Specify branch for retrieving snakemake repository #21
Description
Currently, the git clone ... command in the projects.py file retrieves a single branch, but it's always the default. Adding a -b {branchname} option there, and a config value to set it, could add some flexibility. Adding an issue here because I know I'm going to forget to account for the fact that if the user doesn't specify a branch, we don't know if it should be main or master or something else by default, so if branchname is unset, we shouldn't include that option at all.