Support filtering predecessors by artifact type on ExtendedCopy

[Wwwsylvia]

When using ExtendedCopy, clients may want to filter predecessors of a node by their artifact type. Specifically,

• Include predecessors whose artifact type matches a given regex
• Exclude predecessors whose artifact type matches a given regex

To support this, we can provide some utility methods that configure the FindPredecessors option for clients.

Original issue: #29

[Wwwsylvia]

@wangxiaoxuan273 Could you help with this?

[wangxiaoxuan273]

Sure. Please assign this to me.

[shizhMSFT]

Scenario: oras-project/oras#307

[wangxiaoxuan273]

There are several things we need to clarify:

1. ArtifactType is only supported by remote.repository and Referrers(). ExtendedCopyOptions only works on OCIDescriptors which does not support ArtifactType. Given this fact, what should be the scope of this requirement? Should the filtering only work on remote.repository? And if so, where should we check the source type? And what should be the functions' behavior on non-repository source?

[wangxiaoxuan273]

2. Should we support both inclusion and exclusion?
3. Should we support regex?

@shizhMSFT @Wwwsylvia

[shizhMSFT]

There are several things we need to clarify:

1. ArtifactType is only supported by remote.repository and Referrers(). ExtendedCopyOptions only works on OCIDescriptors which does not support ArtifactType. Given this fact, what should be the scope of this requirement? Should the filtering only work on remote.repository? And if so, where should we check the source type? And what should be the functions' behavior on non-repository source?

It is clear if the Target implements Referrers().

The question is how we can filter without referrer API for generic Targets. The solution is as simple as

1. Get the predecessors of a certain node
2. For each predecessor, check if it is an artifact manifest type. If so, read it and check its artifact type.

2. Should we support both inclusion and exclusion?

Yes. That's intersection.

3. Should we support regex?

Why not 😃

[shizhMSFT]

Resolved by #258