FEATURE: Multisite support for S3 image stores (#6689)

* FEATURE: Multisite support for S3 image stores

* Use File.join to concatenate all paths & fix linting on multisite/s3_store_spec.rb

lib/file_store/base_store.rb

@@ -28,6 +28,10 @@ module FileStore
       not_implemented
     end
 
+    def upload_path
+      File.join("uploads", RailsMultisite::ConnectionManagement.current_db)
+    end
+
     def has_been_uploaded?(url)
       not_implemented
     end

lib/file_store/local_store.rb

@@ -32,10 +32,6 @@ module FileStore
       "#{Discourse.asset_host}#{relative_base_url}"
     end
 
-    def upload_path
-      "/uploads/#{RailsMultisite::ConnectionManagement.current_db}"
-    end
-
     def relative_base_url
       "#{Discourse.base_uri}#{upload_path}"
     end
@@ -46,7 +42,7 @@ module FileStore
 
     def download_url(upload)
       return unless upload
-      "#{relative_base_url}/#{upload.sha1}"
+      File.join(relative_base_url, upload.sha1)
     end
 
     def cdn_url(url)
@@ -68,7 +64,7 @@ module FileStore
     end
 
     def get_path_for(type, upload_id, sha, extension)
-      "#{upload_path}/#{super(type, upload_id, sha, extension)}"
+      File.join("/", upload_path, super(type, upload_id, sha, extension))
     end
 
     def copy_file(file, path)
@@ -90,7 +86,7 @@ module FileStore
     end
 
     def public_dir
-      "#{Rails.root}/public"
+      File.join(Rails.root, "public")
     end
 
     def tombstone_dir
@@ -105,15 +101,13 @@ module FileStore
     private
 
     def list_missing(model)
-      public_directory = "#{Rails.root}/public"
-
       count = 0
       model.find_each do |upload|
 
         # could be a remote image
         next unless upload.url =~ /^\/[^\/]/
 
-        path = "#{public_directory}#{upload.url}"
+        path = "#{public_dir}#{upload.url}"
         bad = true
         begin
           bad = false if File.size(path) != 0

lib/file_store/s3_store.rb

@@ -41,9 +41,12 @@ module FileStore
       # add a "content disposition" header for "attachments"
       options[:content_disposition] = "attachment; filename=\"#{filename}\"" unless FileHelper.is_supported_image?(filename)
       # if this fails, it will throw an exception
+
+      path.prepend(File.join(upload_path, "/")) if RailsMultisite::ConnectionManagement.current_db != "default"
       path = @s3_helper.upload(file, path, options)
+
       # return the upload url
-      "#{absolute_base_url}/#{path}"
+      File.join(absolute_base_url, path)
     end
 
     def remove_file(url, path)
@@ -93,7 +96,7 @@ module FileStore
       return url if SiteSetting.Upload.s3_cdn_url.blank?
       schema = url[/^(https?:)?\/\//, 1]
       folder = @s3_helper.s3_bucket_folder_path.nil? ? "" : "#{@s3_helper.s3_bucket_folder_path}/"
-      url.sub("#{schema}#{absolute_base_url}/#{folder}", "#{SiteSetting.Upload.s3_cdn_url}/")
+      url.sub(File.join("#{schema}#{absolute_base_url}", folder), File.join(SiteSetting.Upload.s3_cdn_url, "/"))
     end
 
     def cache_avatar(avatar, user_id)