Renaming Cantera's default branch

There has been a growing awareness that the use of the name master for the default branch in Git repositories perpetuates the use of the language of oppression. It has also been shown that the use of the term master in Git likely does stem from the harmful master/slave metaphor, which it inherited from an earlier piece of software.

With the aim of upholding our commitment to fostering an open and welcoming environment as outlined in our Code of Conduct, specifically the standard of using welcoming and inclusive language, we have changed the default branch name in Cantera to main, and recommend this change to others for their forks and local repositories as well.

Adapting to this change will require a few small changes for anyone who has already checked out a copy of the Cantera source code using Git, and instructions which should help in most cases are provided below.

Updating your local repository and GitHub fork

To change the name of Cantera's default branch open a shell, navigate to the Cantera source directory, and run the following commands:

$ git fetch --all
$ git checkout master
$ git branch -m master main
$ git status
On branch main
Your branch is up to date with 'origin/master'.

If your master branch isn't up to date with its upstream, you will want to fix that first using your preferred workflow to synchronize the two branches. If you have made any local changes to the master branch, you should create a feature branch to avoid losing any changes.

Next, we want to update the link between your main branch and the remote repository (here, origin). You can check whether this remote is the main Cantera repository or your fork on GitHub (or a different source) by running the command:

$ git remote --verbose
origin (fetch)
origin (push)
myfork (fetch)
myfork (push)
Case 1: tracked remote is Cantera/cantera

If the remote being tracked (in this example, origin) is the main Cantera repository, that is, Cantera/cantera.git, then you can set the main branch of Cantera/cantera as the upstream for your main branch:

$ git branch --unset-upstream
$ git branch -u origin/main
$ git fetch
$ git rebase origin/main

Then, you can push the updated main branch to your fork (in this example, myfork) as well:

$ git push main myfork
Case 2: tracked remote is your fork

If the remote listed is your fork of Cantera, then you may want to rename the branch on your fork as well. If the remote name for your fork is myfork, this can be changed by running:

$ git push -u myfork main

Deleting the old branch from your fork

Once you have pushed the new main branch to your fork, visit the GitHub website for your fork, go to Settings, then Branches, then Default Branch, and set the default branch to main.

Once you make sure that the main branch shows any recent commits that you expect to see, you can delete the old branch from your fork:

$ git push origin --delete master

If you get an error message that says

! [remote rejected]     master (refusing to delete the current branch: refs/heads/master)`

this suggests that you haven't successfully changed the default branch on GitHub.