Allow browsing branches that end with '.atom'atom-routes

We need to do two things to support this:

1. Simplify the regex capture in the routing for the CommitsController
   to not exclude the '.atom' suffix. That's a perfectly valid git
   branch name, so we shouldn't blow up if we get it.
2. Because Rails now can't automatically detect the request format, add
   some code to do so in `ExtractPath` when there is no path. This means
   that, given branches 'foo' and 'foo.atom', the Atom feed for the
   former is unroutable. To fix this: don't do that! Give the branches
   different names!

5 files changed, 151 insertions, 13 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 392a356c79a..2f2396ad29f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -14,6 +14,7 @@ v 8.13.0 (unreleased)
   - Don't include archived projects when creating group milestones. !4940 (Jeroen Jacobs)
   - Add tag shortcut from the Commit page. !6543
   - Keep refs for each deployment
+  - Allow browsing branches that end with '.atom'
   - Log LDAP lookup errors and don't swallow unrelated exceptions. !6103 (Markus Koller)
   - Add more tests for calendar contribution (ClemMakesApps)
   - Cache rendered markdown in the database, rather than Redis
diff --git a/config/routes/project.rb b/config/routes/project.rb
index e8807ef06a7..4c1da5c4df5 100644
--- a/config/routes/project.rb
+++ b/config/routes/project.rb
@@ -159,7 +159,7 @@ resources :namespaces, path: '/', constraints: { id: /[a-zA-Z.0-9_\-]+/ }, only:
         get(
           '/commits/*id',
           to: 'commits#show',
-          constraints: { id: /(?:[^.]|\.(?!atom$))+/, format: /atom/ },
+          constraints: { id: /.+/, format: false },
           as: :commits
         )
       end
diff --git a/lib/extracts_path.rb b/lib/extracts_path.rb
index a4558d157c0..e4d996a3fb6 100644
--- a/lib/extracts_path.rb
+++ b/lib/extracts_path.rb
@@ -52,8 +52,7 @@ module ExtractsPath
       # Append a trailing slash if we only get a ref and no file path
       id += '/' unless id.ends_with?('/')
 
-      valid_refs = @project.repository.ref_names
-      valid_refs.select! { |v| id.start_with?("#{v}/") }
+      valid_refs = ref_names.select { |v| id.start_with?("#{v}/") }
 
       if valid_refs.length == 0
         # No exact ref match, so just try our best
@@ -74,6 +73,19 @@ module ExtractsPath
     pair
   end
 
+  # If we have an ID of 'foo.atom', and the controller provides Atom and HTML
+  # formats, then we have to check if the request was for the Atom version of
+  # the ID without the '.atom' suffix, or the HTML version of the ID including
+  # the suffix. We only check this if the version including the suffix doesn't
+  # match, so it is possible to create a branch which has an unroutable Atom
+  # feed.
+  def extract_ref_without_atom(id)
+    id_without_atom = id.sub(/\.atom$/, '')
+    valid_refs = ref_names.select { |v| "#{id_without_atom}/".start_with?("#{v}/") }
+
+    valid_refs.max_by(&:length)
+  end
+
   # Assigns common instance variables for views working with Git tree-ish objects
   #
   # Assignments are:
@@ -86,6 +98,10 @@ module ExtractsPath
   # If the :id parameter appears to be requesting a specific response format,
   # that will be handled as well.
   #
+  # If there is no path and the ref doesn't exist in the repo, try to resolve
+  # the ref without an '.atom' suffix. If _that_ ref is found, set the request's
+  # format to Atom manually.
+  #
   # Automatically renders `not_found!` if a valid tree path could not be
   # resolved (e.g., when a user inserts an invalid path or ref).
   def assign_ref_vars
@@ -103,6 +119,13 @@ module ExtractsPath
       @commit = @repo.commit(@options[:extended_sha1])
     end
 
+    if @path.empty? && !@commit
+      @id = @ref = extract_ref_without_atom(@id)
+      @commit = @repo.commit(@ref)
+
+      request.format = :atom if @commit
+    end
+
     raise InvalidPathError unless @commit
 
     @hex_path = Digest::SHA1.hexdigest(@path)
@@ -125,4 +148,10 @@ module ExtractsPath
     id += "/" + params[:path] unless params[:path].blank?
     id
   end
+
+  def ref_names
+    return [] unless @project
+
+    @ref_names ||= @project.repository.ref_names
+  end
 end
diff --git a/spec/controllers/projects/commits_controller_spec.rb b/spec/controllers/projects/commits_controller_spec.rb
index 2518a48e336..1ac7e03a2db 100644
--- a/spec/controllers/projects/commits_controller_spec.rb
+++ b/spec/controllers/projects/commits_controller_spec.rb
@@ -10,15 +10,38 @@ describe Projects::CommitsController do
   end
 
