Remove a dependency on gitlab-gollum-lib

Inlining this code allows us to remove a dependency on gitlab_grit in
gitlab-ce. We can't stop maintaining gitlab_grit yet, since gitaly-ruby
still depends on this gem, but it moves us a step closer.

lib/gitlab/git/wiki.rb

@@ -11,16 +11,11 @@ module Gitlab
           { user_id: user_id, username: username, name: name, email: email, message: message }
         end
       end
-      PageBlob = Struct.new(:name)
 
       # GollumSlug inlines just enough knowledge from Gollum::Page to generate a
       # slug, which is used when previewing pages that haven't been persisted
       class GollumSlug
         class << self
-          def format_to_ext(format)
-            format == :markdown ? 'md' : format.to_s
-          end
-
           def cname(name, char_white_sub = '-', char_other_sub = '-')
             if name.respond_to?(:gsub)
               name.gsub(/\s/, char_white_sub).gsub(/[<>+]/, char_other_sub)
@@ -29,18 +24,27 @@ module Gitlab
             end
           end
 
+          def format_to_ext(format)
+            format == :markdown ? "md" : format.to_s
+          end
+
+          def canonicalize_filename(filename)
+            ::File.basename(filename, ::File.extname(filename)).tr('-', ' ')
+          end
+
           def generate(title, format)
-            name = cname(title) + '.' + format_to_ext(format)
-            blob = PageBlob.new(name)
+            ext = format_to_ext(format.to_sym)
+            name = cname(title) + '.' + ext
+            canonical_name = canonicalize_filename(name)
 
             path =
-              if blob.name.include?('/')
-                blob.name.sub(%r{/[^/]+$}, '/')
+              if name.include?('/')
+                name.sub(%r{/[^/]+$}, '/')
               else
                 ''
               end
 
-            path + cname(name)
+            path + cname(canonical_name, '-', '-')
           end
         end
       end

spec/lib/gitlab/git/wiki_spec.rb

 require 'spec_helper'
 
 describe Gitlab::Git::Wiki do
+  using RSpec::Parameterized::TableSyntax
+
   let(:project) { create(:project) }
   let(:user) { project.owner }
   let(:project_wiki) { ProjectWiki.new(project, user) }
-  subject { project_wiki.wiki }
+
+  subject(:wiki) { project_wiki.wiki }
 
   describe '#pages' do
     before do
@@ -64,8 +67,44 @@ describe Gitlab::Git::Wiki do
     end
   end
 
-  def create_page(name, content)
-    subject.write_page(name, :markdown, content, commit_details(name))
+  describe '#preview_slug' do
+    where(:title, :format, :expected_slug) do
+      'The Best Thing'       | :markdown  | 'The-Best-Thing'
+      'The Best Thing'       | :md        | 'The-Best-Thing'
+      'The Best Thing'       | :txt       | 'The-Best-Thing'
+      'A Subject/Title Here' | :txt       | 'A-Subject/Title-Here'
+      'A subject'            | :txt       | 'A-subject'
+      'A 1/B 2/C 3'          | :txt       | 'A-1/B-2/C-3'
+      'subject/title'        | :txt       | 'subject/title'
+      'subject/title.md'     | :txt       | 'subject/title.md'
+      'foo<bar>+baz'         | :txt       | 'foo-bar--baz'
+      'foo%2Fbar'            | :txt       | 'foo%2Fbar'
+      ''                     | :markdown  | '.md'
+      ''                     | :md        | '.md'
+      ''                     | :txt       | '.txt'
+    end
+
+    with_them do
+      subject { wiki.preview_slug(title, format) }
+
+      let(:gitaly_slug) { wiki.pages.first }
+
+      it { is_expected.to eq(expected_slug) }
+
+      it 'matches the slug generated by gitaly' do
+        skip('Gitaly cannot generate a slug for an empty title') unless title.present?
+
+        create_page(title, 'content', format: format)
+
+        gitaly_slug = wiki.pages.first.url_path
+
+        is_expected.to eq(gitaly_slug)
+      end
+    end
+  end
+
+  def create_page(name, content, format: :markdown)
+    wiki.write_page(name, format, content, commit_details(name))
   end
 
   def commit_details(name)
@@ -73,7 +112,7 @@ describe Gitlab::Git::Wiki do
   end
 
   def destroy_page(title, dir = '')
-    page = subject.page(title: title, dir: dir)
+    page = wiki.page(title: title, dir: dir)
     project_wiki.delete_page(page, "test commit")
   end
 end