Allow initializing a repository with a branch name other than `master`

Hi,
thanks for your work.

It looks like one can only switch to another branch (e.g. `main`) as the default branch once the repository has been created. Using `main` as the default branch name is increasingly common/even the default choice for many code/data hosting repositories. Can you please provide the option to name the default branch to any name other than `master` please?

Thank you.

No files, tests, or entry points are named. Locate the repository initialization and default-branch handling, then trace how the initial branch name is chosen. Done means initialization accepts a chosen branch name such as main instead of always using master.

Written by the indexing model from the issue text.