Reuben Thomas wrote:
This variable `Info-default-directory-list' is used as the default
for initializing `Info-directory-list' when Info is started, unless
the environment variable INFOPATH is set.
which means that if I set INFOPATH, then I don't get access to Emacs's own
info files (under /usr/share/info/emacs-22) unless I manually add this path
to Info-directory-list.
The doc of Info-directory-list says that if INFOPATH ends in a colon,
INFOPATH is combined with Info-default-directory-list. Works for me.