Sync releases table with tags on push and for mirrors (#2459)

* Sync releases table with tags on push and for mirrors

* Code style fixes

* Fix api to return only releases

* Optimize release creation and update
Minimize posibility of race conditions

* Fix release lower tag name updating

* handle tag reference update by addionally comparing commit id

models/repo.go

@@ -940,6 +940,10 @@ func MigrateRepository(doer, u *User, opts MigrateRepoOptions) (*Repository, err
 		if headBranch != nil {
 			repo.DefaultBranch = headBranch.Name
 		}
+
+		if err = SyncReleasesWithTags(repo, gitRepo); err != nil {
+			log.Error(4, "Failed to synchronize tags to releases for repository: %v", err)
+		}
 	}
 
 	if err = repo.UpdateSize(); err != nil {