On Sat, 2 Jan 2021 at 02:41, Denton Liu <liu.denton@xxxxxxxxx> wrote:
>
> But then if you do
>
> $ git reflog expire --expire=now refs/heads/newbranch
> $ git commit --allow=empty -m two
> $ git show -s newbranch@{1}
>
> you'd be scolded with
>
> fatal: log for 'newbranch' only has 1 entries
>
> While it is true that it has only 1 entry, we have enough
> information in that single entry that records the transition between
> the state in which the tip of the branch was pointing at commit
> 'one' to the new commit 'two' built on it, so we should be able to
> answer "what object newbranch was pointing at?". But we refuse to
> do so.
The basic idea seems to make sense to me...
> Make @{0} the special case where we use the new side to look up that
> entry. Otherwise, look up @{n} using the old side of the (n-1)th entry
> of the reflog.
> --- a/refs.c
> +++ b/refs.c
> @@ -887,12 +887,16 @@ static int read_ref_at_ent(struct object_id *ooid, struct object_id *noid,
> const char *message, void *cb_data)
> {
> struct read_ref_at_cb *cb = cb_data;
> + int at_indexed_ent;
>
> cb->reccnt++;
> cb->tz = tz;
> cb->date = timestamp;
>
> - if (timestamp <= cb->at_time || cb->cnt == 0) {
> + if (cb->cnt > 0)
> + cb->cnt--;
> + at_indexed_ent = cb->cnt == 0 && !is_null_oid(ooid);
> + if (timestamp <= cb->at_time || at_indexed_ent) {
... but I can't really say anything about the implementation.
> +test_expect_success '@{1} works with only one reflog entry' '
> + git checkout -B newbranch &&
> + git reflog expire --expire=now refs/heads/newbranch &&
> + git commit --allow-empty -mexpired &&
Minor nit: not sure about "expired" -- maybe "first after expiration".
> + git rev-parse --verify newbranch@{1}
> +'
Should this capture the output and compare it to, e.g., `git rev-parse
newbranch^`?
> +test_expect_success '@{0} works with empty reflog' '
> + git checkout -B newbranch &&
> + git reflog expire --expire=now refs/heads/newbranch &&
> + git rev-parse --verify newbranch@{0}
> +'
Same here, but comparing to `git rev-parse newbranch`? Both of these
checks seem worthwhile to make sure that we don't just answer
*something*, but that we actually get the right answer, as per your
"redefinition".
Speaking of redefinition, does this warrant an update of the
documentation? That's a genuine question -- having browsed git-reflog(1)
and gitrevisions(7) a bit, I'm not sure.
Martin
