git subtree: possible to change subtree branch/path in a forked repository?

Question

In a repository A the folder sub is included as git subtree of the repository S - pointing to master branch.

I have forked repository A into F. Now I want to do one of the following in F:

• change sub to use a different branch of S (ie develop branch)
• or: change sub to use a different repository altogether

Is either one of these possible, and if so, how? Will there be any side effects I should know of?

And how can I make sure my subtree change won't be updated in repository A when I merge my changes (pull request)? I mean besides isolating commits.

Solution

If you used git subtree (and not git submodule) to create the subtree, then it's just a normal dir. To switch it to another branch, just delete it and recreate the subtree from the new branch. This is:

git rm <subtree>
git commit
git subtree add --prefix=<subtree> <repository_url> <branch>

That should work without problems.

Comments

[LearnCocos2D]

and that won't be synched upstream? I guess I'll give that a try then.

[elmart]

It won't be synced upstream. The <repository_url> is not saved anywhere; it's just used for the command to know where to get the files from. After that, you get a normal subdir within your repository.

[LearnCocos2D]

Ah ok, I see that now ... subtree simply "copies" the state of a commit of another repository, as if I had copied it manually (but preserving the commit history and what not). So that doesn't change my original problem of not synchronizing a specific folder between two repositories, but sufficiently answers this question.

[Jorge Orpinel Pérez]

Note: I think it's always best to add a remote before adding and pulling a new subtree. In my experience it works much better and can't be done after you add the subtree. See stackoverflow.com/questions/16829401/…

[Skulas]

Since subtree is a folder you need to add -r to recurse it: git rm -r <subtree>