* extract actions on new pull request from models to pulls service
* improve code
* move code.gitea.io/gitea/modules/pull to code.gitea.io/gitea/services/pull
* fix fmt
* Rename pulls.go to pull.go
On merge we walk the merge history and ensure that all lfs objects pointed to in
the history are added to the base repository. This switches from relying on having git-lfs installed on the server, (and in fact .gitattributes being correctly installed.)