On Fri, Sep 30 2022, SZEDER Gábor wrote:
> When 'git rebase -i --update-refs' generates the todo list for the
> rebased commit range, an 'update-ref' instruction is inserted for each
> ref that points to one of those commits, except for the rebased branch
> (because at the end of the rebase it will be updated anyway) and any
> refs that are checked out in a worktree; for the latter a "Ref <ref>
> checked out at '<worktree>'" comment is added. One of these comments
> can be missing under some circumstances: if the oldest commit with a
> ref pointing to it has multiple refs pointing to it, and at least one
> of those refs is checked out in a worktree, and one of them (but not
> the first) is checked out in the worktree associated with the last
> directory entry in '.git/worktrees'.
>
> The culprit is the add_decorations_to_list() function, which calls
> resolve_ref_unsafe() to figure out the refname of the rebased branch.
> However, resolve_ref_unsafe() can (and in this case does) return a
> pointer to a static buffer. Alas, add_decorations_to_list() holds on
> that static buffer until the end of the function, using its contents
> to compare refnames with the rebased branch, while it also calls a
> function that invokes refs_resolve_ref_unsafe() internally [1], and
> which overwrites the content of that static buffer, and messes up
> subsequent refname comparisons.
>
> Use xstrdup_or_null() to keep a copy of resolve_ref_unsafe()'s return
> value for the duration of add_decorations_to_list().
>
> [1] #0 refs_resolve_ref_unsafe (refs=0x555555a23d00,
> refname=0x555555928523 "HEAD", resolve_flags=0, oid=0x555555a23c78,
> flags=0x7fffffffc0cc) at refs.c:1781
> #1 0x000055555587a1d9 in add_head_info (wt=0x555555a23c50) at worktree.c:33
> #2 0x000055555587a446 in get_linked_worktree (id=0x555555a19c43 "WorkTree")
> at worktree.c:91
> #3 0x000055555587a628 in get_worktrees () at worktree.c:135
> #4 0x00005555556a7676 in prepare_checked_out_branches () at branch.c:385
> #5 0x00005555556a7a76 in branch_checked_out (
> refname=0x555555a12e9c "refs/heads/branch2") at branch.c:446
> #6 0x0000555555824f55 in add_decorations_to_list (commit=0x5555559efd08,
> ctx=0x7fffffffc3e0) at sequencer.c:5946
>
> Signed-off-by: SZEDER Gábor <szeder.dev@xxxxxxxxx>
> ---
> sequencer.c | 5 +++--
> t/t3404-rebase-interactive.sh | 34 ++++++++++++++++++++++++++++++++++
> 2 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/sequencer.c b/sequencer.c
> index fba92c90b1..f1732f88f3 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -5917,10 +5917,10 @@ static int add_decorations_to_list(const struct commit *commit,
> struct todo_add_branch_context *ctx)
> {
> const struct name_decoration *decoration = get_name_decoration(&commit->object);
> - const char *head_ref = resolve_ref_unsafe("HEAD",
> + const char *head_ref = xstrdup_or_null(resolve_ref_unsafe("HEAD",
> RESOLVE_REF_READING,
> NULL,
> - NULL);
> + NULL));
>
> while (decoration) {
> struct todo_item *item;
> @@ -5965,6 +5965,7 @@ static int add_decorations_to_list(const struct commit *commit,
> decoration = decoration->next;
> }
>
> + free((char *)head_ref);
> return 0;
> }
>
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 7f0df58628..2e081b3914 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -2016,6 +2016,40 @@ test_expect_success REFFILES '--update-refs: check failed ref update' '
> test_cmp expect err.trimmed
> '
>
> +test_expect_success 'what should I call this?!' '
> + test_when_finished "rm -rf repo" &&
> + git init repo &&
> + (
> + cd repo &&
> + test_commit_bulk --message="%s" 4 &&
> + git branch branch1 HEAD^ &&
> + git branch branch2 HEAD^ &&
> + git branch branch3 HEAD^ &&
> +
> + git worktree add WorkTree branch2 &&
> + git worktree list --porcelain >out &&
> + wtpath=$(sed -n -e "s%^worktree \(.*/WorkTree\)%\1%p" out) &&
> +
> + cat >expect <<-EOF &&
> + pick $(git log -1 --format=%h HEAD^^) 2
> + pick $(git log -1 --format=%h HEAD^) 3
> + update-ref refs/heads/branch3
> + # Ref refs/heads/branch2 checked out at $SQ$wtpath$SQ
> + update-ref refs/heads/branch1
> + pick $(git log -1 --format=%h HEAD) 4
We can let this pass, but FWIW these are all cases where we'll lose "git
log"'s exit code. So:
first=$(git log ...) &&
[...]
cat [...]
pick $first
[...]
If we want to catch that.
