refs: make errno output explicit for read_raw_ref_fn

This makes it explicit how alternative ref backends should report errors in
read_raw_ref_fn.

read_raw_ref_fn needs to supply a credible errno for a number of cases. These
are primarily:

1) The files backend calls read_raw_ref from lock_raw_ref, and uses the
resulting error codes to create/remove directories as needed.

2) ENOENT should be translated in a zero OID, optionally with REF_ISBROKEN set,
returning the last successfully resolved symref. This is necessary so
read_raw_ref("HEAD") on an empty repo returns refs/heads/main (or the default branch
du-jour), and we know on which branch to create the first commit.

Make this information flow explicit by adding a failure_errno to the signature
of read_raw_ref. All errnos from the files backend are still propagated
unchanged, even though inspection suggests only ENOTDIR, EISDIR and ENOENT are
relevant.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Han-Wen Nienhuys
2021-08-23 13:52:40 +02:00
committed by Junio C Hamano
parent 1ae6ed230a
commit 5b12e16bb1
5 changed files with 35 additions and 31 deletions

View File

@ -238,15 +238,14 @@ debug_ref_iterator_begin(struct ref_store *ref_store, const char *prefix,
static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
struct object_id *oid, struct strbuf *referent,
unsigned int *type)
unsigned int *type, int *failure_errno)
{
struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
int res = 0;
oidcpy(oid, null_oid());
errno = 0;
res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
type);
type, failure_errno);
if (res == 0) {
trace_printf_key(&trace_refs, "read_raw_ref: %s: %s (=> %s) type %x: %d\n",
@ -254,7 +253,7 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
} else {
trace_printf_key(&trace_refs,
"read_raw_ref: %s: %d (errno %d)\n", refname,
res, errno);
res, *failure_errno);
}
return res;
}