On Sat, 30 Mar 2024 at 21:37, Junio C Hamano <gitster@xxxxxxxxx> wrote:
>
> By definition, a detached HEAD state is tentative and there is no
> configured "upstream" that it always wants to integrate with. But
> if you detach from a branch that is behind its upstream, e.g.,
>
> $ git checkout -t -b main origin/main
> $ git checkout main
> $ git reset --hard HEAD^
> $ git checkout --detach main
>
> you'd see "you are behind your upstream origin/main". This does not
> happen when you replace the last step in the above with any of these
>
> $ git checkout HEAD^0
> $ git checkout --detach HEAD
> $ git checkout --detach origin/main
>
> Before 32669671 (checkout: introduce --detach synonym for "git
> checkout foo^{commit}", 2011-02-08) introduced the "--detach"
> option, the rule to decide if we show the tracking information
> used to be:
>
> If --quiet is not given, and if the given branch name is a real
> local branch (i.e. the one we can compute the file path under
> .git/, like 'refs/heads/master' or "HEAD" which stand for the
> name of the current branch", then give the tracking information.
>
> to exclude things like "git checkout master^0" (which was the
> official way to detach HEAD at the commit before that commit) and
> "git checkout origin/master^0" from showing tracking information,
> but still do show the tracking information for the current branch
> for "git checkout HEAD". The introduction of an explicit option
> "--detach" broke this subtley. The new rule should have been
>
> If --quiet is given, do not bother with tracking info.
> If --detach is given, do not bother with tracking info.
>
> Otherwise, if we know that the branch name given is a real local
> branch, or if we were given "HEAD" and "HEAD" is not detached,
> then attempt to show the tracking info.
>
> but it allowed "git checkout --detach master" to also show the
> tracking info by mistake. Let's tighten the rule to fix this.
>
> Reported-by: mirth hickford <mirth.hickford@xxxxxxxxx>
> Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
> ---
>
> mirth hickford <mirth.hickford@xxxxxxxxx> writes:
>
> >> git switch --detach main
> > HEAD is now at 5a07c3bde Refactor...
> > Your branch is behind 'origin/main' by 1 commit, and can be fast-forwarded.
> > (use "git pull" to update your local branch)
> >
> >> git pull
> > You are not currently on a branch.
>
> I think the instruction meant to say "use 'git pull' with
> appropriate options to update" but had to ellide the details due
> to limited screen real estate. And it is quite expected that a
> "git pull" from a detached HEAD would not do anything.
>
> Because my local branches do not track any upstream branches, I
> have little experience with the message in question. Given
> that, I doubt that I am the best person to comment on this
> issue, but having said that, I observe that this is shared
> between "checkout" and "switch".
>
> Having said that, I think that the instruction is what is wrong.
> What is wrong is the fact that the command assumed that you want
> to keep up with the upstream of the branch you detached from.
>
> builtin/checkout.c | 3 ++-
> t/t2020-checkout-detach.sh | 5 ++++-
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index 2e8b0d18f4..26e1a64569 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -1030,7 +1030,8 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
> remove_branch_state(the_repository, !opts->quiet);
> strbuf_release(&msg);
> if (!opts->quiet &&
> - (new_branch_info->path || (!opts->force_detach && !strcmp(new_branch_info->name, "HEAD"))))
> + !opts->force_detach &&
> + (new_branch_info->path || !strcmp(new_branch_info->name, "HEAD")))
> report_tracking(new_branch_info);
> }
>
> diff --git a/t/t2020-checkout-detach.sh b/t/t2020-checkout-detach.sh
> index bce284c297..8d90d02850 100755
> --- a/t/t2020-checkout-detach.sh
> +++ b/t/t2020-checkout-detach.sh
> @@ -176,7 +176,10 @@ test_expect_success 'tracking count is accurate after orphan check' '
> git config branch.child.merge refs/heads/main &&
> git checkout child^ &&
> git checkout child >stdout &&
> - test_cmp expect stdout
> + test_cmp expect stdout &&
> +
> + git checkout --detach child >stdout &&
> + test_grep ! "can be fast-forwarded\." stdout
> '
>
> test_expect_success 'no advice given for explicit detached head state' '
> --
> 2.44.0-413-gd6fd04375f
>
>
>
Thanks Junio for the fix. It works for me.
Tested-by: M Hickford <mirth.hickford@xxxxxxxxx>
