The stack upgrade command

Either:

stack upgrade [--binary-only] [--binary-platform ARG] [--force-download]
              [--binary-version ARG] [--github-org ARG] [--github-repo ARG]

or:

stack upgrade [--source-only] [--git] [--git-repo ARG] [--git-branch ARG]

stack upgrade will get a new version of Stack, either from an existing binary distribution (pass the --binary-only flag, the default) or from compiling source code (pass the --source-only flag). The --binary-only and --source-only flags are alternatives.

--git is a convenient way to get the most recent version from the master branch, for those testing and living on the bleeding edge.