   describe "GET show" do
-    context "as atom feed" do
-      it "renders as atom" do
-        get(:show,
-            namespace_id: project.namespace.to_param,
-            project_id: project.to_param,
-            id: "master",
-            format: "atom")
-        expect(response).to be_success
-        expect(response.content_type).to eq('application/atom+xml')
+    context "when the ref name ends in .atom" do
+      render_views
+
+      context "when the ref does not exist with the suffix" do
+        it "renders as atom" do
+          get(:show,
+              namespace_id: project.namespace.to_param,
+              project_id: project.to_param,
+              id: "master.atom")
+
+          expect(response).to be_success
+          expect(response.content_type).to eq('application/atom+xml')
+        end
+      end
+
+      context "when the ref exists with the suffix" do
+        before do
+          commit = project.repository.commit('master')
+
+          allow_any_instance_of(Repository).to receive(:commit).and_call_original
+          allow_any_instance_of(Repository).to receive(:commit).with('master.atom').and_return(commit)
+
+          get(:show,
+              namespace_id: project.namespace.to_param,
+              project_id: project.to_param,
+              id: "master.atom")
+        end
+
+        it "renders as HTML" do
+          expect(response).to be_success
+          expect(response.content_type).to eq('text/html')
+        end
       end
     end
   end
diff --git a/spec/lib/extracts_path_spec.rb b/spec/lib/extracts_path_spec.rb
index e10c1f5c547..0e85e302f29 100644
--- a/spec/lib/extracts_path_spec.rb
+++ b/spec/lib/extracts_path_spec.rb
@@ -6,6 +6,7 @@ describe ExtractsPath, lib: true do
   include Gitlab::Routing.url_helpers
 
   let(:project) { double('project') }
+  let(:request) { double('request') }
 
   before do
     @project = project
@@ -15,9 +16,10 @@ describe ExtractsPath, lib: true do
     allow(project).to receive(:repository).and_return(repo)
     allow(project).to receive(:path_with_namespace).
       and_return('gitlab/gitlab-ci')
+    allow(request).to receive(:format=)
   end
 
-  describe '#assign_ref' do
+  describe '#assign_ref_vars' do
     let(:ref) { sample_commit[:id] }
     let(:params) { { path: sample_commit[:line_code_path], ref: ref } }
 
@@ -61,6 +63,75 @@ describe ExtractsPath, lib: true do
         expect(@id).to eq(get_id)
       end
     end
+
+    context 'ref only exists without .atom suffix' do
+      context 'with a path' do
+        let(:params) { { ref: 'v1.0.0.atom', path: 'README.md' } }
+
+        it 'renders a 404' do
+          expect(self).to receive(:render_404)
+
+          assign_ref_vars
+        end
+      end
+
+      context 'without a path' do
+        let(:params) { { ref: 'v1.0.0.atom' } }
+        before { assign_ref_vars }
+
+        it 'sets the un-suffixed version as @ref' do
+          expect(@ref).to eq('v1.0.0')
+        end
+
+        it 'sets the request format to Atom' do
+          expect(request).to have_received(:format=).with(:atom)
+        end
+      end
+    end
+
+    context 'ref exists with .atom suffix' do
+      context 'with a path' do
+        let(:params) { { ref: 'master.atom', path: 'README.md' } }
+
+        before do
+          repository = @project.repository
+          allow(repository).to receive(:commit).and_call_original
+          allow(repository).to receive(:commit).with('master.atom').and_return(repository.commit('master'))
+
+          assign_ref_vars
+        end
+
+        it 'sets the suffixed version as @ref' do
+          expect(@ref).to eq('master.atom')
+        end
+
+        it 'does not change the request format' do
+          expect(request).not_to have_received(:format=)
+        end
+      end
+
+      context 'without a path' do
+        let(:params) { { ref: 'master.atom' } }
+
+        before do
+          repository = @project.repository
+          allow(repository).to receive(:commit).and_call_original
+          allow(repository).to receive(:commit).with('master.atom').and_return(repository.commit('master'))
+        end
+
+        it 'sets the suffixed version as @ref' do
+          assign_ref_vars
+
+          expect(@ref).to eq('master.atom')
+        end
+
+        it 'does not change the request format' do
+          expect(request).not_to receive(:format=)
+
+          assign_ref_vars
+        end
+      end
+    end
   end
 
   describe '#extract_ref' do
@@ -115,4 +186,18 @@ describe ExtractsPath, lib: true do
       end
     end
   end
+
+  describe '#extract_ref_without_atom' do
+    it 'ignores any matching refs suffixed with atom' do
+      expect(extract_ref_without_atom('master.atom')).to eq('master')
+    end
+
+    it 'returns the longest matching ref' do
+      expect(extract_ref_without_atom('release/app/v1.0.0.atom')).to eq('release/app/v1.0.0')
+    end
+
+    it 'returns nil if there are no matching refs' do
+      expect(extract_ref_without_atom('foo.atom')).to eq(nil)
+    end
+  end
 end