archiver: properly create node for vss backups

Previously, NodeFromFileInfo used the original file path to create the
node, which also meant that extended metadata was read from there
instead of within the vss snapshot.

This change is a temporary solution for restic 0.17.2 and will be
replaced with a clean fix in restic 0.18.0.

internal/archiver/archiver.go

@@ -248,7 +248,8 @@ func (arch *Archiver) trackItem(item string, previous, current *restic.Node, s I
 
 // nodeFromFileInfo returns the restic node from an os.FileInfo.
 func (arch *Archiver) nodeFromFileInfo(snPath, filename string, fi os.FileInfo, ignoreXattrListError bool) (*restic.Node, error) {
-	node, err := restic.NodeFromFileInfo(filename, fi, ignoreXattrListError)
+	mappedFilename := arch.FS.MapFilename(filename)
+	node, err := restic.NodeFromFileInfo(mappedFilename, fi, ignoreXattrListError)
 	if !arch.WithAtime {
 		node.AccessTime = node.ModTime
 	}

internal/fs/fs_local.go

@@ -18,6 +18,12 @@ func (fs Local) VolumeName(path string) string {
 	return filepath.VolumeName(path)
 }
 
+// MapFilename is a temporary hack to prepare a filename for usage with
+// NodeFromFileInfo. This is only relevant for LocalVss.
+func (fs Local) MapFilename(filename string) string {
+	return filename
+}
+
 // Open opens a file for reading.
 func (fs Local) Open(name string) (File, error) {
 	f, err := os.Open(fixpath(name))

internal/fs/fs_local_vss.go

@@ -145,6 +145,12 @@ func (fs *LocalVss) Lstat(name string) (os.FileInfo, error) {
 	return os.Lstat(fs.snapshotPath(name))
 }
 
+// MapFilename is a temporary hack to prepare a filename for usage with
+// NodeFromFileInfo. This is only relevant for LocalVss.
+func (fs *LocalVss) MapFilename(filename string) string {
+	return fs.snapshotPath(filename)
+}
+
 // isMountPointIncluded  is true if given mountpoint included by user.
 func (fs *LocalVss) isMountPointIncluded(mountPoint string) bool {
 	if fs.excludeVolumes == nil {

internal/fs/fs_reader.go

@@ -39,6 +39,12 @@ func (fs *Reader) VolumeName(_ string) string {
 	return ""
 }
 
+// MapFilename is a temporary hack to prepare a filename for usage with
+// NodeFromFileInfo. This is only relevant for LocalVss.
+func (fs *Reader) MapFilename(filename string) string {
+	return filename
+}
+
 // Open opens a file for reading.
 func (fs *Reader) Open(name string) (f File, err error) {
 	switch name {

internal/fs/interface.go

@@ -11,6 +11,7 @@ type FS interface {
 	OpenFile(name string, flag int, perm os.FileMode) (File, error)
 	Stat(name string) (os.FileInfo, error)
 	Lstat(name string) (os.FileInfo, error)
+	MapFilename(filename string) string
 
 	Join(elem ...string) string
 	Separator() string