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>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"Michael McClimon" <michael@mcclimon.org>,
"John Cai" <johncai86@gmail.com>
Subject: [PATCH v5 0/2] rebase: update HEAD when is an oid
Date: Fri, 18 Mar 2022 13:54:01 +0000 [thread overview]
Message-ID: <pull.1226.v5.git.git.1647611643.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1226.v4.git.git.1647546828.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 v4:
* got rid of test assertion that shows bug behavior
* clarified commit message
changes since v3:
* fixed typos in commit message
* added a test assertion to show bug behavior
* included more replacements with test_commit
changes since v2:
* remove BUG assertion
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 | 2 ++
t/t3400-rebase.sh | 18 +++++++++++-------
2 files changed, 13 insertions(+), 7 deletions(-)
base-commit: b896f729e240d250cf56899e6a0073f6aa469f5d
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1226%2Fjohn-cai%2Fjc%2Ffix-rebase-oids-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1226/john-cai/jc/fix-rebase-oids-v5
Pull-Request: https://github.com/git/git/pull/1226
Range-diff vs v4:
1: cac51a949ee < -: ----------- rebase: test showing bug in rebase with non-branch
2: 5c40e116eba ! 1: 9dbd2ba430a rebase: use test_commit helper in setup
@@ t/t3400-rebase.sh: test_expect_success 'prepare repository with topic branches'
git checkout -f main &&
echo Third >>A &&
git update-index A &&
- git commit -m "Modify A." &&
- git checkout -b side my-topic-branch &&
-- echo Side >>C &&
-- git add C &&
-- git commit -m "Add C" &&
-+ test_commit --no-tag "Add C" C Side &&
- git checkout -f my-topic-branch &&
- git tag topic
- '
-@@ t/t3400-rebase.sh: test_expect_success 'rebase off of the previous branch using "-"' '
- test_expect_success 'rebase a single mode change' '
- git checkout main &&
- git branch -D topic &&
-- echo 1 >X &&
-- git add X &&
-- test_tick &&
-- git commit -m prepare &&
-+ test_commit prepare X 1 &&
- git checkout -b modechange HEAD^ &&
- echo 1 >X &&
- git add X &&
3: 13c5955c317 ! 2: 1dd5bb21012 rebase: set REF_HEAD_DETACH in checkout_up_to_date()
@@ Metadata
## Commit message ##
rebase: set REF_HEAD_DETACH in checkout_up_to_date()
- Fixes a bug whereby rebase updates the deferenced reference HEAD points
- to instead of HEAD directly.
-
- If HEAD is on main and if the following is a fast-forward operation,
-
- 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). See [1] for
- the original bug report.
+ "git rebase A B" where B is not a commit should behave as if the
+ HEAD got detached at B and then the detached HEAD got rebased on top
+ of A. A bug however overwrites the current branch to point at B,
+ when B is a descendant of A (i.e. the rebase ends up being a
+ fast-forward). See [1] for the original bug report.
The callstack from checkout_up_to_date() is the following:
- cmd_rebase() -> checkout_up_to_date() -> reset_head() -> update_refs()
- -> update_ref()
+ cmd_rebase()
+ -> checkout_up_to_date()
+ -> reset_head()
+ -> update_refs()
+ -> update_ref()
- When <branch> is not a valid branch but an oid, 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().
+ When B is not a valid branch but an oid, 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().
Then update_refs() checks ropts.branch to decide whether or not to switch
branches. 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 $(git
- rev-parse topic) without dereferencing it.
+ pointing to. We want the HEAD detached at B instead.
- Fix this bug by adding the RESET_HEAD_DETACH flag in checkout_up_to_date
- if <branch> is not a valid branch. so that once reset_head() calls
- update_refs(), it calls update_ref() with REF_NO_DEREF which updates
- HEAD directly intead of deferencing it and updating the branch that HEAD
- points to.
+ Fix this bug by adding the RESET_HEAD_DETACH flag in
+ checkout_up_to_date if B is not a valid branch, so that once
+ reset_head() calls update_refs(), it calls update_ref() with
+ REF_NO_DEREF which updates HEAD directly intead of deferencing it
+ and updating the branch that HEAD points to.
Also add a test to ensure the correct behavior.
- 1. https://lore.kernel.org/git/xmqqsfrpbepd.fsf@gitster.g/
+ [1] https://lore.kernel.org/git/YiokTm3GxIZQQUow@newk/
+ Reported-by: Michael McClimon <michael@mcclimon.org>
Signed-off-by: John Cai <johncai86@gmail.com>
+ Signed-off-by: Junio C Hamano <gitster@pobox.com>
## builtin/rebase.c ##
@@ builtin/rebase.c: static int checkout_up_to_date(struct rebase_options *options)
@@ t/t3400-rebase.sh: test_expect_success 'switch to branch not checked out' '
git rebase main other
'
--test_expect_success 'switch to non-branch changes branch HEAD points to' '
+test_expect_success 'switch to non-branch detaches HEAD' '
- git checkout main &&
- old_main=$(git rev-parse HEAD) &&
- git rebase First Second^0 &&
-- test_cmp_rev HEAD main &&
-- test_cmp_rev main $(git rev-parse Second) &&
-- git symbolic-ref HEAD
++ git checkout main &&
++ old_main=$(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_expect_success 'refuse to switch to branch checked out elsewhere' '
+ git checkout main &&
+ git worktree add wt &&
--
gitgitgadget
next prev parent reply other threads:[~2022-03-18 13:54 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 ` [PATCH v2 0/2] rebase: update HEAD when is an oid John Cai via GitGitGadget
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 ` John Cai via GitGitGadget [this message]
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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