[v5,1/6] refs: remove EINVAL errno output from specification of read_raw_ref_fn

Commit Message

Han-Wen Nienhuys July 7, 2021, 7:07 p.m. UTC

From: Han-Wen Nienhuys <[e-mail]>

This commit does not change code; it documents the fact that an alternate ref
backend does not need to return EINVAL from read_raw_ref_fn to function
properly.

This is correct, because refs_read_raw_ref is only called from;

* resolve_ref_unsafe(), which does not care for the EINVAL errno result.

* refs_verify_refname_available(), which does not inspect errno.

* files-backend.c, where errno is overwritten on failure.

* packed-backend.c (is_packed_transaction_needed), which calls it for the
  packed ref backend, which never emits EINVAL.

A grep for EINVAL */*c reveals that no code checks errno against EINVAL after
reading references. In addition, the refs.h file does not mention errno at all.

A grep over resolve_ref_unsafe() turned up the following callers that inspect
errno:

* sequencer.c::print_commit_summary, which uses it for die_errno

* lock_ref_oid_basic(), which only treats EISDIR and ENOTDIR specially.

The files ref backend does use EINVAL. The files backend does not call into
the generic API (refs_read_raw), but into the files-specific function
(files_read_raw_ref), which we are not changing in this commit.

As the errno sideband is unintuitive and error-prone, remove EINVAL
value, as a step towards getting rid of the errno sideband altogether.

Spotted by Ævar Arnfjörð Bjarmason <[e-mail]>.

Signed-off-by: Han-Wen Nienhuys <[e-mail]>
---
 refs/refs-internal.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Patch

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 467f4b3c936..f4445e32904 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -619,9 +619,9 @@  typedef int reflog_expire_fn(struct ref_store *ref_store,
  *
  * Return 0 on success. If the ref doesn't exist, set errno to ENOENT
  * and return -1. If the ref exists but is neither a symbolic ref nor
- * an object ID, it is broken; set REF_ISBROKEN in type, set errno to
- * EINVAL, and return -1. If there is another error reading the ref,
- * set errno appropriately and return -1.
+ * an object ID, it is broken; set REF_ISBROKEN in type, and return -1
+ * (errno should not be ENOENT) If there is another error reading the
+ * ref, set errno appropriately and return -1.
  *
  * Backend-specific flags might be set in type as well, regardless of
  * outcome.