replace sync module

[6543]

replace "code.gitea.io/gitea/modules/sync" with a cluster aware one ( #13791)

ref https://github.com/go-gitea/gitea/pull/19520/files#r859289575

gitea/services/pull/pull.go

Lines 32 to 33 in 7b089c4

	// TODO: use clustered lock (unique queue? or *abuse* cache)
	var pullWorkingPool = sync.NewExclusivePool()

gitea/services/repository/transfer.go

Lines 21 to 23 in 7b089c4

	// repoWorkingPool represents a working pool to order the parallel changes to the same repository
	// TODO: use clustered lock (unique queue? or *abuse* cache)
	var repoWorkingPool = sync.NewExclusivePool()

gitea/services/wiki/wiki.go

Lines 30 to 31 in 7b089c4

	// TODO: use clustered lock (unique queue? or *abuse* cache)
	wikiWorkingPool = sync.NewExclusivePool()

[lunny]

The first one could be replaced by a unique queue at the moment to prevent there are two tasks for one pull request.

The second one could be resolved by a database transaction with optimistic lock.