EMBEDDED SCM-like ideas sought

Assume a freely distributable C/c++ multithreaded, multiuser product with an embedded database.

One criteria is to be able to compare the state of a record over time - to display what a record looked like, to compare a record's state between various points of its history - an audit trail. A bonus would be a nearly transparent change merging facility if two people happened to be modifiing different parts of the same record at the same time, with some sort of alert/resolution mechanism for changing the same field at the same time.

It feels like to me a reinvention of standard source code management version control algorithms. Are there any freely distributable libraries where much of this is already available? Trying to harvest code from RCS/CVS seems less than optimal. What about user interfaces to the history seems tricky - what interface to a history like this have you seen ''work''?

-- 
"I know of vanishingly few people ... who choose to use ksh." "I'm a minority!"
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