[PATCH v3 0/6] update-ref: add symref support for --stdin

From: Karthik Nayak <karthik.188@gmail.com>

The 'update-ref' command is used to update refs using transactions. The command allows users to also utilize a '--stdin' mode to provide a batch of sub-commands which can be processed in a transaction.

Currently, the sub-commands involve {verify, delete, create, update} and they allow users to work with regular refs in the repository. To work with symrefs, users only have the option of using 'git-symbolic-ref', which doesn't provide transaction support to the users eventhough it uses the same behind the hood.

Recently, we modified the reference backend to add symref support, following which, 'git-symbolic-ref' also uses the transaction backend. But, it doesn't expose this to the user. To allow users to work with symrefs via transaction, this series adds support for new sub-commands {symrer-verify, symref-delete, symref-create, symref-update} to the '--stdin' mode of update-ref. These complement the existing sub-commands.

The patches 1, 5 fix small issues in the reference backends. The other patches 2, 3, 4 & 6, each add one of the new sub-commands.

The series is based off master, with 'kn/ref-transaction-symref' merged in. There seem to be no conflicts with 'next' or 'seen'.

There was some discussion [1] also about adding `old_target` support to the existing `update` command. I think its worthwhile to do this with some tests cleanup, will follow that up as a separate series.

Changes since v2:
* Based off 'ps/fixleaks' (commit: ebdbefa4fe9f618347124b37d44e517e0c6a3e4c)
which brought to light two leaks, which have been fixed.
* Adding credit where it's due.

[1]: https://lore.kernel.org/r/CAOLa=ZQW-cCV5BP_fCvuZimfkjwAzjEiqXYRPft1Wf9kAX=_bw@mail.gmail.com

I used the '--range-diff' flag for 'git-format-patch(1)' this time. Also I'm on vacation at the moment, so my responses are a bit slower than usual.

Karthik Nayak (6):
  refs: create and use `ref_update_expects_existing_old_ref()`
  update-ref: add support for 'symref-verify' command
  update-ref: add support for 'symref-delete' command
  update-ref: add support for 'symref-create' command
  reftable: pick either 'oid' or 'target' for new updates
  update-ref: add support for 'symref-update' command

 Documentation/git-update-ref.txt |  25 ++
 builtin/clone.c                  |   2 +-
 builtin/fetch.c                  |   2 +-
 builtin/receive-pack.c           |   3 +-
 builtin/update-ref.c             | 237 +++++++++++++++++-
 refs.c                           |  40 ++-
 refs.h                           |   6 +-
 refs/files-backend.c             |   3 +-
 refs/refs-internal.h             |   6 +
 refs/reftable-backend.c          |   7 +-
 t/t0600-reffiles-backend.sh      |  32 +++
 t/t1400-update-ref.sh            | 416 ++++++++++++++++++++++++++++++-
 t/t1416-ref-transaction-hooks.sh |  54 ++++
 t/t5605-clone-local.sh           |   2 +-
 14 files changed, 801 insertions(+), 34 deletions(-)

Range-diff against v2:
1:  2bbdeff798 ! 1:  cab5265c3c refs: create and use `ref_update_expects_existing_old_ref()`
    @@ Commit message
         `ref_update_expects_existing_old_ref()` and expose it internally via
         'refs-internal.h'.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## refs.c ##
2:  f509066cab ! 2:  ed54b0dfb9 update-ref: add support for 'symref-verify' command
    @@ Commit message
         divergence from behavior, but we never tested to ensure that reflog
         wasn't affected by the 'verify' command.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## Documentation/git-update-ref.txt ##
3:  a11f4c1e48 ! 3:  b82b86ff40 update-ref: add support for 'symref-delete' command
    @@ Commit message
         within a transaction, which promises atomicity of the operation and can
         be batched with other commands.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## Documentation/git-update-ref.txt ##
4:  9b71c9e07b ! 4:  ae127f7d52 update-ref: add support for 'symref-create' command
    @@ Commit message
         as a symlink. We fallback to creating a regular symref if creating the
         symlink is unsuccessful.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## Documentation/git-update-ref.txt ##
5:  a9b1a31756 ! 5:  8889dcbf40 reftable: pick either 'oid' or 'target' for new updates
    @@ Commit message
         want to introduce the 'symref-update' command in the upcoming commit,
         which would use this flow, correct it.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## refs/reftable-backend.c ##
6:  1bbbe86743 ! 6:  19d85d56c4 update-ref: add support for 'symref-update' command
    @@ Commit message
         This command supports deref mode, to ensure that we can update
         dereferenced regular refs to symrefs.
     
    +    Helped-by: Patrick Steinhardt <ps@pks.im>
    +    Helped-by: Junio C Hamano <gitster@pobox.com>
         Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
     
      ## Documentation/git-update-ref.txt ##
    @@ builtin/update-ref.c: static char *parse_next_refname(const char **next)
     +
     +	if (arg.len)
     +		return strbuf_detach(&arg, NULL);
    ++
    ++	strbuf_release(&arg);
     +	return NULL;
     +}
      
    @@ builtin/update-ref.c: static void parse_cmd_update(struct ref_transaction *trans
     +			if (repo_get_oid(the_repository, old_target, &old_oid))
     +				die("symref-update %s: invalid oid: %s", refname, old_target);
     +
    -+			old_target = NULL;
     +			have_old_oid = 1;
     +		} else if (!strcmp(old_arg, "ref")) {
     +			if (check_refname_format(old_target, REFNAME_ALLOW_ONELEVEL))
    @@ builtin/update-ref.c: static void parse_cmd_update(struct ref_transaction *trans
     +
     +	if (ref_transaction_update(transaction, refname, NULL,
     +				   have_old_oid ? &old_oid : NULL,
    -+				   new_target, old_target,
    ++				   new_target,
    ++				   have_old_oid ? NULL : old_target,
     +				   update_flags | create_reflog_flag,
     +				   msg, &err))
     +		die("%s", err.buf);