threads / patch / 64407

patchrefs: don't clear oid before read_raw_ref in the debug ref backend

Subject: [PATCH] refs: don't clear oid before read_raw_ref in the debug ref backend

## tl;dr

2 messages between Oct 31, 2025 and Oct 31, 2025. Diffs are folded; open one to read it.

replies: 1people: 2as markdown or json

Xinyu Ruan via GitGitGadget· Oct 31, 2025, 03:37 UTC · lore

From: Xinyu Ruan <r200981113@gmail.com>

The debug_read_raw_ref function clears the oid to null_oid before calling read_raw_ref, which causes the oid to be lost even when read_raw_ref successfully reads the reference. This leads to failures when executing commands like "git branch new_branch <commit_id>" with GIT_TRACE_REFS=1, as the command cannot find a valid branch point because the oid is null.

Signed-off-by: Xinyu Ruan <r200981113@gmail.com>
---
    refs: don't clear oid before read_raw_ref in the debug ref backend

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2089%2FRuanXinyu%2Fref-debug-disable-clear-oid-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2089/RuanXinyu/ref-debug-disable-clear-oid-v1
Pull-Request: https://github.com/git/git/pull/2089

 refs/debug.c | 1 -
 1 file changed, 1 deletion(-)

Show changes to refs/debug.c +0 −1

diff --git a/refs/debug.c b/refs/debug.c
index 697adbd0dc..c8dde3558d 100644
--- a/refs/debug.c
+++ b/refs/debug.c
@@ -227,7 +227,6 @@ static int debug_read_raw_ref(struct ref_store *ref_store, const char *refname,
 	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
 	int res = 0;
 
-	oidcpy(oid, null_oid(ref_store->repo->hash_algo));
 	res = drefs->refs->be->read_raw_ref(drefs->refs, refname, oid, referent,
 					    type, failure_errno);
 

base-commit: a99f379adf116d53eb11957af5bab5214915f91d

-- 
gitgitgadget

Patrick Steinhardt· Oct 31, 2025, 06:48 UTC · re: Xinyu Ruan via GitGitGadget · lore

Re: [PATCH] refs: don't clear oid before read_raw_ref in the debug ref backend

On Fri, Oct 31, 2025 at 03:37:05AM +0000, Xinyu Ruan via GitGitGadget wrote:

Show 5 quoted lines

> From: Xinyu Ruan <r200981113@gmail.com>
> 
> The debug_read_raw_ref function clears the oid to null_oid before
> calling read_raw_ref, which causes the oid to be lost even when
> read_raw_ref successfully reads the reference.

This sentence doesn't quite make sense to me. If `read_raw_ref()` succeeds, wouldn't we expect that the OID was set to the target's object ID anyway? So why does it hurt to set the object ID to the null ID if it's going to get rewritten anyway?

Another question is why we were setting it to the null OID in the first place. Ideally, this should be discussed in the commit message.

> This leads to failures
> when executing commands like "git branch new_branch <commit_id>" with
> GIT_TRACE_REFS=1, as the command cannot find a valid branch point
> because the oid is null.

This smells like an issue that can be be demonstrated via a unit test. Right now though we got zero testing for `GIT_TRACE_REFS` in our test suite. Maybe this could be used as a starting point for a new test suite "t0620-ref-debug.sh" that exercises the different callbacks?

Thanks!

Patrick