Make sure the hash is pre-package unique, fixes #2857.
Make sure the hash is pre-package unique, fixes #2857.

Signed-off-by: Edward Z. Yang <dbd597f5635f432486c5d365e9bb585b3eaa1853@cs.stanford.edu>

lukexi/cabal,thomie/cabal,thoughtpolice/cabal,thomie/cabal,themoritz/cabal,randen/cabal,kolmodin/cabal,trskop/cabal,enolan/cabal,gbaz/cabal,kolmodin/cabal,Peaker/cabal,thoughtpolice/cabal,bennofs/cabal,lukexi/cabal,Heather/cabal,sopvop/cabal,martinvlk/cabal,garetxe/cabal,sopvop/cabal,mmakowski/cabal,trskop/cabal,headprogrammingczar/cabal,headprogrammingczar/cabal,bennofs/cabal,Peaker/cabal,randen/cabal,martinvlk/cabal,mydaum/cabal,edsko/cabal,enolan/cabal,mmakowski/cabal,garetxe/cabal,themoritz/cabal,gbaz/cabal,mydaum/cabal,themoritz/cabal,edsko/cabal,sopvop/cabal,Heather/cabal