Use of git worktree to handle git ignored node_modules/ of two existing branches or move to a different approach

Question

I have a repo with two branches, and I don't know how to handle the git ignored node_modules folder that should contain different packages in the two branches. From my understanding, git-worktree is the correct approach, but I can't figure out how to use it.

Because the two branches already have many commits, I need a solution that preserve all of them.

At the moment, every time a checkout, I run:

rm -r node_modules
npm install

But because this process is not convenient, I investigated, and it looks that the suggested solution is to use git worktree. Somewhere else, it doesn't seam the correct approach.

If it is the correct approach, I can't figure out how to use it in practice.

If I run:

git worktree add ./node_modules <current_branch_name>

I get:

fatal: '<current_branch_name>' is already checked out at '/some/path/my-project-folder'

If I run

git worktree add ./node_modules <other_branch_name>

The folder is created, but running npm install the packages are installed in it, making it unusable when I switch branch with git checkout <other_branch_name>.

If I create two folders with:

git worktree add ./node_modules_foo <current_branch_name>
git worktree add ./node_modules_bar <other_branch_name>

They are created, but not used by npm install unless I move the package.json files in them, that is not what I want and could be done also without git worktree.

Is it git worktree the correct approach for this problem and how to use it correctly?

I also investigate another approach, to specify a different installation folder in the package.json file, but it looks it is not an option.

Answer 1

Going by what the linked article said:

Use directory ../branch1 to work on branch branch1:

git worktree add ../branch1 branch1

So a sibling directory.

Then likewise for branch2:

git worktree add ../branch2 branch2

But the article is wrong about this though:

Whenever you run git checkout my-feature-branch, it'll automatically switch to that folder.

No. The worktrees are checked out at those branches, and you cannot change those branches in the current worktree; you will have to do cd ../branch1 to “check out” branch1 and likewise for branch2. (If you try git checkout branch1 you will get a fatal error, since you have checked out branch1 in another worktree; you will not automatically change the directory to ../branch1.)

I guess the idea here is to “freeze” a branch on each worktree so that you don’t have to blow away that node_modules bloat on every branch change.

Just do:

cd ../branch1
npm install

And:

cd ../branch2
npm install

And then change directory back to whichever when you need to work on them again; node_modules (if it is untracked, anyway) won’t have been disturbed so there won’t be a need to rm -r node_modules.

At least that’s what I think the article is about.