Workflow for bisecting with test in a branch

I'd like to bisect using a test I've written in a different branch from the one I'm bisecting. But to do `git bisect run ./test.bash` I have to keep the new test file and an old test suite file the same during the whole `bisect` process. This turned out pretty cumbersome:

test.bash:

#!/usr/bin/env bash

set -o errexit

git show my-test-branch:test-suite-path > test-suite-path
mkdir -p test-dir
git show my-test-branch:test-dir/test-file > test-dir/test-file

run_test || exit_code=$?
git checkout .
exit "${exit_code-0}"

Console session:

git bisect start my-test-branch known-good-ancestor
git bisect run ./test.bash

Is there a more streamlined way to achieve the same thing, that is, forcing some checked-in files to not change while bisecting?

Kind regards
Victor Engmark

On Sun, Apr 27, 2025 at 10:18 AM Victor Engmark [off-list ref] wrote:

I'd like to bisect using a test I've written in a different branch from
the one I'm bisecting. But to do `git bisect run ./test.bash` I have to
keep the new test file and an old test suite file the same during the
whole `bisect` process. This turned out pretty cumbersome:

[...]

Is there a more streamlined way to achieve the same thing, that is,
forcing some checked-in files to not change while bisecting?

You could perhaps use worktrees (see
https://git-scm.com/docs/git-worktree) to have a separate worktree
with the checked-in files that shouldn't change, while performing the
bisection and building in the main worktree. If all the needed files
and directories are properly set up on the separate worktree, you
could copy them over using a single `cp -a ...` command.

Also I think that conceptually it's more the responsibility of your
build and test system, rather than the SCM, to provide you with clean,
out of source builds and tests.

Best,
Christian.