On July 24, 2020, the complete source code for Pokémon Diamond and Pearl was leaked. The data corresponding to the version control system it used - CVS - was intact, to such an extent that a large number of file versions from commits from March 2006 onward are now available to us.
While no builds were present within the repository, a number of builds can be compiled from a handful of the commits. As such, the true extent to the revision history of the game cannot be captured by a small selection of builds, but they still provide key snapshots of development that can provide useful insights.
This sprite shows the Regigigas placeholder sketch as of June 30th, 2006.