Check if major already exists before adding

major/major.go

@@ -62,14 +62,28 @@ func Run(dir, op, modName string, tag int) error {
 		// It would be nicer to use modFile.AddRequire
 		// and modFile.DropRequire, but they do not
 		// preserve block location.
+		var majorExists bool
 		for _, req := range modFile.Require {
-			if req.Mod.Path == modName {
-				req.Mod.Path = newModPath
-				req.Mod.Version = "latest"
+			if req.Mod.Path == newModPath {
+				majorExists = true
 				break
 			}
 		}
-		modFile.SetRequire(modFile.Require)
+		if majorExists {
+			err = modFile.DropRequire(modName)
+			if err != nil {
+				return fmt.Errorf("error dropping %q: %w", modName, err)
+			}
+		} else {
+			for _, req := range modFile.Require {
+				if req.Mod.Path == modName {
+					req.Mod.Path = newModPath
+					req.Mod.Version = "latest"
+					break
+				}
+			}
+			modFile.SetRequire(modFile.Require)
+		}
 	} else {
 		modFile.Module.Syntax.Token[1] = newModPath
 	}

migrate/migrate.go

@@ -5,7 +5,6 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"os"
@@ -76,7 +75,7 @@ type resp struct {
 
 func migrate(path string, gc *github.Client, test bool) error {
 	fmt.Printf("git clone %v\n", path)
-	tempdir, err := ioutil.TempDir("", strings.Replace(path, "/", "_", -1))
+	tempdir, err := os.MkdirTemp("", strings.Replace(path, "/", "_", -1))
 	if err != nil {
 		return errors.Wrap(err, "tempdir err")
 	}
@@ -168,7 +167,7 @@ func gitclone(url, tempdir string) (string, error) {
 	if err != nil {
 		return "", fmt.Errorf("output: %s", bts.String())
 	}
-	ff, err := ioutil.ReadDir(tempdir)
+	ff, err := os.ReadDir(tempdir)
 	if err != nil {
 		return "", err
 	}
@@ -360,5 +359,5 @@ func rewriteGitIgnore(dir string) error {
 		return errors.Wrap(err, "error while scanning")
 	}
 	f.Close()
-	return ioutil.WriteFile(p, []byte(strings.Join(lines, "\n")+"\n"), 0o666)
+	return os.WriteFile(p, []byte(strings.Join(lines, "\n")+"\n"), 0o666)
 }

mod.go

@@ -1,18 +1,17 @@
 package mod
 
 import (
-	"io/ioutil"
+	"os"
 	"path/filepath"
 
-	// "github.com/marwan-at-work/vgop/modfile"
 	"github.com/pkg/errors"
 	"golang.org/x/mod/modfile"
 )
 
 // GetModFile returns an AST of the given directory's go.mod file
 // and returns err if file is not found.
 func GetModFile(dir string) (*modfile.File, error) {
-	bts, err := ioutil.ReadFile(filepath.Join(dir, "go.mod"))
+	bts, err := os.ReadFile(filepath.Join(dir, "go.mod"))
 	if err != nil {
 		return nil, errors.Wrap(err, "could not open go.mod file")
 	}