What to do when the target already holds data. 'skip' (the default) leaves it alone, 'overwrite' replaces it, or decide per target with a callback returning true to overwrite.
'skip'
'overwrite'
true
What to do when the target already holds data.
'skip'(the default) leaves it alone,'overwrite'replaces it, or decide per target with a callback returningtrueto overwrite.