https://github.com/mikf/gallery-dl/issues/6582#issuecomment-2973285775
To stop gracefully after the current file finishes processing when
Ctrl+C was pressed, or after the current post finishes processing when
SIGUSR1 was received:
{
"signals-actions": {
"SIGINT" : "file",
"SIGUSR1": "post"
}
}