But why put that info in commit message instead of a comment in the file itself?
Because that is effort every person who uses the file has to do over and over again, whereas maintaining the file is effort that has to be done once by one person.
https://github.com/eamodio/vscode-gitlens/tree/v11.2.1#curre... (screenshot)
> Current Line Blame: Adds an unobtrusive, customizable, and themable, blame annotation at the end of the current line
git blame -w -M
This will ignore whitespace and detect moved or copied lines.