Release v6.0.0 (#4002)

* Update all submodules

* Ensure always using lastest docker image

* Allow passing in GEM_VERSION from env

This is useful to building test gems in a cache friendly way using:
`GEM_VERSION=$(git describe --tags 2>/dev/null | sed 's/-/./g' | sed
's/v//') bundle exec rake build_gem`

* Update submodules one last time

* Set version 6.0.0

github-linguist.gemspec

@@ -2,7 +2,7 @@ require File.expand_path('../lib/linguist/version', __FILE__)
 
 Gem::Specification.new do |s|
   s.name    = 'github-linguist'
-  s.version = Linguist::VERSION
+  s.version = ENV['GEM_VERSION'] || Linguist::VERSION
   s.summary = "GitHub Language detection"
   s.description = 'We use this library at GitHub to detect blob languages, highlight code, ignore binary files, suppress generated files in diffs, and generate language breakdown graphs.'
 

lib/linguist/version.rb

@@ -1,3 +1,3 @@
 module Linguist
-  VERSION = "5.3.3"
+  VERSION = "6.0.0"
 end

script/grammar-compiler

@@ -6,6 +6,8 @@ cd "$(dirname "$0")/.."
 image="linguist/grammar-compiler:latest"
 mkdir -p grammars
 
+docker pull $image
+
 exec docker run --rm \
     -u $(id -u $USER):$(id -g $USER) \
     -v $PWD:/src/linguist \