mod: wrong require when migrate from dep with source config

This change modifies Go to generate correct go.mod file.
Currently go-mod puts wrong module path in requires when
Gopkg.toml contains source config. for example, there is
a constraint declaration in Gopkg.toml as following:

[[constraint]]
  name = "github.com/minio/minio-go"
  revision = "0415038e6086735b8c917d7fdb2ca93f07d7fb60"
  source = "https://github.com/liuchang0812/minio-go"

go-mod puts `github.com/liuchang0812/minio-go` in requires.
but, it should be `github.com/minio/minio-go`

Signed-off-by: Chang Liu <[email protected]>

src/cmd/go/internal/modconv/convert.go

@@ -91,8 +91,10 @@ func ConvertLegacyConfig(f *modfile.File, file string, data []byte) error {
 			if err != nil {
 				return fmt.Errorf("add replace: %v", err)
 			}
+			f.AddNewRequire(re.Old.Path, need[path], false)
+		} else {
+			f.AddNewRequire(path, need[path], false)
 		}
-		f.AddNewRequire(path, need[path], false)
 	}
 
 	f.Cleanup()