[PATCH v9 0/7] refs: cleanup errno sideband ref related functions

A v9 re-roll of the v8, see https://lore.kernel.org/git/cover-0.7-00000000000-20210716T142032Z-avarab@gmail.com/ and more imporantly the real summary of what this is in v7 at https://lore.kernel.org/git/cover-0.6-0000000000-20210714T114301Z-avarab@gmail.com/

As noted there this topic builds on my just-re-rolled v3 removing of dead code + fixing a gc race in the refs API, at: https://lore.kernel.org/git/cover-00.12-00000000000-20210720T102051Z-avarab@gmail.com/

The changes in this v8 are merely to re-roll on top of that. There was a stray comment that didn't apply anymore with its new 12th patch. I also removed the "in case of D/F conflict..." comment the 3rd patch previously added, with the changes in the base topic I think this codepath has become easily understood enough to not need an new comment anymore (the initial version was more complex, see https://lore.kernel.org/git/95025080c16f535599826ed4f013845d712b0e8d.1625684869.git.gitgitgadget@gmail.com/).

Han-Wen Nienhuys (6):
  refs: remove EINVAL errno output from specification of read_raw_ref_fn
  refs/files-backend: stop setting errno from lock_ref_oid_basic
  refs: make errno output explicit for read_raw_ref_fn
  refs: add failure_errno to refs_read_raw_ref() signature
  refs: explicitly return failure_errno from parse_loose_ref_contents
  refs: make errno output explicit for refs_resolve_ref_unsafe

Ævar Arnfjörð Bjarmason (1):
  refs file backend: move raceproof_create_file() here

 cache.h               |  43 ----------
 object-file.c         |  68 ---------------
 refs.c                |  69 ++++++++++-----
 refs.h                |  11 +++
 refs/debug.c          |   4 +-
 refs/files-backend.c  | 195 +++++++++++++++++++++++++++++++++---------
 refs/packed-backend.c |  15 ++--
 refs/refs-internal.h  |  32 ++++---
 8 files changed, 243 insertions(+), 194 deletions(-)

Range-diff against v8:
1:  ce1ca2cf30f = 1:  b7063c5af89 refs file backend: move raceproof_create_file() here
2:  2a69bbea821 = 2:  5a63b64f53f refs: remove EINVAL errno output from specification of read_raw_ref_fn
3:  a3f80c6d2f7 ! 3:  0dd8a4c1209 refs/files-backend: stop setting errno from lock_ref_oid_basic
    @@ Commit message
         refs_reflog_exists() (which calls a function in a vtable that is not
         documented to use and/or preserve errno)
     
    -    In the case of the "errno != ENOTDIR" case that originates in 5b2d8d6f218
    -    (lock_ref_sha1_basic(): improve diagnostics for ref D/F conflicts,
    -    2015-05-11), there the "last_errno" was saved away to return it from
    -    lock_ref_oid_basic(), now that we're no longer doing that we can skip
    -    that entirely and use "errno" directly. A follow-up change will
    -    extract the specific errno we want earlier in this function.
    -
         Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
         Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
     
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
      	files_assert_main_repository(refs, "lock_ref_oid_basic");
      	assert(err);
     @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
    - 	files_ref_path(refs, &ref_file, refname);
      	if (!refs_resolve_ref_unsafe(&refs->base, refname,
      				     RESOLVE_REF_NO_RECURSE,
    --				     &lock->old_oid, type)) {
    + 				     &lock->old_oid, type)) {
     -		last_errno = errno;
    --		if (last_errno != ENOTDIR ||
    --		    !refs_verify_refname_available(&refs->base, refname,
    --						   NULL, NULL, err))
    --			strbuf_addf(err, "unable to resolve reference '%s': %s",
    + 		if (!refs_verify_refname_available(&refs->base, refname,
    + 						   NULL, NULL, err))
    + 			strbuf_addf(err, "unable to resolve reference '%s': %s",
     -				    refname, strerror(last_errno));
    --
    -+				     &lock->old_oid, type) &&
    -+	    (errno != ENOTDIR ||
    -+	     /* in case of D/F conflict, try to generate a better error
    -+	      * message. If that fails, fall back to strerror(ENOTDIR).
    -+	      */
    -+	     !refs_verify_refname_available(&refs->base, refname, NULL,
    -+					    NULL, err))) {
    -+		strbuf_addf(err, "unable to resolve reference '%s': %s",
    -+			    refname, strerror(errno));
    ++				    refname, strerror(errno));
    + 
      		goto error_return;
      	}
    - 
     @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
      	 */
      	if (is_null_oid(&lock->old_oid) &&
4:  147058c8c3d = 4:  c54fb99714a refs: make errno output explicit for read_raw_ref_fn
5:  b42a7474f18 = 5:  18825efce7d refs: add failure_errno to refs_read_raw_ref() signature
6:  93b770c8bea = 6:  57e3f246f4f refs: explicitly return failure_errno from parse_loose_ref_contents
7:  cb32b5c0526 ! 7:  4b5e168b978 refs: make errno output explicit for refs_resolve_ref_unsafe
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
      	files_ref_path(refs, &ref_file, refname);
     -	if (!refs_resolve_ref_unsafe(&refs->base, refname,
     -				     RESOLVE_REF_NO_RECURSE,
    --				     &lock->old_oid, type) &&
    --	    (errno != ENOTDIR ||
    +-				     &lock->old_oid, type)) {
     +	if (!refs_resolve_ref_unsafe_with_errno(&refs->base, refname,
     +						RESOLVE_REF_NO_RECURSE,
     +						&lock->old_oid, type,
    -+						&resolve_errno) &&
    -+	    (resolve_errno != ENOTDIR ||
    - 	     /* in case of D/F conflict, try to generate a better error
    - 	      * message. If that fails, fall back to strerror(ENOTDIR).
    - 	      */
    - 	     !refs_verify_refname_available(&refs->base, refname, NULL,
    - 					    NULL, err))) {
    - 		strbuf_addf(err, "unable to resolve reference '%s': %s",
    --			    refname, strerror(errno));
    -+			    refname, strerror(resolve_errno));
    ++						&resolve_errno)) {
    + 		if (!refs_verify_refname_available(&refs->base, refname,
    + 						   NULL, NULL, err))
    + 			strbuf_addf(err, "unable to resolve reference '%s': %s",
    +-				    refname, strerror(errno));
    ++				    refname, strerror(resolve_errno));
    + 
      		goto error_return;
      	}
    -