Merge branch 'tb/pack-finalize-ordering' into maint

Merge branch 'tb/pack-finalize-ordering' into maint

The order in which various files that make up a single (conceptual)
packfile has been reevaluated and straightened up.  This matters in
correctness, as an incomplete set of files must not be shown to a
running Git.

* tb/pack-finalize-ordering:
  pack-objects: rename .idx files into place after .bitmap files
  pack-write: split up finish_tmp_packfile() function
  builtin/index-pack.c: move `.idx` files into place last
  index-pack: refactor renaming in final()
  builtin/repack.c: move `.idx` files into place last
  pack-write.c: rename `.idx` files after `*.rev`
  pack-write: refactor renaming in finish_tmp_packfile()
  bulk-checkin.c: store checksum directly
  pack.h: line-wrap the definition of finish_tmp_packfile()