Discard unread data of git cat-file (#29297) (#29310)

Backport #29297 by @KN4CK3R

Fixes #29101
Related #29298

Discard all read data to prevent misinterpreting existing data. Some
discard calls were missing in error cases.

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: yp05327 <576951401@qq.com>

modules/git/pipeline/lfs_nogogit.go

@@ -170,6 +170,10 @@ func FindLFSFile(repo *git.Repository, hash git.SHA1) ([]*LFSResult, error) {
 				} else {
 					break commitReadingLoop
 				}
+			default:
+				if err := git.DiscardFull(batchReader, size+1); err != nil {
+					return nil, err
+				}
 			}
 		}
 	}