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author | John Cai <johncai86@gmail.com> | 2022-03-18 13:54:03 +0000 |
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committer | Junio C Hamano <gitster@pobox.com> | 2022-03-18 09:48:53 -0700 |
commit | bdff97a3f6e66107abd136815c8fa1eda5c67aca (patch) | |
tree | c984c972433f4f2da9294a2b8b6de367ea55fc30 /name-hash.c | |
parent | rebase: use test_commit helper in setup (diff) | |
download | tgif-bdff97a3f6e66107abd136815c8fa1eda5c67aca.tar.xz |
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 'name-hash.c')
0 files changed, 0 insertions, 0 deletions