Merge branch 'jt/fix-fattening-promisor-fetch'

Fix performance regression of a recent "fatten promisor pack with local objects" protection against an unwanted gc. * jt/fix-fattening-promisor-fetch: index-pack --promisor: also check commits' trees index-pack --promisor: don't check blobs index-pack --promisor: dedup before checking links