# bugreport: "git checkout -B" allows checking out one branch across multiple worktrees 4 messages from 2023-01-14 to 2023-01-16. Participants: Jinwook Jeong, Carlo Marcelo Arenas Belón, Eric Sunshine. Thread: https://gitlist.dev/t/59089 ## Jinwook Jeong, 2023-01-14 09:45 Subject: bugreport: "git checkout -B" allows checking out one branch across multiple worktrees Message-ID: URL: https://gitlist.dev/e/CAA3Q-aaO%3DvcZd9VLFr8UP-g06be80eUWN_GjygfyGkYmrLx9yQ%40mail.gmail.com ``` What did you do before the bug happened? (Steps to reproduce your issue) 1. `cd` into any git repo that has at least one commit. 2. Identify the current branch, say main 3. $ git branch foo # a new branch 4. $ git worktree add ../new_worktree foo 5. $ cd ../new_worktree 6. $ git checkout -B master HEAD What did you expect to happen? (Expected behavior) git prints out "Fatal: 'main' is already checked out at ..." (or similar message that informs me that I'm not allowed to doubly checkout one branch) What happened instead? (Actual behavior) The new_worktree successfully changes its current branch to master, which is already held by another worktree. Anything else you want to add: https://www.git-scm.com/docs/git-checkout#Documentation/git-checkout.txt-emgitcheckoutem-b-Bltnew-branchgtltstart-pointgt According to the documentation, "git checkout -B BRANCH START" is the transactionally equivalent of: git branch -f BRANCH START git checkout BRANCH When I ran the first command in place of the step 6 of the above reproducing procedure, git refused to carry on; I suppose that this is the intended behavior for "git checkout -B". [System Info] git version: git version 2.39.0 cpu: arm64 no commit associated with this build sizeof-long: 8 sizeof-size_t: 8 shell-path: /bin/sh feature: fsmonitor--daemon uname: Darwin 21.6.0 Darwin Kernel Version 21.6.0: Sun Nov 6 23:31:13 PST 2022; root:xnu-8020.240.14~1/RELEASE_ARM64_T6000 arm64 compiler info: clang: 14.0.0 (clang-1400.0.29.202) libc info: no libc information available $SHELL (typically, interactive shell): /opt/homebrew/bin/bash [Enabled Hooks] not run from a git repository - no hooks to show ``` ## Carlo Marcelo Arenas Belón, 2023-01-16 00:11 Subject: Re: bugreport: "git checkout -B" allows checking out one branch across multiple worktrees Message-ID: <20230116001144.dt76xk6hkwn45klz@Carlos-MacBook-Pro-2.local> URL: https://gitlist.dev/e/20230116001144.dt76xk6hkwn45klz%40Carlos-MacBook-Pro-2.local In-Reply-To: ``` On Sat, Jan 14, 2023 at 06:45:34PM +0900, Jinwook Jeong wrote: > What did you do before the bug happened? (Steps to reproduce your issue) > > 1. `cd` into any git repo that has at least one commit. > 2. Identify the current branch, say main > 3. $ git branch foo # a new branch > 4. $ git worktree add ../new_worktree foo > 5. $ cd ../new_worktree > 6. $ git checkout -B master HEAD Was your intention to get this worktree's content back to what is in master's HEAD?, then the command should had been $ git reset --hard master The documentation might be confusing, but you most likely do NOT want to use -B unless you want to force things, but the lowercase version `-b` > Anything else you want to add: > > https://www.git-scm.com/docs/git-checkout#Documentation/git-checkout.txt-emgitcheckoutem-b-Bltnew-branchgtltstart-pointgt > > According to the documentation, "git checkout -B BRANCH START" is the > transactionally equivalent of: > > git branch -f BRANCH START > git checkout BRANCH > > When I ran the first command in place of the step 6 of the above > reproducing procedure, git refused to carry on; > I suppose that this is the intended behavior for "git checkout -B". I think you are correct, and this is therefore a bug, but there is also a reason why `--force` allows doing dangerous things and I am not sure if it might apply here. Carlo ``` ## Eric Sunshine, 2023-01-16 01:07 Subject: Re: bugreport: "git checkout -B" allows checking out one branch across multiple worktrees Message-ID: URL: https://gitlist.dev/e/CAPig%2BcQc1%2BD9gH7BAC-r03bGKWx3a9jpPyLuP-ehH-X2P%2BfV6Q%40mail.gmail.com In-Reply-To: <20230116001144.dt76xk6hkwn45klz@Carlos-MacBook-Pro-2.local> ``` On Sun, Jan 15, 2023 at 7:23 PM Carlo Marcelo Arenas Belón wrote: > On Sat, Jan 14, 2023 at 06:45:34PM +0900, Jinwook Jeong wrote: > > 1. `cd` into any git repo that has at least one commit. > > 2. Identify the current branch, say main > > 3. $ git branch foo # a new branch > > 4. $ git worktree add ../new_worktree foo > > 5. $ cd ../new_worktree > > 6. $ git checkout -B master HEAD > > Was your intention to get this worktree's content back to what is in > master's HEAD?, then the command should had been > > $ git reset --hard master > > The documentation might be confusing, but you most likely do NOT want > to use -B unless you want to force things, but the lowercase version `-b` > > > Anything else you want to add: > > > > https://www.git-scm.com/docs/git-checkout#Documentation/git-checkout.txt-emgitcheckoutem-b-Bltnew-branchgtltstart-pointgt > > > > According to the documentation, "git checkout -B BRANCH START" is the > > transactionally equivalent of: > > > > git branch -f BRANCH START > > git checkout BRANCH > > > > When I ran the first command in place of the step 6 of the above > > reproducing procedure, git refused to carry on; > > I suppose that this is the intended behavior for "git checkout -B". > > I think you are correct, and this is therefore a bug, but there is also > a reason why `--force` allows doing dangerous things and I am not sure > if it might apply here. I'd say there's a bug in `git-switch/git-checkout -B` not performing the same checks as `git branch -f`. As a result, it is possible to get into a state in which the same branch is checked out in multiple worktrees, which is probably undesirable. I looked briefly through the code but don't have the time presently to dig into it. ``` ## Jinwook Jeong, 2023-01-16 02:50 Subject: Re: bugreport: "git checkout -B" allows checking out one branch across multiple worktrees Message-ID: URL: https://gitlist.dev/e/CAA3Q-aazO1ko4uBSUs5W_rjn8AP_%3Dfc2jAYrMsaeMtpnm54ExA%40mail.gmail.com In-Reply-To: <20230116001144.dt76xk6hkwn45klz@Carlos-MacBook-Pro-2.local> ``` On Mon, Jan 16, 2023 at 9:11 AM Carlo Marcelo Arenas Belón wrote: > > On Sat, Jan 14, 2023 at 06:45:34PM +0900, Jinwook Jeong wrote: > > What did you do before the bug happened? (Steps to reproduce your issue) > > > > 1. `cd` into any git repo that has at least one commit. > > 2. Identify the current branch, say main > > 3. $ git branch foo # a new branch > > 4. $ git worktree add ../new_worktree foo > > 5. $ cd ../new_worktree > > 6. $ git checkout -B master HEAD > > Was your intention to get this worktree's content back to what is in > master's HEAD?, then the command should had been Sorry for confusion. These steps didn't reflect my real use case but rather are for demonstration. I encountered this issue by chance, not knowing how that command would work under multiple worktrees. ```