Switch to an Ubuntu Vagrant image

The non-contrib Debian one doesn’t come with guest additions, meaning it used rsync instead of Virtualbox shared folders to sync files, meaning edits made in the VM didn’t get propogated back to the host, meaning I got very confused for a while.

Thanks to the parent commit, this shouldn’t be an issue at all: the default user name, which is now “ubuntu” instead of “vagrant” is specified in a lot fewer places, making it much easier to change.

.gitignore

@@ -1,4 +1,4 @@
-*~
 target
-testcases
+
 .vagrant
+ubuntu-xenial-16.04-cloudimg-console.log

Vagrantfile

@@ -1,11 +1,15 @@
-Vagrant.configure("2") do |config|
-    config.vm.provider "virtualbox" do |v|
+Vagrant.configure(2) do |config|
+    config.vm.provider :virtualbox do |v|
+        v.name = 'exa'
         v.memory = 1024
         v.cpus = 1
     end
 
-    config.vm.box = "debian/jessie64"
-    config.vm.hostname = "exa"
+
+    # We use Ubuntu instead of Debian because the image comes with two-way
+    # shared folder support by default.
+    config.vm.box = 'ubuntu/xenial64'
+    config.vm.hostname = 'exa'
 
 
     # Install the dependencies needed for exa to build.