bitcoin/bitcoin — pull request #1426 by rebroad (2012-06-05 22:44:37+00:00)
Title: Show more significant bytes of block hashes.

On Mon Aug 16 20:55:54 2010, Satoshi modified the client to display 20 bytes of the block hash (up from 16 bytes). This pull request increases the number of significant bytes by 5, and reduces the number of insignificant bytes (almost always zeros) by 10, resulting in saved space in debug.log and improved uniqueness of block hashes.