[PATCH 00/33] Various cleanups around reference packing and peeling

The highlight of this patch series are that (1) peeled references are not lost from the packed-refs file when a packed reference is deleted and (2) there is more code sharing between the code used by "git packed-refs" and the code used by repack_without_ref() for deleting a packed reference. Along the way I have added a lot of documentation and fixed several smaller bugs.

I had to add some sleeps in test t3210 but I hope that somebody can find a way to eliminate them.

The last patch implements a change that I brushed off a long time ago when Heiko suggested it. He was right (probably not for performance reasons, but because it simplifies the code).

Summary:

Patches 1-4 document existing code.

Patches 5-6 random cleanup.

Patches 7-9 change the semantics of get_packed_ref() to make it more reusable and change other locations to use this function.

Patch 10 extracts a function ref_resolves_to_object().

Patches 11-14 unify reference-peeling in two new functions, peel_object() and peel_entry() (and fix an inconsistency in peel_ref()).

Patch 15 introduces a new internal reference-iteration API and adjusts some internal code to use it. The new API gives the callback function direct access to the ref_entry. This corrects the handling of current_ref during an iteration over only packed references.

Patches 16-17 add and fix a test of a spurious error message.

Patches 18-22 change the reference-deleting code to write peeled refs to the packed-refs file. (Previously, whenever a packed reference was deleted, all of the peeled values were lost when the packed-refs file was rewritten.)

Patches 23-31 move the code from pack-refs.{c,h} into refs.{c,h}, adjust it to its new surroundings, and change it to share some code with repack_without_ref().

Patches 32-33 simplify access to the main reference cache.

Michael Haggerty (33):
  refs: document flags constants REF_*
  refs: document the fields of struct ref_value
  refs: document do_for_each_ref() and do_one_ref()
  refs: document how current_ref is used
  refs: define constant PEELED_LINE_LENGTH
  do_for_each_ref_in_dirs(): remove dead code
  get_packed_ref(): return a ref_entry
  peel_ref(): use function get_packed_ref()
  repack_without_ref(): use function get_packed_ref()
  refs: extract a function ref_resolves_to_object()
  refs: extract function peel_object()
  peel_object(): give more specific information in return value
  peel_ref(): fix return value for non-peelable, not-current reference
  refs: extract a function peel_entry()
  refs: change the internal reference-iteration API
  t3210: test for spurious error messages for dangling packed refs
  repack_without_ref(): silence errors for dangling packed refs
  search_ref_dir(): return an index rather than a pointer
  refs: change how packed refs are deleted
  t3211: demonstrate loss of peeled refs if a packed ref is deleted
  repack_without_ref(): write peeled refs in the rewritten file
  refs: extract a function write_packed_entry()
  pack-refs: rename handle_one_ref() to pack_one_ref()
  pack-refs: merge code from pack-refs.{c,h} into refs.{c,h}
  pack_one_ref(): rename "path" parameter to "refname"
  refs: use same lock_file object for both ref-packing functions
  pack_refs(): change to use do_for_each_entry()
  refs: inline function do_not_prune()
  pack_one_ref(): use function peel_entry()
  pack_one_ref(): use write_packed_entry() to do the writing
  pack_one_ref(): do some cheap tests before a more expensive one
  refs: change do_for_each_*() functions to take ref_cache arguments
  refs: handle the main ref_cache specially

 Makefile             |   2 -
 builtin/clone.c      |   1 -
 builtin/pack-refs.c  |   2 +-
 pack-refs.c          | 148 -----------
 pack-refs.h          |  18 --
 refs.c               | 699 ++++++++++++++++++++++++++++++++++++++-------------
 refs.h               |  35 +++
 t/t3210-pack-refs.sh |  36 +++
 t/t3211-peel-ref.sh  |   9 +
 9 files changed, 609 insertions(+), 341 deletions(-)
 delete mode 100644 pack-refs.c
 delete mode 100644 pack-refs.h