`--variable` is used frequently enough to deserve a shorthand. Unfortunately,
`-v` is taken by verbose, and `-V` is too easily confused with version or
verbose, so we're left with "--var".
So that we can push template updates for testing without impacting
normal users of the template.
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Co-authored-by: Ammar Bandukwala <ammar@ammar.io>
Co-authored-by: Muhammad Atif Ali <matifali@live.com>
Co-authored-by: Atif Ali <atif@coder.com>