I was readinghttps://www.debian.org/releases/stable/i386/apbs04.html.en#preseed-partman . In the third paragraph there is a link labeled "debian-installer source repository" pointing to http://anonscm.debian.org/gitweb/?p=d-i/debian-installer.git;a=tree;f=doc/devel .
That gives a 404 error. I believe the link should be https://anonscm.debian.org/cgit/d-i/debian-installer.git/plain/doc/devel/partman-auto-recipe.txt
