return success when force deleting a non-existent blob/manifest

[qweeah]

When force deleting via oras manifest/blob delete, if the target reference is not found in the remote registry, then user will see an error message like below:

$ oras blob delete localhost:5000/command/blob/delete/1671102430@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa --force
Error: localhost:5000/command/blob/delete/1671102430@sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: the specified blob does not exist

The returned value should indicate success if successfully resolving the reference and registry returns not found.

@FeynmanZhou

[shizhMSFT]

Here are the exit codes of the rm command for references.

$ rm not-exist
rm: cannot remove 'not-exist': No such file or directory
$ echo $?
1
$ rm -f not-exist
$ echo $?
0
$ rm /dev/null
rm: cannot remove '/dev/null': Permission denied
$ echo $?
1
$ rm -f /dev/null
rm: cannot remove '/dev/null': Permission denied
$ echo $?
1

[FeynmanZhou]

Agree to change the return to success in the case above. How can we describe the output message exactly?

[qweeah]

Taking manifest delete as an example, suppose $IMAGE is not existed:

• oras manifest delete $IMAGE -f

  • return success since -f implies forced action
  • output Missing $IMAGE to stdout, this UX is consistent with deleting an existent manifest

• oras manifest delete $IMAGE

  • fail and output Error: $IMAGE: the specified manifest does not exist to stderr

• oras manifest delete $IMAGE -f --descriptor

  • fail since the to-be-deleted descriptor doesn't exist
  • output Error: $IMAGE: the specified manifest does not exist to stderr