The point was that I mistakenly used a snippet of GPLv3 licensed code (which was explicitly licensed in the snippet), and then mistakenly licensed the whole thi

The point was that I mistakenly used a snippet of GPLv3 licensed code (which was explicitly licensed in the snippet), and then mistakenly licensed the whole thing as public domain. I think it may have been illegal for me to say that it's public domain if I used that snippet. That's why I quickly relicensed. However, git commit history is forever, and one git commit contains the GPL snippet + my public domain declaration.