Merge branch 'kn/maintenance-is-needed' into jch

"git maintenance" command learned "is-needed" subcommand to tell if
it is necessary to perform various maintenance tasks.

* kn/maintenance-is-needed:
  maintenance: add 'is-needed' subcommand
  maintenance: add checking logic in `pack_refs_condition()`
  refs: add a `optimize_required` field to `struct ref_storage_be`
  reftable/stack: add function to check if optimization is required
  reftable/stack: return stack segments directly

diff --cc builtin/gc.c
index aad1496f07bec076326669e289a560adb2ea9964,e5ba2a2e728d8903cf87590ac2675025b7fc30cc..5fa0653ed0cf10cc110eb49839f78a56a464c9ce
--- 1/builtin/gc.c
--- 2/builtin/gc.c
+++ b/builtin/gc.c
@@@ -34,8 -34,8 +34,9 @@@
  #include "pack-objects.h"
  #include "path.h"
  #include "reflog.h"
 +#include "repack.h"
  #include "rerere.h"
+ #include "revision.h"
  #include "blob.h"
  #include "tree.h"
  #include "promisor-remote.h"

diff --cc object.h
Simple merge

diff --cc refs/debug.c
Simple merge

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

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

diff --cc t/t7900-maintenance.sh
Simple merge