Wrote some evil code you don't want to run today. Git.Destroyer randomly generates Damage, and applies it to a git repository, in a way that is reproducible -- applying the same Damage to clones of the same git repo will always yeild the same result.

This let me build a test harness for git-repair, which repeatedly clones, damages, and repairs a repository. And when it fails, I can just ask it to retry after fixing the bug and it'll re-run every attempt it's logged.

This is already yeilding improvements to the git-repair code. The first randomly constructed Damage that it failed to recover turned out to be a truncated index file that hid some other corrupted object files from being repaired.

[Damage Empty (FileSelector 1),
 Damage Empty (FileSelector 2),
 Damage Empty (FileSelector 3),
 Damage Reverse (FileSelector 3),
 Damage (ScrambleFileMode 3) (FileSelector 5),
 Damage Delete (FileSelector 9),
 Damage (PrependGarbage "¥SOH¥STX¥ENQ¥f¥a¥ACK¥b¥DLE¥n") (FileSelector 9),
 Damage Empty (FileSelector 12),
 Damage (CorruptByte 11 25) (FileSelector 6),
 Damage Empty (FileSelector 5),
 Damage (ScrambleFileMode 4294967281) (FileSelector 14)

I need to improve the ranges of files that it damages -- currently QuickCheck seems to only be selecting one of the first 20 or so files. Also, it's quite common that it will damage .git/config so badly that git thinks it's not a git repository anymore. I am not sure if that is something git-repair should try to deal with.

Today's work was sponsored by the WikiMedia Foundation.