[errors] Greatly simplify common/errors package.

logdog/client/cli/subcommandCat.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 cli
 
 import (
         "io"
         "os"
         "strconv"
@@ skipping 103 matching lines @@
                         log.Fields{
                                 log.ErrorKey: err,
                                 "index":      i,
                                 "project":    addr.Project,
                                 "path":       addr.Path,
                         }.Errorf(a, "Invalid command-line stream path.")
                         return 1
                 }
 
                 if addr.Host, err = a.resolveHost(""); err != nil {
-                        err = errors.Annotate(err).Reason("failed to resolve host: %(host)q").
-                                D("host", addr.Host).Err()
+                        err = errors.Annotate(err, "failed to resolve host: %q", addr.Host).Err()
                         errors.Log(a, err)
                         return 1
                 }
 
                 addrs[i] = &addr
         }
         if cmd.buffer <= 0 {
                 log.Fields{
                         "value": cmd.buffer,
                 }.Errorf(a, "Buffer size must be >0.")
         }
 
         coords := make(map[string]*coordinator.Client, len(addrs))
         for _, addr := range addrs {
                 if _, ok := coords[addr.Host]; ok {
                         continue
                 }
 
                 var err error
                 if coords[addr.Host], err = a.coordinatorClient(addr.Host); err != nil {
-                        err = errors.Annotate(err).Reason("failed to create Coordinator client for %(host)q").
-                                D("host", addr.Host).Err()
+                        err = errors.Annotate(err, "failed to create Coordinator client for %q", addr.Host).Err()
 
                         errors.Log(a, err)
                         return 1
                 }
         }
 
         tctx, _ := a.timeoutCtx(a)
         for i, addr := range addrs {
                 if err := cmd.catPath(tctx, coords[addr.Host], addr); err != nil {
                         log.Fields{
@@ skipping 97 matching lines @@
                 }
 
                 if err := proto.MarshalText(w, pb); err != nil {
                         log.WithError(err).Errorf(c, "Failed to marshal datagram as text.")
                         return false
                 }
 
                 return true
         }
 }