Merge branch 'jk/fully-peeled-packed-ref'

Merge branch 'jk/fully-peeled-packed-ref'

Not that we do not actively encourage having annotated tags outside
refs/tags/ hierarchy, but they were not advertised correctly to the
ls-remote and fetch with recent version of Git.

* jk/fully-peeled-packed-ref:
  pack-refs: add fully-peeled trait
  pack-refs: write peeled entry for non-tags
  use parse_object_or_die instead of die("bad object")
  avoid segfaults on parse_object failure