StatictakeCopies the current credentials aside. Only ENOENT means there is
nothing to copy: a symlink, a directory or an unreadable file there is
not "nothing", and the save must stop rather than replace it.
Filesystem the credentials live on.
Absolute path to credentials.json.
The backup, or why the save must not go ahead.
Puts the credentials back as they were before the save: the copy is renamed over them, or on a first save the new file is removed. A copy that cannot be put back is kept, because it is the only one left.
What stopped the save.
The failure, naming the restore's own failure when there is one.
Deletes the copy once it is no longer needed, best-effort: a copy left behind is swept like any staged file.
Whether no copy is left.
The credentials as they stood before a save, and how to put them back.