feat: Implement tarball caching

.gitignore

@@ -24,3 +24,5 @@ mash-*.tar
 
 # Temporary files, for example, from tests.
 /tmp/
+
+.mash-cache.tar.gz

.gitlab-ci.yml

@@ -1,5 +1,8 @@
 test:
   image: "elixir:1.14.4"
+  cache:
+    paths:
+    - .mash-cache.tar.gz
   script:
     - mix local.hex --force
     - mix local.rebar --force

.mash.exs

@@ -5,11 +5,25 @@ defmodule MashConfig do
 
   def jobs do
     [
+      %{
+        name: :restore_cache,
+        run: restore_cache()
+      },
       %{
         name: :test,
+        needs: [:restore_cache],
         run: mix("test")
       },
-      %{name: :credo, run: mix("credo", ["--all"])},
+      %{
+        name: :credo,
+        needs: [:restore_cache],
+        run: mix("credo", ["--all"])
+      },
+      %{
+        name: :save_cache,
+        needs: [:test],
+        run: save_cache()
+      }
     ]
   end
 end

lib/mash/helpers.ex

@@ -17,6 +17,30 @@ defmodule Mash.Helpers do
     end
   end
 
+  def save_cache(name \\ ".mash-cache", files \\ ["deps", "_build"]) do
+    fn io_pid ->
+      cmd("tar", ["-czpf", "#{name}.tar.gz" | files], io_pid)
+    end
+  end
+
+  def restore_cache(name \\ ".mash-cache") do
+    fn io_pid ->
+      Process.group_leader(self(), io_pid)
+
+      path = "#{name}.tar.gz"
+
+      if File.exists?(path) do
+        cmd("tar", ["-xzf", "#{name}.tar.gz", "--atime-preserve"], io_pid)
+      else
+        IO.puts(
+          IO.ANSI.yellow() <> "Warning: cache file #{path} does not exist." <> IO.ANSI.reset()
+        )
+
+        {[], 0}
+      end
+    end
+  end
+
   def fun(fun) do
     fn io_pid ->
       Process.group_leader(self(), io_pid)