Prefer $HOME when looking up the current user's home directory.

Prefer $HOME when looking up the current user's home directory.

When we need to identify the home directory on non-Windows, first
consult getenv("HOME").  If that's empty or unset, fall back
on our previous method of checking the <pwd.h> database.

Preferring $HOME allows the user to intentionally point at some
other directory, and it seems to be in line with the behavior of
most other utilities.  However, we shouldn't rely on it completely,
as $HOME is likely to be unset when running as a daemon.

Anders Kaseorg

Discussion: https://postgr.es/m/1634252654444.90107@mit.edu