fix: git push hook post receive (#38089)

* fix incorrect delayWriter call (there is already a defer call)
* split HookPostReceive into small functions
* fix incorrect HookPostReceiveResult response for errors
* fix incorrect AddRepoToLicenseUpdaterQueue call
* make sure repo home and branches page can work without default branch
* make sure default branch is always synchronized between database and
git repo, and fix FIXME

modules/private/hook.go

@@ -48,9 +48,7 @@ type SSHLogOption struct {
 
 // HookPostReceiveResult represents an individual result from PostReceive
 type HookPostReceiveResult struct {
-	Results      []HookPostReceiveBranchResult
-	RepoWasEmpty bool
-	Err          string
+	Results []HookPostReceiveBranchResult
 }
 
 // HookPostReceiveBranchResult represents an individual branch result from PostReceive