Support for downloading Julia instead of building from source.

Jenkinsfile

@@ -24,7 +24,7 @@ def get(Map args) {
     } else if (args.scm == "git" || args.scm == null) {
 	rev = args.branch ?: "master"
 	if (rev.startsWith("tag:"))
-	   rev = "refs/tags/" + rev[4..-1]
+	   rev = "refs/tags/" + rev["tag:".length()..-1]
 	checkout([$class: "GitSCM",
 	    userRemoteConfigs: [[url: url]],
 	    branches: [[name: rev]],
@@ -90,8 +90,13 @@ node(label: nodeLabel) {
 	    sh "meta/prepare.rb"
             // Update repositories
             if (rebuild != "none") {
-		get url: "https://github.com/julialang/julia",
-		    branch: julia_version
+		if (julia_version.startsWith("download:")) {
+		    raw_julia_version = julia_version["download:".length()..-1]
+		    sh "meta/download-julia.rb $raw_julia_version"
+		} else {
+		    get url: "https://github.com/julialang/julia",
+			branch: julia_version
+		}
 		get url: "https://github.com/gap-system/gap",
 		    branch: gap_version
 		get url: "https://github.com/Singular/Singular",

download-julia.rb

@@ -0,0 +1,18 @@
+#!/usr/bin/env ruby
+require_relative "settings.rb"
+require_relative "utils.rb"
+
+version = ARGV.first
+major_version = version.split(".")[0..1].join(".")
+url = "https://julialang-s3.julialang.org/bin/linux/x64/#{major_version}/julia-#{version}-linux-x86_64.tar.gz"
+
+
+Dir.chdir($WORKSPACE) do
+  system! "wget", "-q", "-t", "5", "-N", "--no-if-modified-since", url
+  FileUtils.rm_tree "julia"
+  FileUtils.mkdir_p "julia"
+  julia_tar_gz = File.basename(url)
+  Dir.chdir("julia") do
+    system! "tar", "xzf", "../#{julia_tar_gz}", "--strip-components=1"
+  end
+end

install/install-julia.rb

@@ -2,5 +2,7 @@
 require_relative "../settings.rb"
 require "fileutils"
 
-system! "make -C julia -j#{ENV['BUILDJOBS'] || 4}"
-FileUtils.ln_sf "#{$WORKSPACE}/julia/julia", "local/bin" or exit 1
+if not (ENV["JULIA_VERSION"] || "").start_with?("download:") then
+  system! "make -C julia -j#{ENV['BUILDJOBS'] || 4}"
+end
+FileUtils.ln_sf "#{$WORKSPACE}/julia/bin/julia", "local/bin" or exit 1