Merge branch 'ab/refs-various-fixes'

Code clean-up.

* ab/refs-various-fixes:
  refs debug: add a wrapper for "read_symbolic_ref"
  packed-backend: remove stub BUG(...) functions
  misc *.c: use designated initializers for struct assignments
  refs: use designated initializers for "struct ref_iterator_vtable"
  refs: use designated initializers for "struct ref_storage_be"

diff --cc attr.c
Simple merge

diff --cc object-file.c
Simple merge

diff --cc refs/files-backend.c
Simple merge

diff --cc refs/packed-backend.c
Simple merge