From: "John Cai via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Phillip Wood <phillip.wood123@gmail.com>,
Junio C Hamano <gitster@pobox.com>,
John Cai <johncai86@gmail.com>
Subject: [PATCH v2 0/2] rebase: update HEAD when is an oid
Date: Fri, 11 Mar 2022 17:24:50 +0000 [thread overview]
Message-ID: <pull.1226.v2.git.git.1647019492.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1226.git.git.1646975144178.gitgitgadget@gmail.com>
Fixes a bug [1] reported by Michael McClimon where rebase with oids will
erroneously update the branch HEAD points to.
1. https://lore.kernel.org/git/xmqqsfrpbepd.fsf@gitster.g/
This patch has two parts:
* updates rebase setup test to add some tags we will use, while swapping
out manual commit creation with the test_commit helper
* sets RESET_HARD_DETACH flag if branch is not a valid refname
changes since v1:
* only set RESET_HEAD_DETACH if is not a valid branch
* updated tests to use existing setup
John Cai (2):
rebase: use test_commit helper in setup
rebase: set REF_HEAD_DETACH in checkout_up_to_date()
builtin/rebase.c | 5 ++++-
reset.c | 3 +++
t/t3400-rebase.sh | 18 +++++++++++-------
3 files changed, 18 insertions(+), 8 deletions(-)
base-commit: 1a4874565fa3b6668042216189551b98b4dc0b1b
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1226%2Fjohn-cai%2Fjc%2Ffix-rebase-oids-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1226/john-cai/jc/fix-rebase-oids-v2
Pull-Request: https://github.com/git/git/pull/1226
Range-diff vs v1:
-: ----------- > 1: f3f084adfa6 rebase: use test_commit helper in setup
1: 2538fd986d2 ! 2: 0e3c73375c1 rebase: set REF_HEAD_DETACH in checkout_up_to_date()
@@ Commit message
git rebase $(git rev-parse main) $(git rev-parse topic)
Instead of HEAD being set to $(git rev-parse topic), rebase erroneously
- dereferences HEAD and sets main to $(git rev-parse topic). This bug was
- reported by Michael McClimon. See [1].
+ dereferences HEAD and sets main to $(git rev-parse topic). See [1] for
+ the original bug report.
- This is happening because on a fast foward with an oid as a <branch>,
- update_refs() will only call update_ref() with REF_NO_DEREF if
- RESET_HEAD_DETACH is set. This change was made in 176f5d96 (built-in rebase
- --autostash: leave the current branch alone if possible,
- 2018-11-07). In rebase, we are not setting the RESET_HEAD_DETACH flag,
- which means that the update_ref() call ends up dereferencing
- HEAD and updating it to the oid used as <branch>.
+ The callstack from checkout_up_to_date() is the following:
+
+ cmd_rebase() -> checkout_up_to_date() -> reset_head() -> update_refs()
+ -> update_ref()
+
+ When <branch> is not a valid branch but a sha, rebase sets the head_name
+ of rebase_options to NULL. This value gets passed down this call chain
+ through the branch member of reset_head_opts also getting set to NULL
+ all the way to update_refs(). update_refs() checks ropts.branch to
+ decide whether or not to switch brancheds. If ropts.branch is NULL, it
+ calls update_ref() to update HEAD. At this point however, from rebase's
+ point of view, we want a detached HEAD. But, since checkout_up_to_date()
+ does not set the RESET_HEAD_DETACH flag, the update_ref() call will
+ deference HEAD and update the branch its pointing to, which in the above
+ example is main.
The correct behavior is that git rebase should update HEAD to $(git
rev-parse topic) without dereferencing it.
Fix this bug by adding the RESET_HEAD_DETACH flag in checkout_up_to_date
- so that once reset_head() calls update_refs(), it calls update_ref() with
- REF_NO_DEREF which updates HEAD directly intead of deferencing it and
- updating the branch that HEAD points to.
+ if <branch> is not a valid branch. so that once reset_head() calls
+ update_refs(), it calls update_ref() with REF_NO_DEREF which updates
+ HEAD directly intead of deferencing it and updating the branch that HEAD
+ points to.
Also add a test to ensure this behavior.
