[PATCH v7 0/6] refs: cleanup errno sideband ref related functions

Per the discussion & feedback on the "v6?" at [1] this is a version of Han-Wen's patches which:

 A. Goes on top of my just-submitted one-patch
    https://lore.kernel.org/git/patch-1.1-de0838fe99-20210714T111351Z-avarab@gmail.com
    being able to remove that code in lock_ref_oid_basic() makes
    things simpler, the BUG() I added to that branch in my "v6?" is
    gone.

    That change simplifies this series quite a bit, more than one
    patch in this one dealt with that now-removed codepath.

 B. Rebases this on top of that

 C. I ejected my long series of RFC-esque patches at the end.

    Per [2] it looks like Han-Wen is happy to have some version of my
    re-roll picked up, but I hardly think it's fair that I inflate
    other people's serieses with a bunch of fixes on top, I cause
    myself enough trouble with that as it is :)

    The value of those patches of mine on top is to assert that the
    changes in this series are correct.

    But I think to just get this in it's enough that that work exists
    and that we did the full errno conversion and could demonstrate
    that there weren't bugs as a result of it.

    For now in 04/06 here we leave the "For unmigrated legacy callers"
    assignment of "errno" in refs_resolve_ref_unsafe().

    I'll just submit that cleanup series on top of this once this
    lands.

1. http://lore.kernel.org/git/cover-00.17-00000000000-20210711T162803Z-avarab@gmail.com
2. http://lore.kernel.org/git/CAFQ2z_P=9Suh0kO6E44hUOyNFOAKcmcUg_x6AQFP9jhHrBA6RQ@mail.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

 refs.c                | 69 ++++++++++++++++++++----------
 refs.h                | 11 +++++
 refs/debug.c          |  4 +-
 refs/files-backend.c  | 98 +++++++++++++++++++++++--------------------
 refs/packed-backend.c | 15 +++----
 refs/refs-internal.h  | 32 ++++++++------
 6 files changed, 141 insertions(+), 88 deletions(-)

Range-diff against v6:
 1:  57517368c3 =  1:  4beba4443a refs: remove EINVAL errno output from specification of read_raw_ref_fn
 2:  61cf761147 !  2:  fd8e356185 refs/files-backend: stop setting errno from lock_ref_oid_basic
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
      	int resolve_flags = RESOLVE_REF_NO_RECURSE;
      	int resolved;
     @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
    - 		 * to remain.
    - 		 */
    - 		if (remove_empty_directories(&ref_file)) {
    --			last_errno = errno;
    - 			if (!refs_verify_refname_available(
    - 					    &refs->base,
    - 					    refname, extras, skip, err))
    -@@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
    - 						     refname, resolve_flags,
    - 						     &lock->old_oid, type);
    - 	}
    + 	resolved = !!refs_resolve_ref_unsafe(&refs->base,
    + 					     refname, resolve_flags,
    + 					     &lock->old_oid, type);
     -	if (!resolved) {
     -		last_errno = errno;
     -		if (last_errno != ENOTDIR ||
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
     -						   extras, skip, err))
     -			strbuf_addf(err, "unable to resolve reference '%s': %s",
     -				    refname, strerror(last_errno));
    --
     +	if (!resolved &&
     +	    (errno != ENOTDIR ||
     +	     /* in case of D/F conflict, try to generate a better error
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
     +					    skip, err))) {
     +		strbuf_addf(err, "unable to resolve reference '%s': %s",
     +			    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) &&
      	    refs_verify_refname_available(refs->packed_ref_store, refname,
 3:  a4e5f2d02f =  3:  913e72e9ff refs: make errno output explicit for read_raw_ref_fn
 4:  270cda29c3 =  4:  dd191768f6 refs: add failure_errno to refs_read_raw_ref() signature
 5:  f5197cdc0b =  5:  77c53dc0d9 refs: explicitly return failure_errno from parse_loose_ref_contents
 6:  96689e523f !  6:  5d4b1b4ddf 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
     -	resolved = !!refs_resolve_ref_unsafe(&refs->base,
     -					     refname, resolve_flags,
     -					     &lock->old_oid, type);
    --	if (!resolved && errno == EISDIR) {
     +	resolved = !!refs_resolve_ref_unsafe_with_errno(&refs->base, refname,
     +							resolve_flags,
     +							&lock->old_oid, type,
     +							&resolve_errno);
    -+	if (!resolved && resolve_errno == EISDIR) {
    - 		/*
    - 		 * we are trying to lock foo but we used to
    - 		 * have foo/bar which now does not exist;
    -@@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_ref_store *refs,
    - 						     &lock->old_oid, type);
    - 	}
      	if (!resolved &&
     -	    (errno != ENOTDIR ||
     +	    (resolve_errno != ENOTDIR ||
    @@ refs/files-backend.c: static struct ref_lock *lock_ref_oid_basic(struct files_re
      					    skip, err))) {
      		strbuf_addf(err, "unable to resolve reference '%s': %s",
     -			    refname, strerror(errno));
    +-
     +			    refname, strerror(resolve_errno));
      		goto error_return;
      	}
 7:  10a40c9244 <  -:  ---------- refs: make errno ignoring explicit in lock_ref_oid_basic()
 8:  ff38a3f193 <  -:  ---------- refs file-backend.c: stop setting "EBUSY" in verify_lock()
 9:  cdec272f06 <  -:  ---------- refs file-backend.c: deal with errno directly in verify_lock()
10:  bd0639945a <  -:  ---------- refs API: remove refs_read_ref_full() wrapper
11:  a359d1533b <  -:  ---------- refs API: make resolve_gitlink_ref() not set errno
12:  07d550015a <  -:  ---------- refs API: make refs_resolve_ref_unsafe() static
13:  73b7049151 <  -:  ---------- refs API: make refs_resolve_refdup() not set errno
14:  1e9de48d85 <  -:  ---------- refs API: make refs_ref_exists() not set errno
15:  446b50280b <  -:  ---------- refs API: make resolve_ref_unsafe() not set errno
16:  37c5b88d7d <  -:  ---------- refs API: make expand_ref() and repo_dwim_log() not set errno
17:  f914df0bb2 <  -:  ---------- refs API: don't leak "errno" in run_transaction_hook()