Merge branch 'ab/doc-hash-brokenness'

Doc updates. * ab/doc-hash-brokenness: doc hash-function-transition: clarify what SHAttered means doc hash-function-transition: clarify how older gits die on NewHash

Junio C Hamano committed Apr 11, 2018 at 13:09 UTC d877975e129e85cde331fc776a2592a6f40f10df

No changes.