Add MIRROR Jinja2 variable in rose-stem and associated test
Implement Matt's tidier suggestion
rose date: fix --calendar=365day|366day option

Option documented but not implemented correctly.
Merge pull request #1463 from matthewrmshin/rose-date-365-366

rose date: fix --calendar=365day|366day option
Merge pull request #1461 from scwhitehouse/mirror_var

Add MIRROR Jinja2 variable in rose-stem and associated test