improve error message when no tag or digest provided #1211
Description
Current behavior and output:
$ oras manifest fetch --oci-layout /tmp/ginkgo1163328512
Error: "/tmp/ginkgo1163328512": no tag or digest when expecting <name:tag|name@digest>Suggested error message:
$ oras manifest fetch --oci-layout /tmp/ginkgo1163328512
Error: "/tmp/ginkgo1163328512": no tag or digest specified
Usage: oras manifest fetch [flags] <name>{:<tag>|@<digest>}
You need to specify an artifact reference in the form of "<name>:<tag>" or "<name>@<digest>". Run "oras manifest fetch -h" for more options and examples