Merge branch 'jk/ref-array-push'

API clean-up aournd ref-filter code.

* jk/ref-array-push:
ref-filter: factor ref_array pushing into its own function
ref-filter: make ref_array_item allocation more consistent
ref-filter: use "struct object_id" consistently

diff --cc builtin/tag.c
Simple merge

diff --cc ref-filter.c
Simple merge