Don't set username on Windows

Lookup up the username involves a slow AD query. Just skip setting it; the only
effect is to create logfiles with the name unknownuser in the path.

cl/267237763 (google-internal)

glog_file.go

@@ -26,7 +26,6 @@ import (
 	"fmt"
 	"io"
 	"os"
-	"os/user"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -68,9 +67,8 @@ func init() {
 		host = shortHostname(h)
 	}
 
-	current, err := user.Current()
-	if err == nil {
-		userName = current.Username
+	if u := lookupUser(); u != "" {
+		userName = u
 	}
 	// Sanitize userName since it is used to construct file paths.
 	userName = strings.Map(func(r rune) rune {

glog_file_nonwindows.go

@@ -0,0 +1,28 @@
+// Go support for leveled logs, analogous to https://github.com/google/glog.
+//
+// Copyright 2024 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !windows
+
+package glog
+
+import "os/user"
+
+func lookupUser() string {
+	if current, err := user.Current(); err == nil {
+		return current.Username
+	}
+	return ""
+}

glog_file_windows.go

@@ -0,0 +1,33 @@
+// Go support for leveled logs, analogous to https://github.com/google/glog.
+//
+// Copyright 2024 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build windows
+
+package glog
+
+import (
+	"os"
+)
+
+func lookupUser() string {
+	if u := os.Getenv("USER"); u != "" {
+		return u
+	}
+	if u := os.Getenv("USERNAME"); u != "" {
+		return u
+	}
+	return ""
+}