# Bug: `git switch --detach` gives inapplicable advice 4 messages from 2024-03-30 to 2024-04-05. Participants: mirth hickford, Junio C Hamano, M Hickford. Thread: https://gitlist.dev/t/61230 ## mirth hickford, 2024-03-30 07:49 Subject: Bug: `git switch --detach` gives inapplicable advice Message-ID: URL: https://gitlist.dev/e/CAKcCxfAVGr2QoaXiT81gVZ0mfq3zJs7TywRhJzevwKX7wChJ4w%40mail.gmail.com ``` Is this a bug? "Your branch can be fast-forwarded" doesn't apply to a detached HEAD. > git switch main > git reset --hard origin/main~1 > 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. ``` ## Junio C Hamano, 2024-03-30 21:37 Subject: [PATCH] checkout: do not bother "tracking" report on detached HEAD Message-ID: URL: https://gitlist.dev/e/xmqqa5mfl7ud.fsf%40gitster.g In-Reply-To: ``` 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 Signed-off-by: Junio C Hamano --- mirth hickford 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 ``` ## M Hickford, 2024-04-05 07:00 Subject: Re: [PATCH] checkout: do not bother "tracking" report on detached HEAD Message-ID: URL: https://gitlist.dev/e/CAGJzqsmE9FDEBn%3Du3ge4LA3ha4fDbm4OWiuUbMaztwjELBd7ug%40mail.gmail.com In-Reply-To: ``` On Sat, 30 Mar 2024 at 21:37, Junio C Hamano 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 > Signed-off-by: Junio C Hamano > --- > > mirth hickford 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 ``` ## Junio C Hamano, 2024-04-05 17:07 Subject: Re: [PATCH] checkout: do not bother "tracking" report on detached HEAD Message-ID: URL: https://gitlist.dev/e/xmqqzfu7viud.fsf%40gitster.g In-Reply-To: ``` M Hickford writes: > Thanks Junio for the fix. It works for me. > > Tested-by: M Hickford Thanks. It is already on 'next' and will be on 'master' sometime next week, hopefully. ```