1. https://lore.kernel.org/git/xmqqsfrpbepd.fsf@gitster.g/
+ Reported-by: Michael McClimon <michael@mcclimon.org>
Signed-off-by: John Cai <johncai86@gmail.com>
## builtin/rebase.c ##
@@ builtin/rebase.c: static int checkout_up_to_date(struct rebase_options *options)
+ getenv(GIT_REFLOG_ACTION_ENVIRONMENT),
options->switch_to);
ropts.oid = &options->orig_head;
- ropts.branch = options->head_name;
-- ropts.flags = RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
-+ ropts.flags = RESET_HEAD_RUN_POST_CHECKOUT_HOOK | RESET_HEAD_DETACH;
+- ropts.branch = options->head_name;
+ ropts.flags = RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
++ if (options->head_name)
++ ropts.branch = options->head_name;
++ else
++ ropts.flags |= RESET_HEAD_DETACH;
ropts.head_msg = buf.buf;
if (reset_head(the_repository, &ropts) < 0)
ret = error(_("could not switch to %s"), options->switch_to);
+ ## reset.c ##
+@@ reset.c: int reset_head(struct repository *r, const struct reset_head_opts *opts)
+ if (opts->branch_msg && !opts->branch)
+ BUG("branch reflog message given without a branch");
+
++ if (switch_to_branch && opts->flags & RESET_HEAD_DETACH)
++ BUG("attempting to detach HEAD when branch is given");
++
+ if (!refs_only && repo_hold_locked_index(r, &lock, LOCK_REPORT_ON_ERROR) < 0) {
+ ret = -1;
+ goto leave_reset_head;
+
## t/t3400-rebase.sh ##
-@@ t/t3400-rebase.sh: test_expect_success 'rebase when inside worktree subdirectory' '
- )
+@@ t/t3400-rebase.sh: test_expect_success 'switch to branch not checked out' '
+ git rebase main other
'
-+test_expect_success 'rebase with oids' '
-+ git init main-wt &&
-+ (
-+ cd main-wt &&
-+ >file &&
-+ git add file &&
-+ git commit -m initial &&
-+ git checkout -b side &&
-+ echo >>file &&
-+ git commit -a -m side &&
-+ git checkout main &&
-+ git tag hold &&
-+ git checkout -B main hold &&
-+ git rev-parse main >pre &&
-+ git rebase $(git rev-parse main) $(git rev-parse side) &&
-+ git rev-parse main >post &&
-+ test "$(git rev-parse side)" = "$(cat .git/HEAD)" &&
-+ test_cmp pre post
-+ )
++test_expect_success 'switch to non-branch detaches HEAD' '
++ git checkout main &&
++ old_main=$(git rev-parse HEAD) &&
++ git rebase First Second^0 &&
++ test_cmp_rev HEAD Second &&
++ test_cmp_rev main $old_main &&
++ test_must_fail git symbolic-ref HEAD
+'
+
- test_done
+ test_expect_success 'refuse to switch to branch checked out elsewhere' '
+ git checkout main &&
+ git worktree add wt &&
--
gitgitgadget
next prev parent reply other threads:[~2022-03-11 17:24 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-11 5:05 [PATCH] rebase: set REF_HEAD_DETACH in checkout_up_to_date() John Cai via GitGitGadget
2022-03-11 5:33 ` Junio C Hamano
2022-03-11 5:55 ` Junio C Hamano
2022-03-11 14:14 ` John Cai
2022-03-11 15:05 ` Phillip Wood
2022-03-11 15:28 ` John Cai
2022-03-11 19:42 ` John Cai
2022-03-11 21:31 ` Phillip Wood
2022-03-11 17:24 ` John Cai via GitGitGadget [this message]
2022-03-11 17:24 ` [PATCH v2 1/2] rebase: use test_commit helper in setup John Cai via GitGitGadget
2022-03-13 7:50 ` Junio C Hamano
2022-03-14 10:52 ` Phillip Wood
2022-03-14 21:47 ` Junio C Hamano
2022-03-11 17:24 ` [PATCH v2 2/2] rebase: set REF_HEAD_DETACH in checkout_up_to_date() John Cai via GitGitGadget
2022-03-13 7:58 ` Junio C Hamano
2022-03-14 10:54 ` Phillip Wood
2022-03-14 14:05 ` Phillip Wood
2022-03-14 14:11 ` John Cai
2022-03-14 14:25 ` Phillip Wood
2022-03-17 3:16 ` [PATCH v3 0/2] rebase: update HEAD when is an oid John Cai via GitGitGadget
2022-03-17 3:16 ` [PATCH v3 1/2] rebase: use test_commit helper in setup John Cai via GitGitGadget
2022-03-17 13:37 ` Ævar Arnfjörð Bjarmason
2022-03-17 3:16 ` [PATCH v3 2/2] rebase: set REF_HEAD_DETACH in checkout_up_to_date() John Cai via GitGitGadget
2022-03-17 13:42 ` Ævar Arnfjörð Bjarmason
2022-03-17 15:34 ` Junio C Hamano
2022-03-17 19:53 ` [PATCH v4 0/3] rebase: update HEAD when is an oid John Cai via GitGitGadget
2022-03-17 19:53 ` [PATCH v4 1/3] rebase: test showing bug in rebase with non-branch John Cai via GitGitGadget
2022-03-17 21:10 ` Junio C Hamano
2022-03-17 21:37 ` Junio C Hamano
2022-03-17 22:44 ` John Cai
2022-03-17 19:53 ` [PATCH v4 2/3] rebase: use test_commit helper in setup John Cai via GitGitGadget
2022-03-18 11:14 ` Phillip Wood
2022-03-18 13:06 ` John Cai
2022-03-17 19:53 ` [PATCH v4 3/3] rebase: set REF_HEAD_DETACH in checkout_up_to_date() John Cai via GitGitGadget
2022-03-17 21:36 ` Junio C Hamano
2022-03-18 0:30 ` John Cai
2022-03-18 13:54 ` [PATCH v5 0/2] rebase: update HEAD when is an oid John Cai via GitGitGadget
2022-03-18 13:54 ` [PATCH v5 1/2] rebase: use test_commit helper in setup John Cai via GitGitGadget
2022-03-18 16:51 ` Junio C Hamano
2022-03-18 13:54 ` [PATCH v5 2/2] rebase: set REF_HEAD_DETACH in checkout_up_to_date() John Cai via GitGitGadget
2022-03-18 16:55 ` [PATCH v5 0/2] rebase: update HEAD when is an oid Junio C Hamano
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