The problem of deleting stuff from a history of changes is challenging. But I think Darcs, the distributed version control system written in Haskell, does this

The problem of deleting stuff from a history of changes is challenging. But I think Darcs, the distributed version control system written in Haskell, does this rather neatly. Darcs is different from git in that a "commit" (called a "patch" in Darcs lingo) does not depend upon the entire history of what has come before. Rather it has specified dependencies, which Darcs can infer itself – or you can specify if you want more semantic content in the patch structure. A repository is a collection of patches, which are merged using something called patch algebra. So, if you want to delete a patch, you just issue the command "darcs obliterate" and it will remove the patch, and anything which depends on it. Then working directory is reconstructed by merging together any loose ends using patch algebra. With careful administration of dependencies, this approach makes deleting specific things very slick.