From d842cd130122c6f3d3019d467040570d7d001f7a Mon Sep 17 00:00:00 2001 From: Bence Ferdinandy Date: Fri, 22 Nov 2024 13:28:45 +0100 Subject: [PATCH] refs: atomically record overwritten ref in update_symref When updating a symref with update_symref it's currently not possible to know for sure what was the previous value that was overwritten. Extend refs_update_symref under a new function name, to record the value after the ref has been locked if the caller of refs_update_symref_extended requests it via a new variable in the function call. Make the return value of the function notify the caller, if the previous value was actually not a symbolic reference. Keep the original refs_update_symref function with the same signature, but now as a wrapper around refs_update_symref_extended. Signed-off-by: Bence Ferdinandy Signed-off-by: Junio C Hamano --- refs.c | 22 ++++++++++++++++++++-- refs.h | 4 ++++ 2 files changed, 24 insertions(+), 2 deletions(-) diff --git a/refs.c b/refs.c index 5f729ed412..d80efd58f0 100644 --- a/refs.c +++ b/refs.c @@ -2115,6 +2115,13 @@ int peel_iterated_oid(struct repository *r, const struct object_id *base, struct int refs_update_symref(struct ref_store *refs, const char *ref, const char *target, const char *logmsg) +{ + return refs_update_symref_extended(refs, ref, target, logmsg, NULL); +} + +int refs_update_symref_extended(struct ref_store *refs, const char *ref, + const char *target, const char *logmsg, + struct strbuf *referent) { struct ref_transaction *transaction; struct strbuf err = STRBUF_INIT; @@ -2125,10 +2132,22 @@ int refs_update_symref(struct ref_store *refs, const char *ref, ref_transaction_update(transaction, ref, NULL, NULL, target, NULL, REF_NO_DEREF, logmsg, &err) || - ref_transaction_commit(transaction, &err)) { + ref_transaction_prepare(transaction, &err)) { ret = error("%s", err.buf); + goto cleanup; + } + if (referent && refs_read_symbolic_ref(refs, ref, referent) == NOT_A_SYMREF) { + struct object_id oid; + if (!refs_read_ref(refs, ref, &oid)) { + strbuf_addstr(referent, oid_to_hex(&oid)); + ret = NOT_A_SYMREF; + } } + if (ref_transaction_commit(transaction, &err)) + ret = error("%s", err.buf); + +cleanup: strbuf_release(&err); if (transaction) ref_transaction_free(transaction); @@ -2948,4 +2967,3 @@ int ref_update_expects_existing_old_ref(struct ref_update *update) return (update->flags & REF_HAVE_OLD) && (!is_null_oid(&update->old_oid) || update->old_target); } - diff --git a/refs.h b/refs.h index 22c2b45b8b..5c46ac9f34 100644 --- a/refs.h +++ b/refs.h @@ -584,6 +584,10 @@ int refs_copy_existing_ref(struct ref_store *refs, const char *oldref, int refs_update_symref(struct ref_store *refs, const char *refname, const char *target, const char *logmsg); +int refs_update_symref_extended(struct ref_store *refs, const char *refname, + const char *target, const char *logmsg, + struct strbuf *referent); + enum action_on_err { UPDATE_REFS_MSG_ON_ERR, UPDATE_REFS_DIE_ON_ERR,