[PATCH 0/2] push: fix --force-if-includes consulting wrong ref

[Tyler Cipriani <tyler@tylercipriani.com>]

--force-if-includes has been checking the reflog of the local branch named
after the destination branch regardless of what's being pushed. This can cause
false rejections or unintended data loss.

False rejection has been reported twice that I could find:

- 2023-07-26 - Stefan Haller reported local branch with a different name
               false rejection[0]
- 2025-05-08 - D. Ben Knoble reported detached HEAD false rejection[1]

The same root cause can result in data loss: when a same-name local branch
contains the remote tip but you --force-if-includes push an unrelated branch,
clobbering the remote repo. PoCs are in t/t5533-push-cas.sh -- new test cases
fail against maint, but pass with patches applied.

Existing tests covered refspecs with different names for --force-with-lease,
but missed --force-if-includes. New patches cover:

- allow forced-update using refspec with different-named local branch
- allow same as above, but with HEAD
- reject force-update using refspec with different-named local branch lacking
  branch tip
- reject same as above using HEAD
- reject detached HEAD

Open question: the detached HEAD case. I opted to reject, since it seems like
it might be surprising to allow in the case where you were just on a branch
without the the tip of a remote ref, removed the last commit with git checkout
HEAD^ and pushed with --force-if-includes and it allowed a destructive push.
I made a separate patch showing different advice for that case (since a
git pull won't help).

Based on maint since this is a bugfix. Happy to split patches any way
that's helpful.

[0]: <https://lore.kernel.org/git/f51c73ed-eb03-83ca-fb31-d3e2645c9a63@haller-berlin.de>
[1]: <https://lore.kernel.org/git/CALnO6CCk0SgwObQRnpd5Pt_DvCKF8dBmyVHivU6Nr_O-GusGLA@mail.gmail.com>

Tyler Cipriani (2):
  push: check pushed ref for --force-if-includes
  push: fix --force-if-includes detached HEAD advice

 Documentation/config/advice.adoc |  4 ++
 advice.c                         |  1 +
 advice.h                         |  1 +
 builtin/push.c                   | 15 +++++++
 builtin/send-pack.c              |  5 +++
 remote.c                         | 27 +++++++++++-
 remote.h                         | 10 +++--
 send-pack.c                      |  1 +
 t/t5533-push-cas.sh              | 70 +++++++++++++++++++++++++++++++-
 transport-helper.c               |  5 +++
 transport.c                      |  8 ++++
 transport.h                      |  1 +
 12 files changed, 143 insertions(+), 5 deletions(-)


base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
-- 
2.47.3