archiver: improve error message for irregular files

Since Go 1.21, most reparse points are considered as irregular files.
Depending on the underlying driver these can exhibit nearly arbitrary
behavior. When encountering such a file, restic returned an
indecipherable error message: `error: invalid node type ""`.

Add the filepath to the error message and state that the file type is
not supported.

internal/archiver/archiver.go

@@ -2,6 +2,7 @@ package archiver
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"path"
 	"runtime"
@@ -183,7 +184,10 @@ func (arch *Archiver) nodeFromFileInfo(snPath, filename string, fi os.FileInfo)
 	}
 	// overwrite name to match that within the snapshot
 	node.Name = path.Base(snPath)
-	return node, errors.WithStack(err)
+	if err != nil {
+		return node, fmt.Errorf("nodeFromFileInfo %v: %w", filename, err)
+	}
+	return node, err
 }
 
 // loadSubtree tries to load the subtree referenced by node. In case of an error, nil is returned.