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

services/context/private.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"gitea.dev/modules/graceful"
+	"gitea.dev/modules/private"
 	"gitea.dev/modules/process"
 	"gitea.dev/modules/web"
 	web_types "gitea.dev/modules/web/types"
@@ -49,6 +50,14 @@ func (ctx *PrivateContext) Err() error {
 	return ctx.Base.Err()
 }
 
+func (ctx *PrivateContext) PrivateError(status int, err error, userMsg string) {
+	errMsg := ""
+	if err != nil {
+		errMsg = err.Error()
+	}
+	ctx.JSON(status, private.Response{Err: errMsg, UserMsg: userMsg})
+}
+
 type privateContextKeyType struct{}
 
 var privateContextKey privateContextKeyType