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author | John Cai <johncai86@gmail.com> | 2022-03-18 16:54:03 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2022-03-18 19:48:53 +0300 |
commit | bdff97a3f6e66107abd136815c8fa1eda5c67aca (patch) | |
tree | c984c972433f4f2da9294a2b8b6de367ea55fc30 /t | |
parent | 77ab58c0919ea9d13251c3a1ba52b301d91e1912 (diff) |
rebase: set REF_HEAD_DETACH in checkout_up_to_date()
"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()
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. We want the HEAD detached at B instead.
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/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>
Diffstat (limited to 't')
-rwxr-xr-x | t/t3400-rebase.sh | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh index 0643d01525..d5a8ee39fc 100755 --- a/t/t3400-rebase.sh +++ b/t/t3400-rebase.sh @@ -394,6 +394,15 @@ test_expect_success 'switch to branch not checked out' ' git rebase main other ' +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_expect_success 'refuse to switch to branch checked out elsewhere' ' git checkout main && git worktree add wt && |