Merge branches inside one repository using rugged instead of satellites

app/models/merge_request.rb

@@ -205,7 +205,20 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def check_if_can_be_merged
-    if Gitlab::Satellite::MergeAction.new(self.author, self).can_be_merged?
+    can_be_merged =
+      if for_fork?
+        Gitlab::Satellite::MergeAction.new(self.author, self).can_be_merged?
+      else
+        rugged = project.repository.rugged
+        our_commit = rugged.branches[target_branch].target
+        their_commit = rugged.branches[source_branch].target
+
+        if our_commit && their_commit
+          !rugged.merge_commits(our_commit, their_commit).conflicts?
+        end
+      end
+
+    if can_be_merged
       mark_as_mergeable
     else
       mark_as_unmergeable

app/models/repository.rb

@@ -414,8 +414,6 @@ class Repository
     Gitlab::Git::Blob.remove(raw_repository, options)
   end
 
-  private
-
   def user_to_comitter(user)
     {
       email: user.email,
@@ -424,6 +422,8 @@ class Repository
     }
   end
 
+  private
+
   def cache
     @cache ||= RepositoryCache.new(path_with_namespace)
   end

app/services/merge_requests/auto_merge_service.rb

@@ -5,17 +5,20 @@ module MergeRequests
   # mark merge request as merged and execute all hooks and notifications
   # Called when you do merge via GitLab UI
   class AutoMergeService < BaseMergeService
+    attr_reader :merge_request, :commit_message
+
     def execute(merge_request, commit_message)
+      @commit_message = commit_message
+      @merge_request = merge_request
+
       merge_request.lock_mr
 
-      if Gitlab::Satellite::MergeAction.new(current_user, merge_request).merge!(commit_message)
+      if merge!
         merge_request.merge
-
         create_merge_event(merge_request, current_user)
         create_note(merge_request)
         notification_service.merge_mr(merge_request, current_user)
         execute_hooks(merge_request, 'merge')
-
         true
       else
         merge_request.unlock_mr
@@ -26,5 +29,39 @@ module MergeRequests
       merge_request.mark_as_unmergeable
       false
     end
+
+    def merge!
+      if merge_request.for_fork?
+        Gitlab::Satellite::MergeAction.new(current_user, merge_request).merge!(commit_message)
+      else
+        # Merge local branches using rugged instead of satellites
+        if sha = commit
+          after_commit(sha, merge_request.target_branch)
+        end
+      end
+    end
+
+    def commit
+      committer = repository.user_to_comitter(current_user)
+
+      options = {
+        message: commit_message,
+        author: committer,
+        committer: committer
+      }
+
+      repository.merge(merge_request.source_branch, merge_request.target_branch, options)
+    end
+
+    def after_commit(sha, branch)
+      commit = repository.commit(sha)
+      full_ref = 'refs/heads/' + branch
+      old_sha = commit.parent_id || Gitlab::Git::BLANK_SHA
+      GitPushService.new.execute(project, current_user, old_sha, sha, full_ref)
+    end
+
+    def repository
+      project.repository
+    end
   end
 end