Merge branch 'ab/die-with-bug'

Code clean-up. * ab/die-with-bug: object.c: use BUG(...) no die("BUG: ...") in lookup_object_by_type() pathspec: use BUG(...) not die("BUG:%s:%d....", <file>, <line>) strbuf.h: use BUG(...) not die("BUG: ...") pack-objects: use BUG(...) not die("BUG: ...")