Merge Linuxbrew/brew into Homebrew/brew

[sjackman]

We aim to merge Linuxbrew/brew into Homebrew/brew by the end of 2018. Linux users will use Homebrew/brew. Linuxbrew/brew will remain as a fork to be used for development.

• Submit relocatable kegs (keg_relocate.rb) to Homebrew/brew
  • Submit patchelf to Homebrew/core Relocate bottles on Linux using patchelf Homebrew/brew#4382
• Submit Superenv (extend/ENV/super.rb) to Homebrew/brew Add superenv for Linux Homebrew/brew#4185
• Ensure Homebrew/brew on Linux can brew readall Homebrew/homebrew-core and/or Linuxbrew/homebrew-core (probably both)
  • Figure out a solution for MacOS.version
• Submit remaining patches to Homebrew/brew or revert in Linuxbrew/brew (to be determined)
  See Merge Linuxbrew/brew into Homebrew/brew #612 (comment)
• Merge Linuxbrew/homebrew-test-bot into Homebrew/homebrew-test-bot
• Document what Linux platforms Homebrew/brew officially supports
• Document Linux behaviour in documentation (manpage)

This list is not comprehensive and will be expanded as items arise.

Once these tasks are complete, we'll migrate from Linuxbrew/brew to Homebrew/brew in this order:

1. Move Linuxbrew CI to using Homebrew/brew
2. Move Linuxbrew master branch users to using Homebrew/brew's master branch
3. Move Linuxbrew stable/tag users to using Homebrew/brew's master branch

[MikeMcQuaid]

Suggestion for ordering this migration:

1. Move Linuxbrew CI to using Homebrew/brew
2. Move Linuxbrew master branch users to using Homebrew/brew's master branch
3. Move Linuxbrew stable/tag users to using Homebrew/brew's master branch

Additional tasks:

• Document what Linux platforms Homebrew/brew officially supports (likely a single distro and a lower level than Linuxbrew/brew). Instead or as well: consider what the bug reporting/fixing flow is going to look like
• Document Linux behaviour in documentation e.g. manpage
• Figure out a solution for MacOS.version
• Ensure Homebrew/brew on Linux can brew readall Homebrew/homebrew-core and/or Linuxbrew/homebrew-core (probably both)

[sjackman]

These all look good. I've added them to the tracking issue above.

Document what Linux platforms Homebrew/brew officially supports (likely a single distro and a lower level than Linuxbrew/brew)

Linuxbrew builds its bottles on the most recent Ubuntu LTS platform, which is currently Ubuntu 16.04 LTS (Xenial Xerus) and in April will become Ubuntu 18.04 LTS (Bionic Beaver). Other distributions that I'd like to support are Debian, Fedora, and CentOS. The popularity of distribution and version being run on Google Analytics in the last 30 days, in order of popularity, are Ubuntu 16.04, Ubuntu 17.10, Fedora Core 27, Debian 8, Ubuntu 14.04, Ubuntu 12.04, CentOS 7, and Debian 9.

Rank	Distribution	Total Events	Unique Events
1.	Ubuntu 16.04.3 LTS	10,034(19.35%)	9,702(19.77%)
2.	Ubuntu 16.04.3 LTS, custom-prefix	7,264(14.01%)	6,959(14.18%)
3.	Ubuntu 17.10	5,833(11.25%)	5,595(11.40%)
4.	4.13.9-300.fc27.x86_64	1,397(2.69%)	1,305(2.66%)
5.	Debian GNU/Linux 8.10 (jessie), custom-prefix	1,030(1.99%)	887(1.81%)
6.	Ubuntu 14.04.5 LTS	843(1.63%)	812(1.65%)
7.	4.4.0-111-generic, CI	823(1.59%)	823(1.68%)
8.	Ubuntu 16.04.2 LTS	767(1.48%)	738(1.50%)
9.	"CentOS Linux release 7.4.1708 (Core) "	745(1.44%)	728(1.48%)
10.	Debian GNU/Linux 9.3 (stretch)	690(1.33%)	672(1.37%)

[sjackman]

• Figure out a solution for MacOS.version
• Ensure Homebrew/brew on Linux can brew readall Homebrew/homebrew-core and/or Linuxbrew/homebrew-core (probably both)

Current Homebrew/brew on Linux cannot tap Homebrew/core due to…

undefined method `full_version' for OS::Mac:Module
undefined method `version' for OS::Mac::Xcode:Module
undefined method `version' for OS::Mac:Module

@MikeMcQuaid How do you feel about defining these three methods as Version::NULL on Linux?

