There is some speculation on whether Linus got it right or wrong, but I haven't seen anyone actually test this with the shattered-1 & 2 files, so I did.

Git sees them as different despite them having the same hash. You can test with:

  mkdir shattered && cd shattered
  git init
  wget https://shattered.it/static/shattered-1.pdf
  git add shattered-1.pdf
  git commit -am "First shattered pdf"
  git status
  wget https://shattered.it/static/shattered-2.pdf
  sha1sum *
  md5sum *
  mv shattered-2.pdf shattered-1.pdf
  git status

So it doesn't see the files the same.

Apologies for those on mobile (please fix this HN!): the commands are: mkdir shattered && cd shattered && git init && wget https://shattered.it/static/shattered-1.pdf && git add shattered-1.pdf && git commit -am "First shattered pdf" && git status && wget https://shattered.it/static/shattered-2.pdf && sha1sum * && md5sum * && mv shattered-2.pdf shattered-1.pdf && git status

EDIT: Ah, of course! git adds a header and takes the sha1sum of the header+content, which breaks the identical SHA1 trick. You can add a footer on and they keep the same SHA1 though. Don't have time to play about with this more just now, but try it with `cat`ing some identical headers and footers onto the pdfs.

EDIT2: Actually, this is discussed more extensively in the other thread which I hadn't read yet. Go there for more details: https://news.ycombinator.com/item?id=13713480