mugit repo new desc-repo

mugit repo description desc-repo
stderr 'description=""' # fix output

mugit repo description desc-repo 'new test desc'
stderr 'new_description="new test desc"' # fix output

mugit repo description desc-repo
stderr 'new_description="new test desc"' # fix output

# missing repo name
! mugit repo description
stderr 'no name provided'

# repo does not exist
! mugit repo description nonexistent
stderr 'failed to open repo'