build: Actually set build tags (#6866)

Apparently our Tags field depended on having specific files react to
tags and add themselves there. This, instead, works for all tags.

Also, pass tags to the test command line.

lib/build/build.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"regexp"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
 	"time"
@@ -23,6 +24,7 @@ var (
 	Host    = "unknown"
 	User    = "unknown"
 	Stamp   = "0"
+	Tags    = ""
 
 	// Static
 	Codename = "Fermium Flea"
@@ -34,9 +36,6 @@ var (
 	IsBeta      bool
 	LongVersion string
 
-	// Set by Go build tags
-	Tags []string
-
 	allowedVersionExp = regexp.MustCompile(`^v\d+\.\d+\.\d+(-[a-z0-9]+)*(\.\d+)*(\+\d+-g[0-9a-f]+)?(-[^\s]+)?$`)
 
 	envTags = []string{
@@ -88,13 +87,19 @@ func LongVersionFor(program string) string {
 	// This string and date format is essentially part of our external API. Never change it.
 	date := Date.UTC().Format("2006-01-02 15:04:05 MST")
 	v := fmt.Sprintf(`%s %s "%s" (%s %s-%s) %s@%s %s`, program, Version, Codename, runtime.Version(), runtime.GOOS, runtime.GOARCH, User, Host, date)
+
+	tags := strings.Split(Tags, ",")
+	if len(tags) == 1 && tags[0] == "" {
+		tags = tags[:0]
+	}
 	for _, envVar := range envTags {
 		if os.Getenv(envVar) != "" {
-			Tags = append(Tags, strings.ToLower(envVar))
+			tags = append(tags, strings.ToLower(envVar))
 		}
 	}
-	if len(Tags) > 0 {
-		v = fmt.Sprintf("%s [%s]", v, strings.Join(Tags, ", "))
+	if len(tags) > 0 {
+		sort.Strings(tags)
+		v = fmt.Sprintf("%s [%s]", v, strings.Join(tags, ", "))
 	}
 	return v
 }

lib/build/tags_noupgrade.go

@@ -1,13 +0,0 @@
-// Copyright (C) 2017 The Syncthing Authors.
-//
-// This Source Code Form is subject to the terms of the Mozilla Public
-// License, v. 2.0. If a copy of the MPL was not distributed with this file,
-// You can obtain one at https://mozilla.org/MPL/2.0/.
-
-//+build noupgrade
-
-package build
-
-func init() {
-	Tags = append(Tags, "noupgrade")
-}

lib/build/tags_race.go

@@ -9,5 +9,9 @@
 package build
 
 func init() {
-	Tags = append(Tags, "race")
+	if Tags == "" {
+		Tags = "race"
+	} else {
+		Tags = Tags + ",race"
+	}
 }