>> And nowhere in the elpa repository do I find some statement that for >> auctex the externals/auctex branch in elpa.git is to be used instead >> of the main or master branch of auctex.git. > It's always built from `externals/<PKG>`.
Well, not for `make auctex.tar` where it's built from whatever is HEAD in `packages/auctex`. But in `elpa.gnu.git` HEAD is indeed pointing to `externals/<PKG>`. Stefan