Merge branch 'feature/merge-request-link-after-push' into 'master'

Merge request link after pushing

## What does this MR do?
Add API to generate new merge request urls if it is a new branch. The API will be called by gitlab-shell 

## What are the relevant issue numbers?

#18266 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5542

11 files changed, 254 insertions, 23 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 8cefaf5d70a..599ff678f82 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -104,6 +104,7 @@ v 8.11.0 (unreleased)
   - Fix importing GitLab projects with an invalid MR source project
   - Sort folders with submodules in Files view !5521
   - Each `File::exists?` replaced to `File::exist?` because of deprecate since ruby version 2.2.0
+  - Print urls to create (or view) merge requests after git push !5542 (Scott Le)
 
 v 8.10.5
   - Add a data migration to fix some missing timestamps in the members table. !5670
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index b1fb3ce5d69..f6d0d0c98f5 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -104,6 +104,7 @@ class MergeRequest < ActiveRecord::Base
   scope :from_project, ->(project) { where(source_project_id: project.id) }
   scope :merged, -> { with_state(:merged) }
   scope :closed_and_merged, -> { with_states(:closed, :merged) }
+  scope :from_source_branches, ->(branches) { where(source_branch: branches) }
 
   scope :join_project, -> { joins(:target_project) }
   scope :references_project, -> { references(:target_project) }
diff --git a/app/services/merge_requests/get_urls_service.rb b/app/services/merge_requests/get_urls_service.rb
new file mode 100644
index 00000000000..501fd135e16
--- /dev/null
+++ b/app/services/merge_requests/get_urls_service.rb
@@ -0,0 +1,52 @@
+module MergeRequests
+  class GetUrlsService < BaseService
+    attr_reader :project
+
+    def initialize(project)
+      @project = project
+    end
+
+    def execute(changes)
+      branches = get_branches(changes)
+      merge_requests_map = opened_merge_requests_from_source_branches(branches)
+      branches.map do |branch|
+        existing_merge_request = merge_requests_map[branch]
+        if existing_merge_request
+          url_for_existing_merge_request(existing_merge_request)
+        else
+          url_for_new_merge_request(branch)
+        end
+      end
+    end
+
+    private
+
+    def opened_merge_requests_from_source_branches(branches)
+      merge_requests = MergeRequest.from_project(project).opened.from_source_branches(branches)
+      merge_requests.inject({}) do |hash, mr|
+        hash[mr.source_branch] = mr
+        hash
+      end
+    end
+
+    def get_branches(changes)
+      changes_list = Gitlab::ChangesList.new(changes)
+      changes_list.map do |change|
+        next unless Gitlab::Git.branch_ref?(change[:ref])
+        Gitlab::Git.branch_name(change[:ref])
+      end.compact
+    end
+
+    def url_for_new_merge_request(branch_name)
+      merge_request_params = { source_branch: branch_name }
+      url = Gitlab::Routing.url_helpers.new_namespace_project_merge_request_url(project.namespace, project, merge_request: merge_request_params)
+      { branch_name: branch_name, url: url, new_merge_request: true }
+    end
+
+    def url_for_existing_merge_request(merge_request)
+      target_project = merge_request.target_project
+      url = Gitlab::Routing.url_helpers.namespace_project_merge_request_url(target_project.namespace, target_project, merge_request)
+      { branch_name: merge_request.source_branch, url: url, new_merge_request: false }
+    end
+  end
+end
diff --git a/lib/api/internal.rb b/lib/api/internal.rb
index 959b700de78..d8e9ac406c4 100644
--- a/lib/api/internal.rb
+++ b/lib/api/internal.rb
@@ -74,6 +74,10 @@ module API
         response
       end
 
+      get "/merge_request_urls" do
+        ::MergeRequests::GetUrlsService.new(project).execute(params[:changes])
+      end
+
       #
       # Discover user by ssh key
       #
diff --git a/lib/gitlab/changes_list.rb b/lib/gitlab/changes_list.rb
new file mode 100644
index 00000000000..95308aca95f
--- /dev/null
+++ b/lib/gitlab/changes_list.rb
@@ -0,0 +1,25 @@
+module Gitlab
+  class ChangesList
+    include Enumerable
+
+    attr_reader :raw_changes
+
+    def initialize(changes)
+      @raw_changes = changes.kind_of?(String) ? changes.lines : changes
+    end
+
+    def each(&block)
+      changes.each(&block)
+    end
+
+    def changes
+      @changes ||= begin
+        @raw_changes.map do |change|
+          next if change.blank?
+          oldrev, newrev, ref = change.strip.split(' ')
+          { oldrev: oldrev, newrev: newrev, ref: ref }
+        end.compact
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/checks/change_access.rb b/lib/gitlab/checks/change_access.rb
index 5551fac4b8b..52f117e963b 100644
--- a/lib/gitlab/checks/change_access.rb
+++ b/lib/gitlab/checks/change_access.rb
@@ -4,8 +4,8 @@ module Gitlab
       attr_reader :user_access, :project
 
