#171

backend/app/controllers/posts_controller.rb

@@ -177,8 +177,8 @@ class PostsController < ApplicationController
     merge = bool?(:merge)
     return head :bad_request if force && merge
 
-    base_version_no = nil
-    base_version_no = parse_base_version_no unless force
+    base_version_no = parse_base_version_no
+    return head :bad_request if !(force) && !(base_version_no)
 
     title = params[:title].presence
     tag_names = params[:tags].to_s.split
@@ -442,9 +442,11 @@ class PostsController < ApplicationController
 
   def parse_base_version_no
     version_no = Integer(params[:base_version_no], exception: false)
-    raise ArgumentError, 'base_version_no は必須です．' unless version_no&.positive?
-
-    version_no
+    if version_no&.positive?
+      version_no
+    else
+      nil
+    end
   end
 
   def post_snapshot_from_version version