NOTICE: upcoming default branch name change

Nobody has claimed this yet.

The `master` branch of this repository will soon be renamed from `master` to `main`, as part of a coordinated change across the USGS-R and USGS-VIZLAB organizations. This is part of a broader effort across the git community to use more inclusive language. For instance, [git](https://sfconservancy.org/news/2020/jun/23/gitbranchname/), [GitHub](https://github.com/github/renaming), and [GitLab](https://about.gitlab.com/blog/2021/03/10/new-git-default-branch-name/) have all changed or are in the process of changing their default branch name.

We will make this change early in the week of February 6, 2022. The purpose of this issue is to give notification of the change and provide information on how to make it go smoothly.

When this change is made, forks and clones of the repository will need to be updated as well. Here are instructions for making the necessary changes.

- [ ] On GitHub, change the default branch name from `master` to `main` (\ -> Settings -> Branches).
- [ ] Change the default branch on any forks you have, as well as local clones. (See details below)
- [ ] If you have collaborators on this repository, let them know that they will need to change their forked/local repos. Point them to this issue to facilitate the process!
- [ ] Search within your repository for "master" so that you can change references (e.g. URLs pointing to specific commit points of files) to point to "main" instead.
- [ ] When you are done, feel free to close this issue!

### Changing default branches on forks and local clones
First, update your local git configuration so that new repositories created locally will have the correct default branch: `git config --global init.defaultBranch main`.

Now, for any forks, do the following:
1. Go to \ -> Settings -> Branches and edit the default branch from `master` to `main`.
1. Update the settings for your local clone of this fork to match this change.

```r
git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a
```

Review the repository's GitHub default-branch setting and search the repository for references to "master". Follow the listed fork and local-clone commands to verify the migration guidance, then update any references that still point to the old branch and close the issue when the change is complete.

Written by the indexing model from the issue text.