tailscale: update tailfs file and package names (#11590)

This change updates the tailfs file and package names to their new
naming convention.

Updates #tailscale/corp#16827

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>

drive/driveimpl/shared/stat.go

@@ -0,0 +1,73 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package shared
+
+import (
+	"context"
+	"io/fs"
+	"os"
+	"time"
+
+	"github.com/tailscale/xnet/webdav"
+)
+
+// StaticFileInfo implements a static fs.FileInfo
+type StaticFileInfo struct {
+	// Named controls Name()
+	Named string
+	// Sized controls Size()
+	Sized int64
+	// Moded controls Mode()
+	Moded os.FileMode
+	// BirthedTime controls BirthTime()
+	BirthedTime time.Time
+	// BirthedTimeErr stores any error encountered when trying to get BirthTime
+	BirthedTimeErr error
+	// ModdedTime controls ModTime()
+	ModdedTime time.Time
+	// Dir controls IsDir()
+	Dir bool
+}
+
+// BirthTime implements webdav.BirthTimer
+func (fi *StaticFileInfo) BirthTime(_ context.Context) (time.Time, error) {
+	return fi.BirthedTime, fi.BirthedTimeErr
+}
+func (fi *StaticFileInfo) Name() string       { return fi.Named }
+func (fi *StaticFileInfo) Size() int64        { return fi.Sized }
+func (fi *StaticFileInfo) Mode() os.FileMode  { return fi.Moded }
+func (fi *StaticFileInfo) ModTime() time.Time { return fi.ModdedTime }
+func (fi *StaticFileInfo) IsDir() bool        { return fi.Dir }
+func (fi *StaticFileInfo) Sys() any           { return nil }
+
+func RenamedFileInfo(ctx context.Context, name string, fi fs.FileInfo) *StaticFileInfo {
+	var birthTime time.Time
+	var birthTimeErr error
+	birthTimer, ok := fi.(webdav.BirthTimer)
+	if ok {
+		birthTime, birthTimeErr = birthTimer.BirthTime(ctx)
+	}
+
+	return &StaticFileInfo{
+		Named:          Base(name),
+		Sized:          fi.Size(),
+		Moded:          fi.Mode(),
+		BirthedTime:    birthTime,
+		BirthedTimeErr: birthTimeErr,
+		ModdedTime:     fi.ModTime(),
+		Dir:            fi.IsDir(),
+	}
+}
+
+// ReadOnlyDirInfo returns a static fs.FileInfo for a read-only directory
+func ReadOnlyDirInfo(name string, ts time.Time) *StaticFileInfo {
+	return &StaticFileInfo{
+		Named:       Base(name),
+		Sized:       0,
+		Moded:       0555,
+		BirthedTime: ts,
+		ModdedTime:  ts,
+		Dir:         true,
+	}
+}