Move gitlab-shell to make Go development easier

For Go development we want to have a GOPATH directory layout for gitlab-shell.

Because this is confusing and distracting for Ruby developers, this change puts the GOPATH at /go-gitlab-shell, and makes /gitlab-shell a symlink to the real directory where the gitlab-shell repository is.

Discussion about Go in gitlab-shell: https://gitlab.com/gitlab-org/gitlab-shell/issues/80

Gitlab-shell Go merge request: https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/127

support/symlink-gitlab-shell

+#!/usr/bin/env ruby
+
+require 'fileutils'
+require 'time'
+
+def main(symlink, target)
+  return if File.symlink?(symlink)
+
+  if File.exist?(symlink)
+    # there is an old directory at the symlink location
+    FileUtils.mv(symlink, "#{symlink}.#{Time.now.iso8601}")
+  end
+
+  FileUtils.ln_s(target, symlink)
+end
+
+if ARGV.count != 2
+  abort "Usage: #{$0} SYMLINK TARGET"
+end
+
+main(*ARGV)