run go mod tidy over a conflicted go.mod
$ cat go.mod
module github.com/mkmik/gomoerge
go 1.16
<<<<<<< HEAD
require github.com/google/renameio v0.1.0
=======
require github.com/google/renameio v1.0.0
>>>>>>> foobar
$ gomoerge
$ cat go.mod
module github.com/mkmik/gomoerge
go 1.16
require github.com/google/renameio v1.0.0