chore: still keep ctx in git.Repository struct for cat-file batch command (#38684)

Unfortunately, we can't completely remove the ctx from git.Repository,
because the CatFileBatch still heavily depends on a parent context.

If we remove the Repository ctx, the CatFileBatch will become a mess and
create a lot of unnecessary git processes.

http://localhost:3000/-/admin/monitor/perftrace

* Before: open a repo home, dozens of git processes (duplicate cat-file)
* After: only a few (no duplicate cat-file)

services/migrations/dump.go

@@ -195,7 +195,7 @@ func (g *RepositoryDumper) CreateRepo(ctx context.Context, repo *base.Repository
 		}
 	}
 
-	g.gitRepo, err = git.OpenRepositoryLocal(repoAbsPath)
+	g.gitRepo, err = git.OpenRepositoryLocal(ctx, repoAbsPath)
 	return err
 }
 

services/migrations/gitea_uploader.go

@@ -138,7 +138,7 @@ func (g *GiteaLocalUploader) CreateRepo(ctx context.Context, repo *base.Reposito
 	if err != nil {
 		return err
 	}
-	g.gitRepo, err = git.OpenRepository(g.repo)
+	g.gitRepo, err = git.OpenRepository(ctx, g.repo)
 	if err != nil {
 		return err
 	}