Instance/Static runtime plug

This allows to set-up an arbitrary directory which overrides most of the
static files: index.html static/ emoji/ packs/ sounds/ images/ instance/
favicon.png.

If the files are not present in the directory, the bundled ones in
priv/static will be used.

lib/pleroma/web/endpoint.ex

@@ -12,6 +12,10 @@ defmodule Pleroma.Web.Endpoint do
 
   plug(Pleroma.Plugs.UploadedMedia)
 
+  # InstanceStatic needs to be before Plug.Static to be able to override shipped-static files
+  # If you're adding new paths to `only:` you'll need to configure them in InstanceStatic as well
+  plug(Pleroma.Plugs.InstanceStatic, at: "/")
+
   plug(
     Plug.Static,
     at: "/",

lib/pleroma/web/ostatus/ostatus_controller.ex

@@ -136,7 +136,7 @@ defmodule Pleroma.Web.OStatus.OStatusController do
         "html" ->
           conn
           |> put_resp_content_type("text/html")
-          |> send_file(200, Application.app_dir(:pleroma, "priv/static/index.html"))
+          |> send_file(200, Pleroma.Plugs.InstanceStatic.file_path("index.html"))
 
         _ ->
           represent_activity(conn, format, activity, user)

lib/pleroma/web/router.ex

@@ -459,7 +459,7 @@ defmodule Fallback.RedirectController do
   def redirector(conn, _params) do
     conn
     |> put_resp_content_type("text/html")
-    |> send_file(200, Application.app_dir(:pleroma, "priv/static/index.html"))
+    |> send_file(200, Pleroma.Plugs.InstanceStatic.file_path("index.html"))
   end
 
   def registration_page(conn, params) do