Add filter to oras repo tags to filter by sha or tag

[TerryHowe]

What is the version of your ORAS CLI

1.0.0

What would you like to be added?

It would be convenient to have a filter for oras repo tags to get all the tags associated with a digest. Something like:

 oras repo tags ${REGISTRY}/curated-packages/prometheus/prometheus@sha256:c551125a624189cece9135981621f3f3144564ddabe14b523507bf74c2281d9b

Optionally, provide a tag and list other tags associated with the same tag

oras repo tags ${REGISTRY}/curated-packages/prometheus/prometheus:latest

Why is this needed for ORAS?

I want to know the version of the latest or I want to know the version associated with a digest

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

• Yes, I am willing to implement it.

[TerryHowe]

Implemented a simple WIP which works for digests.

[shizhMSFT]

The idea is great. However, we still need to consider the performance.

According to #800 (comment), docker.io/library/alpine has 129 tags. Filtering requires roughly 47 seconds. Since the time complexity is linear to the number of tags in the repository, it is estimated to take 6 mins to filter a repo of 1,000 tags.

As @qweeah has suggested, we may want to

1. Introduce --concurreny flag to accelerate the process.
2. Users need to be warned for long running command.
3. This feature is required to marked as experimental due to UX concerns.

[sajayantony]

There are throttling issues to consider since registries typically throttle the tag listing API. Also we should consider outputting a progress like curl so that users know that there is something happening rather than waiting for a long time. Higher concurrency may result in 429s easily.

[TerryHowe]

I order to support concurrency, most likely need to add support for it in oras-go oras-project/oras-go#445

[shizhMSFT]

I order to support concurrency, most likely need to add support for it in oras-go oras-project/oras-go#445

Tag listing cannot be done in parallel but the process of resolving a tag to a digest can.

[qweeah]

I order to support concurrency, most likely need to add support for it in oras-go oras-project/oras-go#445

Tag listing cannot be done in parallel but the process of resolving a tag to a digest can.

Does it mean oras-go will support resolving multiple references with tuned concurrency option in the future, and oras CLI can leverage that?