Add istidy check

common.go

@@ -99,6 +99,33 @@ func (cmd Common) VendorModules() {
 	ErrFatalf(err, "go mod vendor failed: %v\n", err)
 }
 
+func (cmd Common) Tidy() {
+	fmt.Fprintf(os.Stderr, "# Tidying modules\n")
+
+	workdir, err := os.Getwd()
+	ErrFatalf(err, "unable to get working directory: %v\n", err)
+
+	defer func() {
+		err = os.Chdir(workdir)
+		ErrFatalf(err, "unable to change directory: %v\n", err)
+	}()
+
+	err = os.Chdir(cmd.RepoDir())
+	ErrFatalf(err, "unable to change directory: %v\n", err)
+
+	for repeat := 2; repeat > 0; repeat-- {
+		gomod := exec.Command("go", "mod", "tidy", "-v")
+		gomod.Env = append(os.Environ(), "GO111MODULE=on")
+		gomod.Stdout, gomod.Stderr = os.Stderr, os.Stderr
+		err = gomod.Run()
+		Errf(err, "go mod tidy failed, retrying: %v\n", err)
+		if err == nil {
+			break
+		}
+	}
+	ErrFatalf(err, "go mod tidy failed: %v\n", err)
+}
+
 func (cmd Common) DeleteVendor() {
 	fmt.Fprintf(os.Stderr, "# Deleting vendor\n")
 

main.go

@@ -85,6 +85,7 @@ func main() {
 		&Update{Common: common},
 		// &Cache{Common: common},
 
+		&IsTidy{Common: common},
 		&Hash{Common: common},
 		&ZipVendor{Common: common},
 		&UnzipVendor{Common: common},

mod.go

@@ -0,0 +1,39 @@
+// Copyright (C) 2018 Storj Labs, Inc.
+// See LICENSE for copying information.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+type IsTidy struct {
+	Common
+}
+
+func (cmd *IsTidy) Name() string { return "istidy" }
+
+func (cmd *IsTidy) Parse(args []string) error {
+	set := flag.NewFlagSet(cmd.Name(), flag.ExitOnError)
+	return set.Parse(args)
+}
+
+func (cmd *IsTidy) Exec() {
+	repodir := cmd.RepoDir()
+
+	before, err := HashFiles(filepath.Join(repodir, "go.mod"))
+	ErrFatal(err)
+
+	cmd.Tidy()
+
+	after, err := HashFiles(filepath.Join(repodir, "go.mod"))
+	ErrFatal(err)
+
+	if before != after {
+		fmt.Fprintln(os.Stderr, "go.mod is not tidy")
+		os.Exit(1)
+	}
+}