add copy of dockerfile

tasks/docker/docker.yml

@@ -1,9 +1,15 @@
 ---
-# - name: Clone Mastodon repo
-#   git:
-#     repo: https://github.com/mastodon/mastodon.git
-#     dest: "{{ mastodon_composer_folder }}"
-#     depth: 1
+- name: Clone Mastodon repo
+  git:
+    repo: https://github.com/mastodon/mastodon.git
+    dest: /usr/src/mastodon
+    depth: 1
+
+- name: Copy Dockerfile from Mastodon repo
+  copy:
+    remote_src: true
+    src: /usr/src/mastodon/Dockerfile
+    dest: "{{ mastodon_composer_folder }}/Dockerfile"
 
 - name: Ensure mastodon folder exists
   file: