On Thu, Dec 4, 2014 at 1:49 PM, Daniel Kinzler <daniel(a)brightbyte.de> wrote:
This is happening automatically: the SHA1 hash of
every file is computed on
upload, and placed in the img_sha1 field on the database. I believe this
is used
to warn users who try to upload an exact duplicate, but I'm not sure this
is
true.
Indeed; so chances are exact duplicates have been uploaded intentionally.
(It's not certain because they might have been uploaded before this warning
existed, or uploaded by a bot configured to ignore warnings.)
There is also an automated report:
https://commons.wikimedia.org/wiki/Special:ListDuplicatedFiles