[errors] Greatly simplify common/errors package.

logdog/appengine/coordinator/endpoints/logs/get.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package logs
 
 import (
         "time"
 
         "github.com/luci/luci-go/common/errors"
@@ skipping 122 matching lines @@
         }
         if !tail && req.LogCount < 0 && !signingRequest.HasWork() {
                 // No log operations are acutally needed, so don't bother instanting our
                 // Storage instance only to do nothing.
                 return nil
         }
 
         svc := coordinator.GetServices(c)
         st, err := svc.StorageForStream(c, lst)
         if err != nil {
-                return errors.Annotate(err).InternalReason("failed to create storage instance").Err()
+                return errors.Annotate(err, "").InternalReason("failed to create storage instance").Err()
         }
         defer st.Close()
 
         project, path := coordinator.Project(c), ls.Path()
 
         if tail {
                 resp.Logs, err = getTail(c, st, project, path)
         } else if req.LogCount >= 0 {
                 byteLimit := int(req.ByteCount)
                 if byteLimit <= 0 || byteLimit > getBytesLimit {
                         byteLimit = getBytesLimit
                 }
 
                 resp.Logs, err = getHead(c, req, st, project, path, byteLimit)
         }
         if err != nil {
                 log.WithError(err).Errorf(c, "Failed to fetch log records.")
                 return err
         }
 
         // If we're requesting a signedl URL, try and get that too.
         if signingRequest.HasWork() {
                 signedURLs, err := st.GetSignedURLs(c, &signingRequest)
                 switch {
                 case err != nil:
-                        return errors.Annotate(err).InternalReason("failed to generate signed URL").Err()
+                        return errors.Annotate(err, "").InternalReason("failed to generate signed URL").Err()
 
                 case signedURLs == nil:
                         log.Debugf(c, "Signed URL was requested, but is not supported by storage.")
 
                 default:
                         resp.SignedUrls = &logdog.GetResponse_SignedUrls{
                                 Expiration: google.NewTimestamp(signedURLs.Expiration),
                                 Stream:     signedURLs.Stream,
                                 Index:      signedURLs.Index,
                         }
@@ skipping 114 matching lines @@
                 return []*logpb.LogEntry{le}, nil
 
         case storage.ErrDoesNotExist:
                 return nil, nil
 
         default:
                 log.WithError(err).Errorf(c, "Failed to fetch tail log.")
                 return nil, err
         }
 }