Merge branch 'jc/verify-loose-object-header' into maint

Codepaths that read from an on-disk loose object were too loose in validating what they are reading is a proper object file and sometimes read past the data they read from the disk, which has been corrected. H/t to Gustavo Grieco for reporting. * jc/verify-loose-object-header: unpack_sha1_header(): detect malformed object header streaming: make sure to notice corrupt object