       def initialize(change, user_access:, project:)
-        @oldrev, @newrev, @ref = change.split(' ')
-        @branch_name = branch_name(@ref)
+        @oldrev, @newrev, @ref = change.values_at(:oldrev, :newrev, :ref)
+        @branch_name = Gitlab::Git.branch_name(@ref)
         @user_access = user_access
         @project = project
       end
@@ -47,7 +47,7 @@ module Gitlab
       end
 
       def tag_checks
-        tag_ref = tag_name(@ref)
+        tag_ref = Gitlab::Git.tag_name(@ref)
 
         if tag_ref && protected_tag?(tag_ref) && user_access.cannot_do_action?(:admin_project)
           "You are not allowed to change existing tags on this project."
@@ -73,24 +73,6 @@ module Gitlab
       def matching_merge_request?
         Checks::MatchingMergeRequest.new(@newrev, @branch_name, @project).match?
       end
-
-      def branch_name(ref)
-        ref = @ref.to_s
-        if Gitlab::Git.branch_ref?(ref)
-          Gitlab::Git.ref_name(ref)
-        else
-          nil
-        end
-      end
-
-      def tag_name(ref)
-        ref = @ref.to_s
-        if Gitlab::Git.tag_ref?(ref)
-          Gitlab::Git.ref_name(ref)
-        else
-          nil
-        end
-      end
     end
   end
 end
diff --git a/lib/gitlab/git.rb b/lib/gitlab/git.rb
index 191bea86ac3..7584efe4fa8 100644
--- a/lib/gitlab/git.rb
+++ b/lib/gitlab/git.rb
@@ -9,6 +9,24 @@ module Gitlab
         ref.gsub(/\Arefs\/(tags|heads)\//, '')
       end
 
+      def branch_name(ref)
+        ref = ref.to_s
+        if self.branch_ref?(ref)
+          self.ref_name(ref)
+        else
+          nil
+        end
+      end
+
+      def tag_name(ref)
+        ref = ref.to_s
+        if self.tag_ref?(ref)
+          self.ref_name(ref)
+        else
+          nil
+        end
+      end
+
       def tag_ref?(ref)
         ref.start_with?(TAG_REF_PREFIX)
       end
diff --git a/lib/gitlab/git_access.rb b/lib/gitlab/git_access.rb
index 5bc70f530d2..1882eb8d050 100644
--- a/lib/gitlab/git_access.rb
+++ b/lib/gitlab/git_access.rb
@@ -76,10 +76,10 @@ module Gitlab
         return build_status_object(false, "A repository for this project does not exist yet.")
       end
 
-      changes = changes.lines if changes.kind_of?(String)
+      changes_list = Gitlab::ChangesList.new(changes)
 
       # Iterate over all changes to find if user allowed all of them to be applied
-      changes.map(&:strip).reject(&:blank?).each do |change|
+      changes_list.each do |change|
         status = change_access_check(change)
         unless status.allowed?
           # If user does not have access to make at least one change - cancel all push
diff --git a/spec/lib/gitlab/changes_list_spec.rb b/spec/lib/gitlab/changes_list_spec.rb
new file mode 100644
index 00000000000..69d86144e32
--- /dev/null
+++ b/spec/lib/gitlab/changes_list_spec.rb
@@ -0,0 +1,30 @@
+require "spec_helper"
+
+describe Gitlab::ChangesList do
+  let(:valid_changes_string) { "\n000000 570e7b2 refs/heads/my_branch\nd14d6c 6fd24d refs/heads/master" }
+  let(:invalid_changes) { 1 }
+
+  context 'when changes is a valid string' do
+    let(:changes_list) { Gitlab::ChangesList.new(valid_changes_string) }
+
+    it 'splits elements by newline character' do
+      expect(changes_list).to contain_exactly({
+        oldrev: "000000",
+        newrev: "570e7b2",
+        ref: "refs/heads/my_branch"
+      }, {
+        oldrev: "d14d6c",
+        newrev: "6fd24d",
+        ref: "refs/heads/master"
+      })
+    end
+
+    it 'behaves like a list' do
+      expect(changes_list.first).to eq({
+        oldrev: "000000",
+        newrev: "570e7b2",
+        ref: "refs/heads/my_branch"
+      })
+    end
+  end
+end
diff --git a/spec/requests/api/internal_spec.rb b/spec/requests/api/internal_spec.rb
index f6f85d6e95e..be52f88831f 100644
--- a/spec/requests/api/internal_spec.rb
+++ b/spec/requests/api/internal_spec.rb
@@ -275,6 +275,24 @@ describe API::API, api: true  do
     end
   end
 
