meta: Move metadata checks into meta directory, make them tests

This moves a few things from script/ to a new directory meta/, and makes
them real Go tests. These are the authors, copyright, metalint and gofmt
checks. That means that they can now be run by

go test -v ./meta

and optionally filtered by the usual -run thing to go test. Also -short
will cut down on the metalint stuff and exclude the authors check (which
is slow because it runs git lots of times).

Mainly this makes everything easier on things like build servers where
we can now just run tests instead of do a bunch of scripting.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4252

build.go

@@ -170,41 +170,6 @@ var targets = map[string]target{
 	},
 }
 
-var (
-	// fast linters complete in a fraction of a second and might as well be
-	// run always as part of the build
-	fastLinters = []string{
-		"deadcode",
-		"golint",
-		"ineffassign",
-		"vet",
-	}
-
-	// slow linters take several seconds and are run only as part of the
-	// "metalint" command.
-	slowLinters = []string{
-		"gosimple",
-		"staticcheck",
-		"structcheck",
-		"unused",
-		"varcheck",
-	}
-
-	// Which parts of the tree to lint
-	lintDirs = []string{".", "./lib/...", "./cmd/..."}
-
-	// Messages to ignore
-	lintExcludes = []string{
-		".pb.go",
-		"should have comment",
-		"protocol.Vector composite literal uses unkeyed fields",
-		"cli.Requires composite literal uses unkeyed fields",
-		"Use DialContext instead",   // Go 1.7
-		"os.SEEK_SET is deprecated", // Go 1.7
-		"SA4017",                    // staticcheck "is a pure function but its return value is ignored"
-	}
-)
-
 func init() {
 	// The "syncthing" target includes a few more files found in the "etc"
 	// and "extra" dirs.
@@ -285,7 +250,7 @@ func runCommand(cmd string, target target) {
 			tags = []string{"noupgrade"}
 		}
 		install(target, tags)
-		metalint(fastLinters, lintDirs)
+		metalintShort()
 
 	case "build":
 		var tags []string
@@ -293,7 +258,7 @@ func runCommand(cmd string, target target) {
 			tags = []string{"noupgrade"}
 		}
 		build(target, tags)
-		metalint(fastLinters, lintDirs)
+		metalintShort()
 
 	case "test":
 		test("./lib/...", "./cmd/...")
@@ -329,14 +294,13 @@ func runCommand(cmd string, target target) {
 		clean()
 
 	case "vet":
-		metalint(fastLinters, lintDirs)
+		metalintShort()
 
 	case "lint":
-		metalint(fastLinters, lintDirs)
+		metalintShort()
 
 	case "metalint":
-		metalint(fastLinters, lintDirs)
-		metalint(slowLinters, lintDirs)
+		metalint()
 
 	case "version":
 		fmt.Println(getVersion())
@@ -1055,59 +1019,12 @@ func macosCodesign(file string) {
 	}
 }
 
-func metalint(linters []string, dirs []string) {
-	ok := true
-	if isGometalinterInstalled() {
-		if !gometalinter(linters, dirs, lintExcludes...) {
-			ok = false
-		}
-	}
-	if !ok {
-		log.Fatal("Build succeeded, but there were lint warnings")
-	}
+func metalint() {
+	lazyRebuildAssets()
+	runPrint("go", "test", "-run", "Metalint", "./meta")
 }
 
-func isGometalinterInstalled() bool {
-	if _, err := runError("gometalinter", "--disable-all"); err != nil {
-		log.Println("gometalinter is not installed")
-		return false
-	}
-	return true
-}
-
-func gometalinter(linters []string, dirs []string, excludes ...string) bool {
-	params := []string{"--disable-all", "--concurrency=2", "--deadline=300s"}
-
-	for _, linter := range linters {
-		params = append(params, "--enable="+linter)
-	}
-
-	for _, exclude := range excludes {
-		params = append(params, "--exclude="+exclude)
-	}
-
-	for _, dir := range dirs {
-		params = append(params, dir)
-	}
-
-	bs, _ := runError("gometalinter", params...)
-
-	nerr := 0
-	lines := make(map[string]struct{})
-	for _, line := range strings.Split(string(bs), "\n") {
-		if line == "" {
-			continue
-		}
-		if _, ok := lines[line]; ok {
-			continue
-		}
-		log.Println(line)
-		if strings.Contains(line, "executable file not found") {
-			log.Println(` - Try "go run build.go setup" to install missing tools`)
-		}
-		lines[line] = struct{}{}
-		nerr++
-	}
-
-	return nerr == 0
+func metalintShort() {
+	lazyRebuildAssets()
+	runPrint("go", "test", "-short", "-run", "Metalint", "./meta")
 }