[MikeMcQuaid]

@MikeMcQuaid How do you feel about defining these three methods as Version::NULL on Linux?

@sjackman That seems reasonable 👍 .

Linuxbrew builds its bottles on the most recent Ubuntu LTS platform, which is currently Ubuntu 16.04 LTS (Xenial Xerus) and in April will become Ubuntu 18.04 LTS (Bionic Beaver).

Cool. I think we should stick with the latest Ubuntu LTS and ensure that our Linux brew tests job is running there, if possible.

[sjackman]

Cool. I think we should stick with the latest Ubuntu LTS and ensure that our Linux brew tests job is running there, if possible.

Use Docker on TravisCI? I haven't used it yet, but seems supported (https://docs.travis-ci.com/user/docker/). Docker support on CircleCI 2.0 is first class.

[sjackman]

@MikeMcQuaid How do you feel about defining these three methods as Version::NULL on Linux?

@sjackman That seems reasonable 👍 .

I've submitted PR Homebrew/brew#3820. There's also MacOS.prefer_64_bit?. That's the last one. Shall I rename this method to OS.prefer_64_bit? and submit PRs to Homebrew/brew and Homebrew/homebrew-core? I'll keep the old name as a deprecated alias.

[MikeMcQuaid]

I've submitted PR Homebrew/brew#3820. There's also MacOS.prefer_64_bit?. That's the last one. Shall I rename this method to OS.prefer_64_bit? and submit PRs to Homebrew/brew and Homebrew/homebrew-core? I'll keep the old name as a deprecated alias.

prefer_64_bit? has always felt a bit weird as a name to me. What about just OS.64_bit? or OS.is_64_bit? CC @ilovezfs in case you have other good naming thoughts.

Use Docker on TravisCI? I haven't used it yet, but seems supported (https://docs.travis-ci.com/user/docker/). Docker support on CircleCI 2.0 is first class.

What's the distro that the base Travis CI image is running?

[ilovezfs]

I guess OS.64_bit? seems fine. Apple is dropping 32-bit support altogether so we may also want a OS.64_bit_only? if that helps inform your naming thoughts at all.

[sjackman]

I liked OS.64_bit?

What's the distro that the base Travis CI image is running?

Ubuntu 12.04 LTS (Trusty Tahr), which is six years old now.

[ilovezfs]

I'm confused. https://docs.travis-ci.com/user/reference/overview/

Sudo-enabled #

A sudo enabled, full virtual machine per build, that runs Linux, either Ubuntu Precise 12.04 or Ubuntu Trusty 14.04.
Container-based #

A fast boot time environment in which sudo commands are not available. Running Linux Ubuntu Trusty 14.04

[sjackman]

You're right. I had forgotten that TravisCI offers both Precise and Trusty. Ubuntu 14.04 LTS (Trusty Tahr) is four years old. TravisCI does not offer the current Ubuntu 16.04 LTS (Xenial Xerus). Ubuntu 18.04 LTS (Bionic Beaver) will be released in April.

[sjackman]

Here's the list of essential (required) Debian packages. It's pretty safe to assume that these packages will be available on most Linux systems.
See https://www.reddit.com/r/debian/comments/6lnakq/what_are_the_essential_packages/

base-files              libattr1                libuuid1
base-passwd             libblkid1               login
bash                    libc-bin                lsb-base
bsdutils                libc6                   mawk
coreutils               libcomerr2              mount
dash                    libfdisk1               multiarch-support
debconf                 libgcc1                 ncurses-base
debianutils             liblzma5                ncurses-bin
diffutils               libmount1               passwd
dpkg                    libpam-modules          perl-base
e2fslibs                libpam-modules-bin      sed
e2fsprogs               libpam-runtime          sensible-utils
findutils               libpam0g                sysvinit-utils
gcc-6-base              libpcre3                tar
grep                    libselinux1             tzdata
gzip                    libsepol1               util-linux
hostname                libsmartcols1           zlib1g
init-system-helpers     libss2
libacl1                 libtinfo5