View Source ExTDLib.Object.MessageCopyOptions (ExTDLib v0.0.4)

Options to be used when a message content is copied without reference to the original sender. Service messages, and messages with messageInvoice or messagePremiumGiveaway content can't be copied.

NameTypeDescription
send_copyboolTrue, if content of the message needs to be copied without reference to the original sender. Always true if the message is forwarded to a secret chat or is local.
replace_captionboolTrue, if media caption of the message copy needs to be replaced. Ignored if send_copy is false.
new_captionformattedTextNew message caption; pass null to copy message without caption. Ignored if replace_caption is false.

More details on telegram's documentation.