Add legacy routes for modified project path

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Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

config/routes/project.rb

@@ -496,4 +496,18 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
       end
     end
   end
+
+  # Legacy routes.
+  # Introduced in 12.0.
+  # Should be removed after 12.1
+  scope(path: '*namespace_id',
+        as: :namespace,
+        namespace_id: Gitlab::PathRegex.full_namespace_route_regex) do
+    scope(path: ':project_id',
+          constraints: { project_id: Gitlab::PathRegex.project_route_regex },
+          module: :projects,
+          as: :project) do
+      Gitlab::Routing.redirect_legacy_paths(self, :settings, :branches, :tags)
+    end
+  end
 end

spec/routing/project_routing_spec.rb

@@ -212,6 +212,8 @@ describe 'project routing' do
       expect(delete('/gitlab/gitlabhq/-/branches/feature%2B45/foo/bar/baz')).to route_to('projects/branches#destroy', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'feature+45/foo/bar/baz')
       expect(delete('/gitlab/gitlabhq/-/branches/feature@45/foo/bar/baz')).to route_to('projects/branches#destroy', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'feature@45/foo/bar/baz')
     end
+
+    it_behaves_like 'redirecting a legacy project path', "/gitlab/gitlabhq/branches", "/gitlab/gitlabhq/-/branches"
   end
 
   describe Projects::TagsController, 'routing' do
@@ -597,6 +599,8 @@ describe 'project routing' do
       expect(get('/gitlab/gitlabhq/-/network/ends-with.json')).to route_to('projects/network#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'ends-with.json')
       expect(get('/gitlab/gitlabhq/-/network/master?format=json')).to route_to('projects/network#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master', format: 'json')
     end
+
+    it_behaves_like 'redirecting a legacy project path', "/gitlab/gitlabhq/network/master", "/gitlab/gitlabhq/-/network/master"
   end
 
   describe Projects::GraphsController, 'routing' do
@@ -662,4 +666,12 @@ describe 'project routing' do
       end
     end
   end
+
+  describe Projects::Settings::RepositoryController, 'routing' do
+    it 'to #show' do
+      expect(get('/gitlab/gitlabhq/-/settings/repository')).to route_to('projects/settings/repository#show', namespace_id: 'gitlab', project_id: 'gitlabhq')
+    end
+
+    it_behaves_like 'redirecting a legacy project path', "/gitlab/gitlabhq/settings/repository", "/gitlab/gitlabhq/-/settings/repository"
+  end
 end

spec/support/shared_examples/legacy_path_redirect_shared_examples.rb

@@ -11,3 +11,11 @@ shared_examples 'redirecting a legacy path' do |source, target|
     expect(get(source)).not_to redirect_to(target)
   end
 end
+
+shared_examples 'redirecting a legacy project path' do |source, target|
+  include RSpec::Rails::RequestExampleGroup
+
+  it "redirects #{source} to #{target}" do
+    expect(get(source)).to redirect_to(target)
+  end
+end