cmd/oracle: improve error messages

Also, in Emacs, make 'referrers' query not prompt for a scope.

Change-Id: I5c0f034d4fa8b653311f1b7d8ff58b699d168b79
Reviewed-on: https://go-review.googlesource.com/9927
Reviewed-by: Andrew Gerrand <adg@golang.org>

cmd/oracle/main.go

@@ -176,7 +176,7 @@ func main() {
 	}
 
 	if err := oracle.Run(&query); err != nil {
-		fmt.Fprintf(os.Stderr, "oracle: %s.\n", err)
+		fmt.Fprintf(os.Stderr, "oracle: %s\n", err)
 		os.Exit(1)
 	}
 
@@ -185,7 +185,7 @@ func main() {
 	case "json":
 		b, err := json.MarshalIndent(query.Serial(), "", "\t")
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "oracle: JSON error: %s.\n", err)
+			fmt.Fprintf(os.Stderr, "oracle: JSON error: %s\n", err)
 			os.Exit(1)
 		}
 		os.Stdout.Write(b)
@@ -193,7 +193,7 @@ func main() {
 	case "xml":
 		b, err := xml.MarshalIndent(query.Serial(), "", "\t")
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "oracle: XML error: %s.\n", err)
+			fmt.Fprintf(os.Stderr, "oracle: XML error: %s\n", err)
 			os.Exit(1)
 		}
 		os.Stdout.Write(b)

cmd/oracle/oracle.el

@@ -219,7 +219,7 @@ this channel receive/send operation."
   "Enumerate all references to the object denoted by the selected
 identifier."
   (interactive)
-  (go-oracle--run "referrers" t))
+  (go-oracle--run "referrers"))
 
 (defun go-oracle-whicherrs ()
   "Show globals, constants and types to which the selected

oracle/what.go

@@ -152,7 +152,7 @@ func guessImportPath(filename string, buildContext *build.Context) (srcdir, impo
 		}
 	}
 	if srcdir == "" {
-		err = fmt.Errorf("directory %s is not beneath GOROOT or GOPATH: %s",
+		err = fmt.Errorf("directory %s is not beneath any of these GOROOT/GOPATH directories: %s",
 			filepath.Dir(absFile), strings.Join(buildContext.SrcDirs(), ", "))
 	}
 	return