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refs: make errno output explicit for read_raw_ref_fn

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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
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20
refs/refs-internal.h
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@ -620,11 +620,15 @@ typedef int reflog_expire_fn(struct ref_store *ref_store,
* properly-formatted or even safe reference name. NEITHER INPUT NOR
* OUTPUT REFERENCE NAMES ARE VALIDATED WITHIN THIS FUNCTION.
*
* 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, and return -1
* (errno should not be ENOENT) If there is another error reading the
* ref, set errno appropriately and return -1.
* Return 0 on success, or -1 on failure. If the ref exists but is neither a
* symbolic ref nor an object ID, it is broken. In this case set REF_ISBROKEN in
* type, and return -1 (failure_errno should not be ENOENT)
*
* failure_errno provides errno codes that are interpreted beyond error
* reporting. The following error codes have special meaning:
* * ENOENT: the ref doesn't exist
* * EISDIR: ref name is a directory
* * ENOTDIR: ref prefix is not a directory
*
* Backend-specific flags might be set in type as well, regardless of
* outcome.
@ -638,9 +642,9 @@ typedef int reflog_expire_fn(struct ref_store *ref_store,
* - in all other cases, referent will be untouched, and therefore
* refname will still be valid and unchanged.
*/
typedef int read_raw_ref_fn(struct ref_store *ref_store,
const char *refname, struct object_id *oid,
struct strbuf *referent, unsigned int *type);
typedef int read_raw_ref_fn(struct ref_store *ref_store, const char *refname,
struct object_id *oid, struct strbuf *referent,
unsigned int *type, int *failure_errno);
struct ref_storage_be {
struct ref_storage_be *next;