less's .lesshst misfeature

[David Holland <dholland%netbsd.org@localhost>]

With the last update to less it (and more along with it) grew a
misfeature where it saves all the patterns you search for within files
to ~/.lesshst for future retrieval.

This is a security/privacy hazard; search strings are expected to be
transient and process-private, and writing them to disk creates the
potential for unwanted disclosures. Writing them to a network-mounted
home directory, meanwhile, can disclose everything the user is doing
to anyone who happens to be listening; this is highly undesirable.

This misfeature can only be disabled by setting an environment
variable, which is a poor method of configuration under the best of
circumstances and fails rather drastically for e.g. running
single-user.

I already patched the code a while back so that attempting to defeat
the feature by e.g. linking /root/.lesshst -> /dev/null no longer
trashes the system.

However, it's been suggested, and several people have concurred, that
it ought to be disabled by default. This is easy to do.

The cost of disabling it by default, however, is that the behavior
diverges from upstream. Are we willing to buy into this? I think we
should, at least for more if not for less.

-- 
David A. Holland
dholland%netbsd.org@localhost