It isn’t the responsibility of the commit command to decide how to treat whitespaces, but the responsibility of the blame command because it is blame which analyzes the differences between versions to get the author of each line. So searching for an option to ignore whitespace in blame:
The option -w is defined as:
“Ignore whitespace when comparing the parent’s version and the child’s to find where the lines came from.”
http://kernel.org/pub/software/scm/git/docs/git-blame.html