Make duplicate output paths an error instead of a warning

[matts1]

pkg_tar can detect when there are file conflicts (code). However, when it detects them, it prints them instead of failing. I see no reason why anyone would want it on print other than for backwards compatibility (which I assume is why it was first added), but if anyone can think of a reason, please tell me.

I'm happy to implement this myself. However, there are a few ways we could do it, and I don't know what the best approach would be to take. I was looking for approval / feedback on the best approach to take.

Option 1: Simple cutoff
Change print to fail, and maybe increment the major version to indicate backwards incompatible changes. Alternatively, we may consider waiting for a major version increase to do this.

Option 2: Feature flag
Create a bool_flag that controls whether it prints or fails. Initially default it to false, and when we release other backwards incompatible changes, we can set it to true.

[aiuto]

Agreed. It should fail, and it only prints a warning for backwards compatibility with bad use cases. I am happy to go with option 2, but with a rule attribute rather than fail as the default.
allow_duplicates_with_different_content=False. That name nicely hints that you are asking for something bad if you set it true. On fail, the messages can say what attribute to add.

I think the backwards compatibility problem is not as bad as it could be. There are a lot of dups, but for the same source file. Few people are doing sophisticated attribute rewrites and also having dups. If a large organization really needs a global default change, they can vendor in the rules and fix it there.

We'll do the next release as 0.9.0.