Checking out orphan branch in new work-tree

Question

I know that a new orphan branch can be created like so:

git checkout --orphan <new_branch>

however this uses my current work tree which I want to leave completely untouched. I tried:

git --work-tree=/tmp/test checkout --orphan <new_branch>

but this also seem to use my current work tree and not the one I specified using --work-tree.

I could use a second clone, but that does not seem optimal. Any way of solving this using work-trees?

Tailing

Answer 1

Make a worktree with detached head then orphan it:

git worktree add --detach /.../dir
cd /.../dir
git checkout --orphan branch

Mandamus

d=subdir; n=some-branch; git worktree add --detach --no-checkout $d; git -C $d checkout --orphan $n; git -C $d reset; git -C $d clean -fdq; echo hello >$d/test.txt; git -C $d add test.txt; git -C $d commit -m init – Groundling

Answer 2

You can try git-worktree.

git checkout --orphan <new_branch>
git commit
git worktree add /tmp/test <new_branch>

# switch to the previous branch
git checkout -
# or
git checkout <previous_branch>

cd /tmp/test
# do something to <new_branch>

Now /tmp/test is a sub worktree. It shares the same .git with the main worktree. If you don't need the sub worktree any more, you can simply remove /tmp/test. The new commits are stored in the main repository.

If your Git does not support git-worktree yet, you need a newer version.

Arctogaea

I actually ended up with something similar here now when investigating. Just that I created the worktree first, and then did the orphan checkout there. Then I avoid switching branch in the main work tree. – Tailing

Answer 3

With Git 2.42 (Q3 2023), 'git worktree add'^(man) learned how to create a worktree based on an orphaned branch with --orphan.

So this should be supported.

See commit 926c40d, commit 128e549, commit 35f0383, commit 7ab8918, commit 9ccdace, commit ed6db0e, commit 1b28fbd, commit b71f919 (17 May 2023) by Jacob Abel (0xnu11pwn).
^{(Merged by Junio C Hamano -- gitster -- in commit 4dd0469, 22 Jun 2023)}

worktree add: introduce "try --orphan" hint

^{Signed-off-by: Jacob Abel}

Add a new advice/hint in git worktree add^(man) for when the user tries to create a new worktree from a reference that doesn't exist.

Current Behavior:

% git init foo
Initialized empty Git repository in /path/to/foo/
% touch file
% git -C foo commit -q -a -m "test commit"
% git -C foo switch --orphan norefbranch
% git -C foo worktree add newbranch/
Preparing worktree (new branch 'newbranch')
fatal: invalid reference: HEAD
%

New Behavior:

% git init --bare foo
Initialized empty Git repository in /path/to/foo/
% touch file
% git -C foo commit -q -a -m "test commit"
% git -C foo switch --orphan norefbranch
% git -C foo worktree add newbranch/
Preparing worktree (new branch 'newbranch')
hint: If you meant to create a worktree containing a new orphan branch
hint: (branch with no commits) for this repository, you can do so
hint: using the --orphan option:
hint:
hint:   git worktree add --orphan newbranch/
hint:
hint: Disable this message with "git config advice.worktreeAddOrphan false"
fatal: invalid reference: HEAD
% git -C foo worktree add -b newbranch2 new_wt/
Preparing worktree (new branch 'newbranch')
hint: If you meant to create a worktree containing a new orphan branch
hint: (branch with no commits) for this repository, you can do so
hint: using the --orphan option:
hint:
hint:   git worktree add --orphan -b newbranch2 new_wt/
hint:
hint: Disable this message with "git config advice.worktreeAddOrphan false"
fatal: invalid reference: HEAD
%

git config now includes in its man page:

worktreeAddOrphan

Advice shown when a user tries to create a worktree from an invalid reference, to instruct how to create a new orphan branch instead.

Kairouan