search for: delete_sent_files

...is down in the I/O code, and that code doesn't know about the file list. I decided to make this code call a new function, successful_send(), which is back in sender.c. This function is the one that handles translating the index into a file name and deleting the source file (assuming that the delete_sent_files flag is on, which is currently the only time that MSG_SUCCESS gets sent). I also added a run-time flag to mark the items we sent off to the receiver, just to make sure that nothing funny is going on in the sequence of events (aside: the sender side has no copy-on-write issues to make us avoid twea...