Fix handling of filenames with hash characters in tree view

Addressable::URI interprets the `#` in a URI as a URI fragment
and does not escape it, but Rails has special helpers that treats
these as bona-fide characters that need to be escaped.

Closes https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23368

app/helpers/tree_helper.rb

@@ -37,13 +37,13 @@ module TreeHelper
   # Using Rails `*_path` methods can be slow, especially when generating
   # many paths, as with a repository tree that has thousands of items.
   def fast_project_blob_path(project, blob_path)
-    Addressable::URI.escape(
+    ActionDispatch::Journey::Router::Utils.escape_path(
       File.join(relative_url_root, project.path_with_namespace, 'blob', blob_path)
     )
   end
 
   def fast_project_tree_path(project, tree_path)
-    Addressable::URI.escape(
+    ActionDispatch::Journey::Router::Utils.escape_path(
       File.join(relative_url_root, project.path_with_namespace, 'tree', tree_path)
     )
   end

changelogs/unreleased/sh-fix-hash-filename-handling.yml

+---
+title: Fix handling of filenames with hash characters in tree view
+merge_request: 23368
+author:
+type: fixed

spec/helpers/tree_helper_spec.rb

@@ -5,6 +5,16 @@ describe TreeHelper do
   let(:repository) { project.repository }
   let(:sha) { 'c1c67abbaf91f624347bb3ae96eabe3a1b742478' }
 
+  def create_file(filename)
+    project.repository.create_file(
+      project.creator,
+      filename,
+      'test this',
+      message: "Automatically created file #{filename}",
+      branch_name: 'master'
+    )
+  end
+
   describe '.render_tree' do
     before do
       @id = sha
@@ -57,6 +67,15 @@ describe TreeHelper do
 
       expect(fast_path).to start_with('/gitlab/root')
     end
+
+    it 'encodes files starting with #' do
+      filename = '#test-file'
+      create_file(filename)
+
+      fast_path = fast_project_blob_path(project, filename)
+
+      expect(fast_path).to end_with('%23test-file')
+    end
   end
 
   describe '.fast_project_tree_path' do
@@ -73,6 +92,15 @@ describe TreeHelper do
 
       expect(fast_path).to start_with('/gitlab/root')
     end
+
+    it 'encodes files starting with #' do
+      filename = '#test-file'
+      create_file(filename)
+
+      fast_path = fast_project_tree_path(project, filename)
+
+      expect(fast_path).to end_with('%23test-file')
+    end
   end
 
   describe 'flatten_tree' do