Refactor modules/git global variables (#29376)

Move some global variables into a struct to improve maintainability

routers/web/repo/githttp.go

@@ -183,7 +183,7 @@ func httpBase(ctx *context.Context) *serviceHandler {
 
 		if repoExist {
 			// Because of special ref "refs/for" .. , need delay write permission check
-			if git.SupportProcReceive {
+			if git.DefaultFeatures.SupportProcReceive {
 				accessMode = perm.AccessModeRead
 			}