The .in.in file was added to the repo in 8bdfa6a4e56f. Then Gary added the .in file to POTFILES.in in 1d98555... but I think it should actually be the .in.in file, right?
PidginandFinch:ThePimpin' Penguin IM Clients That'reGoodfortheSoul
Thisfileintendstolistallchangestolibpurple,Pidgin,andFinch's public