BUG #4699: pg_restore hangs with incorrect file format

The following bug has been logged online:

Bug reference: 4699
Logged by: Scott Reed
Email address: sreed(at)avacoda(dot)com
PostgreSQL version: 8.3
Operating system: Windows XP
Description: pg_restore hangs with incorrect file format
Details:

"pg_restore <filename>" hangs if the file format is not one of the
non-plain-text formats created by pg_dump. There does not appear to be a log
or error message to explain what is happening. Apparently this also causes
the OK button to be disabled in the pgAdmin Restore dialog, again without
any explanation, even though the file has been created using the pgAdmin
Backup dialog (albeit in plain-text format).

My suggestions for a fix is to have pg_restore return an error if the file
format is incorrect.

Carry over to pgAdmin:
1) in the pgAdmin Backup dialog only display the last file used if 1) the
file name has the default file extension for the selected format or b) the
selected format matches the format used when backing up to the last file.
2) in the pgAdmin Restore dialog display the error message from pg_restore
(see pg_restore suggested fix) when the file format is incorrect to explain
why the OK button is disabled.