accepts attachment-tag-prefix for cosign copy

[mritunjaysharma394]

Summary

This PR was created in an attempt that closes #2962 where in the case of cosign copy, attachment-tag-prefix was ignored.

Release Note

Fixed cosign copy ignoring attachment-tag-prefix flag

Documentation

Nope, I guess.

[codecov]

Codecov Report

Merging #3014 (7ea5d75) into main (6236366) will increase coverage by 0.21%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##             main    #3014      +/-   ##
==========================================
+ Coverage   30.23%   30.45%   +0.21%     
==========================================
  Files         151      152       +1     
  Lines        9478     9584     +106     
==========================================
+ Hits         2866     2919      +53     
- Misses       6167     6208      +41     
- Partials      445      457      +12     

Impacted Files	Coverage Δ
cmd/cosign/cli/copy/copy.go	50.00% <66.66%> (ø)

[hectorj2f]

@mritunjaysharma394 Thanks for the PR.

Would you mind adding a test to validate the problem reported in the issue?

[mritunjaysharma394]

Hi @hectorj2f, thanks for the quick review, I was a little unsure of how to get tag/hash/digest for the test code to verify if the tag-prefix worked the way we want or not since in test-code, I assume we arent talking to the remote registry. However, I still tried to write one, feel free to review and help me with improvements, here's the debug console output which shows it works, thanks a lot:

[mritunjaysharma394]

Also @hectorj2f, I just checked it with the repro that @znewman01 mentioned while creating the issue, I followed the exact steps and it seems to be working now:

[znewman01]

LGTM except the one question I had

[znewman01]

LGTM, thank you so much!

[thangarajav]

Thanks for fixing the issue, When it will be available for me to download.

[znewman01]

Should have a new release Real Soon Now (TM): sigstore/sigstore#1166 (comment)

:)

[mattmoor]

This means we will never copy the tag itself 🤔

cc @haydentherapper

[mattmoor]

Honestly, I'm not sure what dstRepoRef.Tag(srcDigest.Identifier()) is even meant to do either 😅