mirror: add command to mirror to Bintray. (#263)

Used for uploading imagemagick 6.9.4-3.

Library/Homebrew/dev-cmd/mirror.rb

+# Mirrors the stable URL for a formula on Bintray.
+#
+# Usage: brew mirror <formula> [<formula> ...]
+
+module Homebrew
+  def mirror
+    if ARGV.named.empty?
+      odie "This command requires at least formula argument!"
+    end
+
+    bintray_user = ENV["BINTRAY_USER"]
+    bintray_key = ENV["BINTRAY_KEY"]
+    if !bintray_user || !bintray_key
+      raise "Missing BINTRAY_USER or BINTRAY_KEY variables!"
+    end
+
+    ARGV.formulae.each do |f|
+      bintray_package = Utils::Bottles::Bintray.package f.name
+      bintray_repo_url = "https://api.bintray.com/packages/homebrew/mirror"
+      package_url = "#{bintray_repo_url}/#{bintray_package}"
+
+      unless system "curl", "--silent", "--fail", "--output", "/dev/null", package_url
+        package_blob = <<-EOS.undent
+          {"name": "#{bintray_package}",
+           "public_download_numbers": true,
+           "public_stats": true}
+        EOS
+        curl "--silent", "--fail", "-u#{bintray_user}:#{bintray_key}",
+             "-H", "Content-Type: application/json",
+             "-d", package_blob, bintray_repo_url
+        puts
+      end
+
+      download = f.fetch
+      f.verify_download_integrity(download)
+      filename = download.basename
+      destination_url = "https://dl.bintray.com/homebrew/mirror/#{filename}"
+
+      ohai "Uploading to #{destination_url}"
+      content_url = "https://api.bintray.com/content/homebrew/mirror"
+      content_url += "/#{bintray_package}/#{f.pkg_version}/#{filename}"
+      content_url += "?publish=1"
+      curl "--silent", "--fail", "-u#{bintray_user}:#{bintray_key}",
+           "-T", download, content_url
+      puts
+      ohai "Mirrored #{filename}!"
+    end
+  end
+end