Fix compatibilities with unix >=2.8 package

[a5ob7r]

Since version 2.8, the unix package changed UserEntry and GroupEntry into the ByteString based implementation instead of String as a breaking change. We can compile this package with unix >=2.8 if just re-exports the two of new data types, but it's probably uncomfortable for users because types of fields of the two isn't the same between prior 2.8 and since 2.8. So we need to define and export compatible data types for UserEntry and GroupEntry to resolve this problem.

This patch provides API compatibilities not between platforms but between versions of library, so the compat which this patch provide isn't probably the same as the compat which this package provides.

Fix #57.

[mmhat]

Just got hit by that myself. Thank you for fixing that! 👍

[mmhat]

Maybe just use MIN_VERSION_unix(2, 8, 0) here?

[a5ob7r]

Thank you for your review. I didn't know the MIN_VERSION_* macro. It seems that It's used at other points in this package. I'll use it. No need to use an extra flag if use it.

[mmhat]

What is the reasoning behind introducing an extra flag?

[mitchellwrosen]

Friendly bump.

Btw, another option to work around this incompatibility, @a5ob7r, is to release a new version of unix-compat that only supports unix ^>= 2.8. Users who need an older version of unix can simply use older versions of unix-compat, too.

[mitchellwrosen]

I think the right fix for this is to just delete System.PosixCompat.User. It doesn't contain any helpful cross-platform functionality. I've opened that PR here: #62

[mitchellwrosen]

Thanks for the PR, but we've deleted System.PosixCompat.User entirely, so it's no longer needed. You can find the new repository here https://github.com/haskell-pkg-janitors/unix-compat