Bug#339978: marked as done (ssh: upgrades from sarge stop due to conffile changes)
You have to use sarge dpkg while updating ssh, since the etch dpkg
suffixes the conffile fields with " obsolete" when they're no longer owned
by a package. Then, packages including that pathname automatically take
over the files. But, I don't know if anything guarantees that etch dpkg
will be both installed and re-execed by apt before updating ssh, so IMO
packages should upgrade silently WRT conffiles from sarge to etch. Etch+1
will need much less conffile foo, for for this situation.