+  describe 'GET /internal/merge_request_urls' do
+    let(:repo_name) { "#{project.namespace.name}/#{project.path}" }
+    let(:changes) { URI.escape("#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/new_branch") }
+
+    before do
+      project.team << [user, :developer]
+      get api("/internal/merge_request_urls?project=#{repo_name}&changes=#{changes}"), secret_token: secret_token
+    end
+
+    it 'returns link to create new merge request' do
+      expect(json_response).to match [{
+        "branch_name" => "new_branch",
+        "url" => "http://localhost/#{project.namespace.name}/#{project.path}/merge_requests/new?merge_request%5Bsource_branch%5D=new_branch",
+        "new_merge_request" => true
+      }]
+    end
+  end
+
   def pull(key, project, protocol = 'ssh')
     post(
       api("/internal/allowed"),
diff --git a/spec/services/merge_requests/get_urls_service_spec.rb b/spec/services/merge_requests/get_urls_service_spec.rb
new file mode 100644
index 00000000000..ec26770c3eb
--- /dev/null
+++ b/spec/services/merge_requests/get_urls_service_spec.rb
@@ -0,0 +1,100 @@
+require "spec_helper"
+
+describe MergeRequests::GetUrlsService do
+  let(:project) { create(:project, :public) }
+  let(:service) { MergeRequests::GetUrlsService.new(project) }
+  let(:source_branch) { "my_branch" }
+  let(:new_merge_request_url) { "http://localhost/#{project.namespace.name}/#{project.path}/merge_requests/new?merge_request%5Bsource_branch%5D=#{source_branch}" }
+  let(:show_merge_request_url) { "http://localhost/#{project.namespace.name}/#{project.path}/merge_requests/#{merge_request.iid}" }
+  let(:new_branch_changes) { "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+  let(:existing_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+
+  describe "#execute" do
+    shared_examples 'new_merge_request_link' do
+      it 'returns url to create new merge request' do
+        result = service.execute(changes)
+        expect(result).to match([{
+          branch_name: source_branch,
+          url: new_merge_request_url,
+          new_merge_request: true
+        }])
+      end
+    end
+
+    shared_examples 'show_merge_request_url' do
+      it 'returns url to view merge request' do
+        result = service.execute(changes)
+        expect(result).to match([{
+          branch_name: source_branch,
+          url: show_merge_request_url,
+          new_merge_request: false
+        }])
+      end
+    end
+
+    context 'pushing one completely new branch' do
+      let(:changes) { new_branch_changes }
+      it_behaves_like 'new_merge_request_link'
+    end
+
+    context 'pushing to existing branch but no merge request' do
+      let(:changes) { existing_branch_changes }
+      it_behaves_like 'new_merge_request_link'
+    end
+
+    context 'pushing to existing branch and merge request opened' do
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch) }
+      let(:changes) { existing_branch_changes }
+      it_behaves_like 'show_merge_request_url'
+    end
+
+    context 'pushing to existing branch and merge request is reopened' do
+      let!(:merge_request) { create(:merge_request, :reopened, source_project: project, source_branch: source_branch) }
+      let(:changes) { existing_branch_changes }
+      it_behaves_like 'show_merge_request_url'
+    end
+
+    context 'pushing to existing branch from forked project' do
+      let(:user) { create(:user) }
+      let!(:forked_project) { Projects::ForkService.new(project, user).execute }
+      let!(:merge_request) { create(:merge_request, source_project: forked_project, target_project: project, source_branch: source_branch) }
+      let(:changes) { existing_branch_changes }
+      # Source project is now the forked one
+      let(:service) { MergeRequests::GetUrlsService.new(forked_project) }
+      it_behaves_like 'show_merge_request_url'
+    end
+
+    context 'pushing to existing branch and merge request is closed' do
+      let!(:merge_request) { create(:merge_request, :closed, source_project: project, source_branch: source_branch) }
+      let(:changes) { existing_branch_changes }
+      it_behaves_like 'new_merge_request_link'
+    end
+
+    context 'pushing to existing branch and merge request is merged' do
+      let!(:merge_request) { create(:merge_request, :merged, source_project: project, source_branch: source_branch) }
+      let(:changes) { existing_branch_changes }
+      it_behaves_like 'new_merge_request_link'
+    end
+
+    context 'pushing new branch and existing branch (with merge request created) at once' do
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: "existing_branch") }
+      let(:new_branch_changes) { "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/new_branch" }
+      let(:existing_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/existing_branch" }
+      let(:changes) { "#{new_branch_changes}\n#{existing_branch_changes}" }
+      let(:new_merge_request_url) { "http://localhost/#{project.namespace.name}/#{project.path}/merge_requests/new?merge_request%5Bsource_branch%5D=new_branch" }
+
+      it 'returns 2 urls for both creating new and showing merge request' do
+        result = service.execute(changes)
+        expect(result).to match([{
+          branch_name: "new_branch",
+          url: new_merge_request_url,
+          new_merge_request: true
+        }, {
+          branch_name: "existing_branch",
+          url: show_merge_request_url,
+          new_merge_request: false
+        }])
+      end
+    end
+  end
+end