Use BSD tar's libarchive LZMA support if available

[MikeMcQuaid]

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---

Avoid using an unnecessary xz dependency when it's not needed.

This may well require some refactoring and I need to confirm that these macOS versions are correct. Thanks to @zmwangx for pointing out that this was possible; I had no idea.

[zmwangx]

Do the "older versions of tar" that "require an explicit format flag" happen to be tar on 10.6 or lower? In any case, even if it's unnecessary, IMO it would be better to add a clause for :xz:

elsif type == :xz
  tar_flags << "J"
end

which is arguably safer (no one needs to ask the older versions question I raised above), and at least feels more complete.

[MikeMcQuaid]

They could be, I'll double-check. Couldn't find the J in the manpage.

[scpeters]

Yeah, I don't see it in the manpage either, but it is in the --help string:

$ tar --help | grep '\-J'
  -z, -j, -J, --lzma  Compress archive with gzip/bzip2/xz/lzma

[zmwangx]

What about /usr/bin/tar? (xar path is hard-coded too.)

tar in pipe_to_tar (below, outside the current set of diffs) should be hard-coded too.

[chdiza]

It should definitely be /usr/bin/tar. We had a bug or two a while back when there were plain tar invocations.

[MikeMcQuaid]

This is to make Linuxbrew's life a bit easier. We haven't seen any bugs with this for a long time. Once we have environment sanitisation we can hopefully start to filter a lot more PATHs out.

[zmwangx]

Care to list a Linux distro without a full blown /usr/bin/tar (other than embedded distros, e.g. busybox based ones liks OpenWrt)?

[MikeMcQuaid]

You're proposing making a change to additional code so the onus is not on me to research why I shouldn't change the existing code. It's not a bug we're seeing and I don't think speculative fixing like that is a sensible approach as it may break things for forks like Linuxbrew and it's not gaining us anything today. Again, happy to have a longer-term PATH-filtering solution that addresses all these cases and avoids us having to hard-code anything.

[MikeMcQuaid]

This may well require some refactoring and I need to confirm that these macOS versions are correct.

Refactored so this works properly on non-macOS and confirmed that Lion was indeed the first version to support this. This adds additional weight to using xz bottles.

[ilovezfs]

Um

==> Verifying wget-1.18.tar.xz checksum
tar xJf /Users/joe/Library/Caches/Homebrew/wget-1.18.tar.xz
tar: Error opening archive: Child process exited with status 254Child process exited with status 254
Error: Failure while executing: tar xJf /Users/joe/Library/Caches/Homebrew/wget-1.18.tar.xz
/usr/local/Homebrew/Library/Homebrew/utils.rb:276:in `safe_system'
/usr/local/Homebrew/Library/Homebrew/download_strategy.rb:79:in `safe_system'
/usr/local/Homebrew/Library/Homebrew/download_strategy.rb:247:in `block in stage'
/usr/local/Homebrew/Library/Homebrew/utils.rb:254:in `with_system_path'
/usr/local/Homebrew/Library/Homebrew/download_strategy.rb:243:in `stage'
/usr/local/Homebrew/Library/Homebrew/resource.rb:95:in `block in unpack'
/usr/local/Homebrew/Library/Homebrew/extend/fileutils.rb:14:in `block in mktemp'
/usr/local/Homebrew/Library/Homebrew/extend/fileutils.rb:74:in `block in run'
/usr/local/Homebrew/Library/Homebrew/extend/fileutils.rb:74:in `chdir'
/usr/local/Homebrew/Library/Homebrew/extend/fileutils.rb:74:in `run'
/usr/local/Homebrew/Library/Homebrew/extend/fileutils.rb:13:in `mktemp'
/usr/local/Homebrew/Library/Homebrew/resource.rb:94:in `unpack'
/usr/local/Homebrew/Library/Homebrew/resource.rb:86:in `stage'
/usr/local/Homebrew/Library/Homebrew/formula.rb:1799:in `stage'
/usr/local/Homebrew/Library/Homebrew/formula.rb:1075:in `brew'
/usr/local/Homebrew/Library/Homebrew/build.rb:112:in `install'
/usr/local/Homebrew/Library/Homebrew/build.rb:187:in `<main>'

[ilovezfs]

💣 #1299.