Merge pull request Homebrew#3182 from ilovezfs/ac_cv_xcode9

superenv: help Autotools with 10.13 SDK on 10.12

Merge pull request Homebrew#3076 from DomT4/high_sierra_b7

mac/xcode: update expected Clang on 10.13

formula_cellar_checks: remove stray backtick.

Merge pull request Homebrew#2978 from reitermarkus/simplify-dsl

Simplify `assert_only_one_stanza_allowed`.

Merge pull request Homebrew#2954 from ilovezfs/allow-install-mixed-bu…

…ild-dependency-tree

formula_installer: allow version mismatched build deps

Merge pull request Homebrew#2931 from JCount/version-devel-parsing-im…

…provements

version: improve devel spec version parsing

Merge pull request Homebrew#2851 from MikeMcQuaid/missing-formula-no-…

…core

missing_formula: no need to tap homebrew/core.

Merge pull request Homebrew#2769 from MikeMcQuaid/rubocop-no-perl-bac…

…krefs

rubocop: don’t allow Perl regex backrefs.

Merge pull request Homebrew#2599 from peternewman/patch-1

Fix internal links on the manpage

Merge pull request Homebrew#2631 from GauthamGoli/audit_homepage_rubocop

audit: Port audit_homepage method to rubocop and add tests