• How does this affect you:

Very little. When creating a pull request through the GitHub web UI, GitHub will compare your branch with the upstream 'main' branch by default from now on (instead of comparing with the 'master' branch). The 'master' branch will be eventually deleted assuming this migration goes well. In the meanwhile, I promise to keep my eyes peeled and always double-check any pull request opened gets merged to the 'main' branch of sparklyr, rather than the 'master' branch.

Reason 1: the default branch being named 'main' rather than 'master' is currently the default convention on GitHub, and in near future it will be the norm rather than the exception. It's best we conform to this convention sooner rather than later.

Reason 2: there is no open pull request or ongoing release for sparklyr at the moment, so, performing this migration now would cause little to no disruption.

In my opinion https://github.com/github/renaming did a pretty good job documenting all aspects of this renaming process. 

I believe it will be safe to delete the old 'master' branch of sparklyr later this year after the automatic redirection from 'master' to 'main' is happening seamlessly everywhere on github.com (including, say, for use cases such as `remote::install_github("sparklyr/sparklyr", ref = "master")` which I'm aware is the modus operandi for some advanced users).