api for generating new merge request

DRY code + fix rubocop

Add more test cases

Append to changelog

DRY changes list

find_url service for merge_requests

use GET for getting merge request links

remove files

rename to get_url_service

reduce loop

add test case for cross project

refactor tiny thing

update changelog

5 files changed, 52 insertions, 23 deletions

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