R devel - Jan 2015 - How do I prevent '.install_extras' from being installed?

So now I have:
 
vignettes/.install_extras:

inst/doc/figs.*[.]Rnw$


.Rinstignore:

[.]DS_Store
inst/doc/.*[.]pdf$
inst/doc/Sweavel.sty$
inst/doc/[.]install_extras$


Everything is fine except that 'R CMD check ?? generates the note:

"Found the following hidden files and directories:
  inst/doc/.install_extras
These were most likely included in error. See section ?Package
structure? in the ?Writing R Extensions? manual."

John Maindonald             email: john.maindonald at anu.edu.au
phone : +61 2 (6125)3473    fax  : +61 2(6125)5549
Centre for Mathematics & Its Applications, Room 1194,
John Dedman Mathematical Sciences Building (Building 27)
Australian National University, Canberra ACT 0200.