fix tag slug double encoding (derpibooru/philomena#203)

lib/philomena/slug.ex

@@ -47,8 +47,7 @@ defmodule Philomena.Slug do
     |> String.replace(":", "-colon-")
     |> String.replace(".", "-dot-")
     |> String.replace("+", "-plus-")
-    |> URI.encode_www_form()
-    |> String.replace("%20", "+")
+    |> String.replace(" ", "+")
   end
 
   def slug(_string), do: ""

lib/philomena_web/templates/tag/_tag.html.slime

@@ -10,7 +10,7 @@ span.tag.dropdown data-tag-category="#{@tag.category}" data-tag-id="#{@tag.id}"
     span.tag__state.hidden title="Hidden"
       | H
 
-    a.tag__name< href=Routes.tag_path(@conn, :show, @tag) title="#{@tag.short_description}" = @tag.name
+    a.tag__name< href=pretty_tag_path(@tag) title="#{@tag.short_description}" = @tag.name
 
   div.dropdown__content
     a.tag__dropdown__link.hidden data-method="delete" data-remote="true" data-tag-action="unwatch" href=Routes.tag_watch_path(@conn, :delete, @tag) Unwatch

lib/philomena_web/views/tag_view.ex

@@ -20,6 +20,10 @@ defmodule PhilomenaWeb.TagView do
     can?(conn, :alias, %Tag{})
   end
 
+  def pretty_tag_path(%{slug: slug}) do
+    "/tags/" <> URI.encode(slug, &(&1 == ?+ or URI.char_unescaped?(&1)))
+  end
+
   def tag_image(%{image: image}) do
     tag_url_root() <> "/" <> image
   end