repo: init

Generate repo with

mix new aoc2025

I'm recreating the scaffolding for this year because I like doing just
that. Creating a new project from scratch isn't something one gets to do
often.

.formatter.exs

···
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

···
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Temporary files, for example, from tests.
+/tmp/
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+aoc2025-*.tar

README.md

···
+# Aoc2025
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `aoc2025` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:aoc2025, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at <https://hexdocs.pm/aoc2025>.

lib/aoc2025.ex

···
+defmodule Aoc2025 do
+  @moduledoc """
+  Documentation for `Aoc2025`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> Aoc2025.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

mix.exs

···
+defmodule Aoc2025.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :aoc2025,
+      version: "0.1.0",
+      elixir: "~> 1.19",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end

test/aoc2025_test.exs

···
+defmodule Aoc2025Test do
+  use ExUnit.Case
+  doctest Aoc2025
+
+  test "greets the world" do
+    assert Aoc2025.hello() == :world
+  end
+end

test/test_helper.exs

···
+ExUnit.start()