git rebase exec make -C in worktree confuses repo root dir

[David Moberg <kaddkaka@gmail.com>]

Hi, I tried to minimize this but I haven't been able to come to a much
smaller example.

/David "kaddkaka" Moberg

What did you do before the bug happened? (Steps to reproduce your issue)

When doing `git rebase --exec` in a "secondary" worktree, it seems
that there is confusion about
where the repo root dir is. This sequence of commands can be run to reproduce:

  mktemp -d /tmp/git_bugreport_rebase_exec_worktree_root.XXXXXX
  cd /tmp/git_bugreport_rebase_exec_worktree_root.*
  mkdir repo
  cd repo/
  mkdir dir
  echo -e 'lint:' > dir/Makefile
  echo -e '\tgit rev-parse --show-toplevel' >> dir/Makefile
  echo -e '\tgit grep "banana" -- "$$BANANA"' >> dir/Makefile
  git init
  git add dir
  git commit -m"Intial commit"
  git worktree add ../repo2
  cd ../repo2/
  BANANA=$PWD GIT_EDITOR='sed -i "1s/noop/exec make -C dir\/ lint/"'
git rebase -i HEAD

What did you expect to happen? (Expected behavior)

1. This command should return the worktree toplevel, not a subdirectory
  $ git rev-parse --show-toplevel
  /tmp/tmp.DUUAVQCIKe/repo2

2. And the git grep command should return the match from dir/Makefile,
not Fatal Error
  $ git grep banana
  Makefile:       git grep "banana" -- "$$BANANA"

What happened instead? (Actual behavior)

1. --show-toplevel reports a subdirectory instead of toplevel:
  $ git rev-parse --show-toplevel
  /tmp/tmp.DUUAVQCIKe/repo2/dir
2. git grep complains that the pathspec is outside the repository with
fatal error:
  $ git grep "banana" -- "$BANANA"
  fatal: /tmp/tmp.DUUAVQCIKe/repo2: '/tmp/tmp.DUUAVQCIKe/repo2' is
outside repository at '/tmp/tmp.DUUAVQCIKe/repo2/dir'
  make: *** [Makefile:3: lint] Error 128
  make: Leaving directory '/tmp/tmp.DUUAVQCIKe/repo2/dir'
  warning: execution failed: make -C dir/ lint

What's different between what you expected and what actually happened?

See above.

[System Info]
git version:
git version 2.43.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Linux 6.8.0-45-generic #45-Ubuntu SMP PREEMPT_DYNAMIC Fri Aug
30 12:02:04 UTC 2024 x86_64
compiler info: gnuc: 13.2
libc info: glibc: 2.39
$SHELL (typically, interactive shell): /usr/bin/bash


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