more context for models (#19511)

make more usage of context, to have more db transaction in one session

(make diff of  #9307 smaller)

services/pull/patch.go

@@ -27,7 +27,7 @@ import (
 
 // DownloadDiffOrPatch will write the patch for the pr to the writer
 func DownloadDiffOrPatch(ctx context.Context, pr *models.PullRequest, w io.Writer, patch, binary bool) error {
-	if err := pr.LoadBaseRepo(); err != nil {
+	if err := pr.LoadBaseRepoCtx(ctx); err != nil {
 		log.Error("Unable to load base repository ID %d for pr #%d [%d]", pr.BaseRepoID, pr.Index, pr.ID)
 		return err
 	}