Patch to add a action to resync revprop-change of subversion

update_changeset_comment.patch

diff -ur redmine_org/app/controllers/sys_controller.rb redmine/app/controllers/sys_controller.rb
--- redmine_org/app/controllers/sys_controller.rb	2014-10-22 00:42:48.000000000 +0530
+++ redmine/app/controllers/sys_controller.rb	2016-08-29 14:08:22.718880800 +0530
@@ -68,6 +68,29 @@
     render :nothing => true, :status => 404
   end
 
+  def update_changeset_comment
+    scope = Project.active.has_module(:repository)
+    project = nil
+    if params[:id].to_s =~ /^\d*$/
+      project = scope.find(params[:id])
+    else
+      project = scope.find_by_identifier(params[:id])
+    end
+    raise ActiveRecord::RecordNotFound unless project
+
+    repository = project.repository
+    rev = params[:rev]
+    revisions = repository.scm.revisions(nil, rev, rev)
+
+    changeset = repository.changesets.find_by_revision(rev)
+    changeset.update_attribute("comments", revisions.first.message)
+    changeset.scan_comment_for_issue_ids
+
+    render :nothing => true, :status => 200
+  rescue ActiveRecord::RecordNotFound
+    render :nothing => true, :status => 404
+  end
+
   protected
 
   def check_enabled
diff -ur redmine_org/config/routes.rb redmine/config/routes.rb
--- redmine_org/config/routes.rb	2014-10-22 00:42:51.000000000 +0530
+++ redmine/config/routes.rb	2016-08-29 13:45:54.388880800 +0530
@@ -337,6 +337,7 @@
   match 'sys/projects', :to => 'sys#projects', :via => :get
   match 'sys/projects/:id/repository', :to => 'sys#create_project_repository', :via => :post
   match 'sys/fetch_changesets', :to => 'sys#fetch_changesets', :via => :get
+  match 'sys/update_changeset_comment', :to => 'sys#update_changeset_comment', :via => :get
 
   match 'uploads', :to => 'attachments#upload', :via => :post
 

It's for Redmine 2.5.3. See http://d.hatena.ne.jp/miau/20110530/1306764424 for details (in Japanese).