Treat tab as eight characters in grep regex

To count lines wider than 80 columns I currently use this:

$ git grep -c -v '^.{,80}$' **/*.{c,h,p{l,y}} 
    |cut -d ':' -f 2 
    |awk 'BEGIN { i=0 } { i+=$1 } END { printf ("%dn", i) }'

Unfortunately, the repo uses tabs for indenting so the grep pattern
is inaccurate. Is there a way to have the regex treat tabs at the
standard width of 8 chars like wc -L does?

For performance reasons I’d prefer a solution that works inside
git-grep(1) or maybe another grep tool without preprocessing

All topic