BUG #1580: pg_dumpall aborts when cwd is unreadable

The following bug has been logged online:

Bug reference:      1580
Logged by:          David Elliott
Email address:      elliott@stcnet.com
PostgreSQL version: 8.0.1
Operating system:   Mac OS X 10.3.8
Description:        pg_dumpall aborts when cwd is unreadable
Details:

After setting up a cron job to backup the database nightly I noticed it
wasn't running.  The log contained the following messages:

could not identify current directory: Permission denied
could not identify current directory: Permission denied
could not identify current directory: Permission denied
The program "pg_dump" is needed by pg_dumpall but was not found in the
same directory as "pg_dumpall".
Check your installation.

It can be reproduced quite simply on the command-line.  As root and with
CWD= root's home directory (not readable by anyone but root) do this:
# sudo -u postgres /usr/local/pgsql/bin/pg_dumpall

Changing to a path readable by the postgres user before running the command
fixes the issue.

When an absolute path is given I see no reason to read the current directory
before trying the absolute path.