[PATCH v3 00/19] Improve "refs" encapsulation and speed up deletes

This is v3 of the series. I think I have addressed all of the feedback from v1 [1] and v2 [2]. Thanks to Stefan, Junio, and Peff for their feedback about v2.

There are three significant changes since v2:

* Add a patch

      delete_refs(): bail early if the packed-refs file cannot be rewritten

  that changes delete_refs() to bail early if repack_without_refs()
  fails. See the log message for the explanation.

* Add a patch

      prune_refs(): use delete_refs()

  that changes "git fetch --prune" to use delete_refs() as well. This
  is analogous to the existing patch

      prune_remote(): use delete_refs()

  (Both of these changes remove quadratic behavior that can be
  extremely expensive in repositories with many packed refs.)

* Append four more commits that change how delete_ref() interprets its
  `old_sha1` parameter, to make it consistent with
  ref_transaction_delete() and friends:

      check_branch_commit(): make first parameter const
      update_ref(): don't read old reference value before delete
      cmd_update_ref(): make logic more straightforward
      delete_ref(): use the usual convention for old_sha1

  This change was suggested by Junio [3].

The last change is good for consistency, but less important than expected in the real world. The reason is that the convention of ref_transaction_delete() is that passing NULL_SHA1 as old_sha1 is a bug (because why would somebody delete a reference that he knows not to exist?) So we don't really gain a useful third case, though we do gain a consistency check that might be useful someday. However, if you don't like this change, the last four commits can be dropped (actually, commits N-3 through N-1 are marginally useful cleanups anyway so probably only the last commit should be dropped in this case).

Other, minor changes since v2:

* Improve the commit message of "delete_refs(): make error message
  more generic".

* Better explain the change to error output caused by "prune_remote():
  use delete_refs()" in that commit's log message.

* Split the "add names for function parameters" changes into a
  separate patch.

* Fix how die() is invoked in "initial_ref_transaction_commit():
  function for initial ref creation" and remove some superfluous
  braces.

This series is also available from my GitHub account [4] as branch "init-delete-refs-api".

[1] http://thread.gmane.org/gmane.comp.version-control.git/271017 [2] http://thread.gmane.org/gmane.comp.version-control.git/271552 [3] http://article.gmane.org/gmane.comp.version-control.git/271697 [4] https://github.com/mhagger/git

Michael Haggerty (19):
  delete_ref(): move declaration to refs.h
  remove_branches(): remove temporary
  delete_ref(): handle special case more explicitly
  delete_refs(): new function for the refs API
  delete_refs(): make error message more generic
  delete_refs(): bail early if the packed-refs file cannot be rewritten
  prune_remote(): use delete_refs()
  prune_refs(): use delete_refs()
  repack_without_refs(): make function private
  initial_ref_transaction_commit(): function for initial ref creation
  refs: remove some functions from the module's public interface
  initial_ref_transaction_commit(): check for duplicate refs
  initial_ref_transaction_commit(): check for ref D/F conflicts
  refs: move the remaining ref module declarations to refs.h
  refs.h: add some parameter names to function declarations
  check_branch_commit(): make first parameter const
  update_ref(): don't read old reference value before delete
  cmd_update_ref(): make logic more straightforward
  delete_ref(): use the usual convention for old_sha1

 archive.c               |   1 +
 builtin/blame.c         |   1 +
 builtin/branch.c        |   5 +-
 builtin/clone.c         |  18 ++++-
 builtin/fast-export.c   |   1 +
 builtin/fetch.c         |  25 ++++--
 builtin/fmt-merge-msg.c |   1 +
 builtin/init-db.c       |   1 +
 builtin/log.c           |   1 +
 builtin/remote.c        |  33 +-------
 builtin/update-ref.c    |  21 ++++-
 cache.h                 |  68 ----------------
 fast-import.c           |   6 +-
 refs.c                  | 182 ++++++++++++++++++++++++++++++++++++++---
 refs.h                  | 211 +++++++++++++++++++++++++++++++-----------------
 remote-testsvn.c        |   1 +
 16 files changed, 371 insertions(+), 205 deletions(-)