanZhou]

The proposed alias has also been added to the multi-arch image management spec: https://github.com/oras-project/oras/pull/1514/files#diff-483519cec3eed7b735884e178105d6d1ee41b60492dc5354dac2ec9c37d8bb19R202

[Wwwsylvia]

I'm OK with adding oras manifest show as an additional alias for oras manifest fetch