Merge branch 'ds/maintenance-part-2'

"git maintenance", an extended big brother of "git gc", continues
to evolve.

* ds/maintenance-part-2:
  maintenance: add incremental-repack auto condition
  maintenance: auto-size incremental-repack batch
  maintenance: add incremental-repack task
  midx: use start_delayed_progress()
  midx: enable core.multiPackIndex by default
  maintenance: create auto condition for loose-objects
  maintenance: add loose-objects task
  maintenance: add prefetch task

diff --cc Documentation/config/core.txt
Simple merge

diff --cc midx.c
index 0de42ffdfb22c630e5b28f4997aa558c01a44d79,aa37d5da861fd15209fab7c53c43ccc1fdaf21eb..d233b54ac71a0a81fea31ab0286025802a3ed240
--- 1/midx.c
--- 2/midx.c
+++ b/midx.c
@@@ -1116,20 -1100,11 +1111,20 @@@ int verify_midx_file(struct repository 
        struct multi_pack_index *m = load_multi_pack_index(object_dir, 1);
        verify_midx_error = 0;
  
 -      if (!m)
 -              return 0;
 +      if (!m) {
 +              int result = 0;
 +              struct stat sb;
 +              char *filename = get_midx_filename(object_dir);
 +              if (!stat(filename, &sb)) {
 +                      error(_("multi-pack-index file exists, but failed to parse"));
 +                      result = 1;
 +              }
 +              free(filename);
 +              return result;
 +      }
  
        if (flags & MIDX_PROGRESS)
-               progress = start_progress(_("Looking for referenced packfiles"),
+               progress = start_delayed_progress(_("Looking for referenced packfiles"),
                                          m->num_packs);
        for (i = 0; i < m->num_packs; i++) {
                if (prepare_midx_pack(r, m, i))

diff --cc repo-settings.c
Simple merge

diff --cc repository.h
Simple merge

diff --cc t/t5319-multi-pack-index.sh
index f340b376bca55f0aa7af191f91527f8da076bf19,2f942ee1fa4ccf556ed76c1db0826e75b8917a47..ace469c95c2faaf91798639ab3d686d1637f7352
--- 1/t/t5319-multi-pack-index.sh
--- 2/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@@ -3,10 -3,9 +3,11 @@@
  test_description='multi-pack-indexes'
  . ./test-lib.sh
  
+ GIT_TEST_MULTI_PACK_INDEX=0
  objdir=.git/objects
  
 +HASH_LEN=$(test_oid rawsz)
 +
  midx_read_expect () {
        NUM_PACKS=$1
        NUM_OBJECTS=$2