Merge branch 'blackst0ne-squash-and-merge-in-gitlab-core-ce' into 'master'

Resolve "Squash and merge in GitLab Core (CE)"

Closes #34591

See merge request gitlab-org/gitlab-ce!18956

2 files changed, 41 insertions, 4 deletions

diff --git a/app/services/merge_requests/merge_service.rb b/app/services/merge_requests/merge_service.rb
index 2209a60a840..126da891c78 100644
--- a/app/services/merge_requests/merge_service.rb
+++ b/app/services/merge_requests/merge_service.rb
@@ -34,6 +34,19 @@ module MergeRequests
       handle_merge_error(log_message: e.message, save_message_on_model: true)
     end
 
+    def source
+      return merge_request.diff_head_sha unless merge_request.squash
+
+      squash_result = ::MergeRequests::SquashService.new(project, current_user, params).execute(merge_request)
+
+      case squash_result[:status]
+      when :success
+        squash_result[:squash_sha]
+      when :error
+        raise ::MergeRequests::MergeService::MergeError, squash_result[:message]
+      end
+    end
+
     private
 
     def error_check!
@@ -116,9 +129,5 @@ module MergeRequests
     def merge_request_info
       merge_request.to_reference(full: true)
     end
-
-    def source
-      @source ||= @merge_request.diff_head_sha
-    end
   end
 end
diff --git a/app/services/merge_requests/squash_service.rb b/app/services/merge_requests/squash_service.rb
new file mode 100644
index 00000000000..a40fb2786bd
--- /dev/null
+++ b/app/services/merge_requests/squash_service.rb
@@ -0,0 +1,28 @@
+module MergeRequests
+  class SquashService < MergeRequests::WorkingCopyBaseService
+    def execute(merge_request)
+      @merge_request = merge_request
+      @repository = target_project.repository
+
+      squash || error('Failed to squash. Should be done manually.')
+    end
+
+    def squash
+      if merge_request.commits_count < 2
+        return success(squash_sha: merge_request.diff_head_sha)
+      end
+
+      if merge_request.squash_in_progress?
+        return error('Squash task canceled: another squash is already in progress.')
+      end
+
+      squash_sha = repository.squash(current_user, merge_request)
+
+      success(squash_sha: squash_sha)
+    rescue => e
+      log_error("Failed to squash merge request #{merge_request.to_reference(full: true)}:")
+      log_error(e.message)
+      false
+    end
+  end
+end