Add multipart convenience argument to form_for helper.

spec/lucky/form_helpers_spec.cr

@@ -43,6 +43,18 @@ private class TestPage
       text "foo"
     end
   end
+
+  def form_with_multipart
+    form_for FormHelpers::Create, multipart: true do
+      text "foo"
+    end
+  end
+
+  def form_with_multipart_false
+    form_for FormHelpers::Create, multipart: false do
+      text "foo"
+    end
+  end
 end
 
 describe Lucky::FormHelpers do
@@ -86,6 +98,18 @@ describe Lucky::FormHelpers do
     <form action="/form_helpers" method="get"><input type="hidden" name="#{Lucky::ProtectFromForgery::PARAM_KEY}" value="my_token"></form>
     HTML
   end
+
+  it "converts the multipart argument" do
+    without_csrf_protection do
+      view(&.form_with_multipart).should contain <<-HTML
+      <form action="/form_helpers" method="post" enctype="multipart/form-data">foo</form>
+      HTML
+
+      view(&.form_with_multipart_false).should contain <<-HTML
+      <form action="/form_helpers" method="post">foo</form>
+      HTML
+    end
+  end
 end
 
 private def without_csrf_protection

src/lucky/tags/form_helpers.cr

@@ -4,8 +4,7 @@ module Lucky::FormHelpers
   end
 
   def form_for(route : Lucky::RouteHelper, **html_options) : Nil
-    form_options = {"action" => route.path, "method" => form_method(route)}
-    form merge_options(html_options, form_options) do
+    form build_form_options(route, html_options) do
       csrf_hidden_input if settings.include_csrf_tag
       method_override_input(route)
       yield
@@ -24,6 +23,16 @@ module Lucky::FormHelpers
     end
   end
 
+  private def build_form_options(route, html_options) : Hash
+    options = merge_options(html_options, {
+      "action" => route.path,
+      "method" => form_method(route),
+    })
+    options["enctype"] = "multipart/form-data" if options.delete("multipart")
+
+    options
+  end
+
   private def method_override_input(route) : Nil
     unless [:post, :get].includes? route.method
       input type: "hidden", name: "_method", value: route.method.to_s