Bugfix Save wiki pages with +<> chars in title

A page's `title` will be returned from Gollum/Gitaly with any +<>
characters changed to -, whereas the `path` preserves these characters.

Previously, if a title had one of these characters in it, this method
would inaccurately return true, as we would be comparing `my+page` with
`my page` (after unhyphenization).

https://gitlab.com/gitlab-org/gitlab/-/issues/218230

app/models/wiki_page.rb

@@ -271,7 +271,10 @@ class WikiPage
 
   def title_changed?
     if persisted?
-      old_title, old_dir = wiki.page_title_and_dir(self.class.unhyphenize(page.url_path))
+      # A page's `title` will be returned from Gollum/Gitaly with any +<>
+      # characters changed to -, whereas the `path` preserves these characters.
+      path_without_extension = Pathname(page.path).sub_ext('').to_s
+      old_title, old_dir = wiki.page_title_and_dir(self.class.unhyphenize(path_without_extension))
       new_title, new_dir = wiki.page_title_and_dir(self.class.unhyphenize(title))
 
       new_title != old_title || (title.include?('/') && new_dir != old_dir)

changelogs/unreleased/218230-bugfix-save-wiki-page-modifications-with-certain-characters.yml

+---
+title: Allow wiki pages with +<> characters in their title to be saved
+merge_request: 33803
+author:
+type: fixed

spec/models/wiki_page_spec.rb

@@ -651,6 +651,7 @@ describe WikiPage do
 
     let(:untitled_page) { described_class.new(wiki) }
     let(:directory_page) { create(:wiki_page, title: 'parent directory/child page') }
+    let(:page_with_special_characters) { create(:wiki_page, title: 'test+page') }
 
     where(:page, :title, :changed) do
       :untitled_page  | nil                             | false
@@ -658,6 +659,8 @@ describe WikiPage do
 
       :new_page       | nil                             | true
       :new_page       | 'test page'                     | true
+      :new_page       | 'test-page'                     | true
+      :new_page       | 'test+page'                     | true
       :new_page       | 'new title'                     | true
 
       :existing_page  | nil                             | false
@@ -665,6 +668,7 @@ describe WikiPage do
       :existing_page  | 'test-page'                     | false
       :existing_page  | '/test page'                    | false
       :existing_page  | '/test-page'                    | false
+      :existing_page  | 'test+page'                     | true
       :existing_page  | ' test page '                   | true
       :existing_page  | 'new title'                     | true
       :existing_page  | 'new-title'                     | true
@@ -681,6 +685,11 @@ describe WikiPage do
       :directory_page | 'parent-directory / child-page' | true
       :directory_page | 'other directory/child page'    | true
       :directory_page | 'other-directory/child page'    | true
+
+      :page_with_special_characters | nil               | false
+      :page_with_special_characters | 'test+page'       | false
+      :page_with_special_characters | 'test-page'       | true
+      :page_with_special_characters | 'test page'       | true
     end
 
     with_them do