option to replace attestations

[JimBugwadia]

Description

Provide a way to replace (vs. append) attestations.

Currently the same attestation type can be appended multiple times. A proposal is to support a --replace which would change the behavior to replace an attestation of the same type instead of appending it to the existing list of attestations.

Slack discussion at: https://sigstore.slack.com/archives/C01PZKDL4DP/p1633463916305100.

[JimBugwadia]

I can make the changes, if adding a --replace seems like a good approach.

[dlorenc]

We could do this on both attestations and signatures I think. It makes sense to me.

[JimBugwadia]

Thanks, @dlorenc! Please assign to me and I will work on a PR.

[developer-guy]

amazing thought @JimBugwadia 👏 , we (w/@Dentrax @erkanzileli) are available for a while, so, we can work on this issue if you let us do that 🤩

[JimBugwadia]

@developer-guy please proceed, thanks!