Finds duplicate files based on SHA-1 hash of file contents.
##Options
-r: recurses on subdirectories
-D: removes duplicates by preserving the first file and deleting all others that share the same sha1_id.
<index>:<sha1_id>:<path>
index: human-readable, numeric index
sha1_id: first 4-bytes of the SHA-1 hash
path: path of the duplicate