DDL diff utility?

My company offers an ASP service for advertising companies using PG.
For contractual reasons, each client gets its own replicated database.
This presents a problem whenever a new feature/fix requires a DDL change
which must be rolled out across N databases. Currently, we keep track of
these changes via a central text file in CVS with manually entered DDL
updates. The problem is making sure that overworked developers actually
log all these changes.

What would be better is a DDL 'diff' utility that would look at a master
and target database and generate the necessary ALTER statements needed
to make the target db look like the master.

Is anyone aware of such a tool for PG? I've only found it for MSSQL.

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Steve Manes http://www.magpie.com
Brooklyn, NY