[PATCH v5 00/26] refs backend pre-vtable

This version of the series makes some minor changes from v4:

refs.c: move refname_is_safe to the common code: clarify a comment initdb: move safe_create_dir into common code: add a caveat on safe_create_dir refs.c: move update_ref to refs.c: update commit message to include write_pseudoref refs.c: move delete_pseudoref and delete_ref to the common code: remove spurious added newline refs: make files_log_ref_write functions public: reword commit message refs.c: move ref iterators to the common code: added my DCO because this patch changed a bunch since Ronnie wrote it

Thanks to Michael and Junio for the reviews.

The rest of the patches:
David Turner (9):
  refs: make is_branch public
  refs: move transaction functions into common code
  refs.c: move refname_is_safe to the common code
  refs.c: move copy_msg to the common code
  refs.c: move peel_object to the common code
  refs.c: move should_autocreate_reflog to common code
  initdb: move safe_create_dir into common code
  refs: make files_log_ref_write functions public
  refs: break out ref conflict checks

Jeff King (1):
  introduce "extensions" form of core.repositoryformatversion

Ronnie Sahlberg (16):
  refs.c: create a public version of verify_refname_available
  refs-be-files.c: rename refs to refs-be-files
  refs.c: add a new refs.c file to hold all common refs code
  refs.c: move update_ref to refs.c
  refs.c: move delete_pseudoref and delete_ref to the common code
  refs.c: move read_ref_at to the common refs file
  refs.c: move the hidden refs functions to the common code
  refs.c: move dwim and friend functions to the common refs code
  refs.c: move warn_if_dangling_symref* to the common code
  refs.c: move read_ref, read_ref_full and ref_exists to the common code
  refs.c: move resolve_refdup to common
  refs.c: move check_refname_format to the common code
  refs.c: move is_branch to the common code
  refs.c: move prettify_refname to the common code
  refs.c: move ref iterators to the common code
  refs.c: move head_ref_namespaced to the common code

 Documentation/technical/repository-version.txt |   81 +
 Makefile                                       |    1 +
 builtin/init-db.c                              |   12 -
 cache.h                                        |   11 +
 path.c                                         |   12 +
 refs-be-files.c                                | 3512 ++++++++++++++++
 refs.c                                         | 5172 ++++--------------------
 refs.h                                         |  187 +-
 setup.c                                        |   37 +-
 t/t1302-repo-version.sh                        |   38 +
 10 files changed, 4644 insertions(+), 4419 deletions(-)
 create mode 100644 Documentation/technical/repository-version.txt
 create mode 100644 refs-be-files.c