rg3/youtube-dl — pull request #1562 by phihag (2013-10-06 02:32:21+00:00)
Title: Add basic --download-archive option

Often, users want to be able to download only videos they haven't seen before, despite the video files having been deleted or moved in the mean time.

When `--download-archive FILE` is given, the extractor and ID of every download is recorded in the specified file. If it is already present, the video in question is skipped.