chore: improve error message if the provided annotation file is inval…

…id (#1255)

Signed-off-by: Xiaoxuan Wang <[email protected]>

cmd/oras/internal/option/packer.go

@@ -100,13 +100,10 @@ func (opts *Packer) LoadManifestAnnotations() (annotations map[string]map[string
 	}
 	if opts.AnnotationFilePath != "" {
 		if err = decodeJSON(opts.AnnotationFilePath, &annotations); err != nil {
-			errStr := err.Error()
-			docLink := " Please refer to the document at https://oras.land/docs/how_to_guides/manifest_annotations."
-			if !strings.HasSuffix(errStr, ".") {
-				docLink = "." + docLink
+			return nil, &oerrors.Error{
+				Err:            fmt.Errorf(`invalid annotation json file: failed to load annotations from %s`, opts.AnnotationFilePath),
+				Recommendation: `Annotation file doesn't match the required format. Please refer to the document at https://oras.land/docs/how_to_guides/manifest_annotations`,
 			}
-			return nil, fmt.Errorf("failed to load annotations from %s: %w"+
-				docLink, opts.AnnotationFilePath, err)
 		}
 	}
 	if len(opts.ManifestAnnotations) != 0 {