What's in an exit code?

Can you trust the meaning of an exit code from an app of which you have no specific knowledge? I wouldn’t recommend it. But what James and I are wondering is, can you at least trust an application to only return zero if nothing bad happened? Version Control lets users configure their own tools to compare and content-merge files, and we’re discussing a finer point in how we interact with such tools (including the one we ship with out of the box). Check it out and let him (us) know what you think.