fix: simplify set-default remote parsing

Author: majiayu000

pkg/cmd/repo/setdefault/setdefault.go

@@ -92,10 +92,6 @@ func NewCmdSetDefault(f *cmdutil.Factory, runF func(*SetDefaultOptions) error) *
 				var err error
 				opts.Repo, err = ghrepo.FromFullName(args[0])
 				if err != nil {
-					if opts.Remotes == nil {
-						return fmt.Errorf("given arg is not a valid repo or git remote: %w", err)
-					}
-
 					remotes, remoteErr := opts.Remotes()
 					if remoteErr != nil {
 						return remoteErr

pkg/cmd/repo/setdefault/setdefault_test.go

@@ -116,10 +116,17 @@ func TestNewCmdSetDefault(t *testing.T) {
 		io.SetStdoutTTY(true)
 		io.SetStdinTTY(true)
 		io.SetStderrTTY(true)
+		remotesFunc := tt.remotes
+		if remotesFunc == nil {
+			remotesFunc = func() (context.Remotes, error) {
+				return context.Remotes{}, nil
+			}
+		}
+
 		f := &cmdutil.Factory{
 			IOStreams: io,
 			GitClient: &git.Client{GitPath: "/fake/path/to/git"},
-			Remotes:   tt.remotes,
+			Remotes:   remotesFunc,
 		}
 
 		var gotOpts *SetDefaultOptions