Describe the feature or problem you’d like to solve

Currently, when calling gh gist edit, it triggers the OS to open the default editor.

A clear and concise description of what the feature or problem is.

Most editors require manual intervention, making it where updating an existing file in a gist, programmatically, is difficult and/or tedious.

Proposed solution

gh gist update -s <local_file> -d <gist_file> -m <commit_message>

How will it benefit CLI and its users?

This could mimic functionality found in a competitor.
Each repo has a "Downloads" section w/ BitBucket.
Overwriting an existing file in the Downloads folder is just a curl/requests POST away, but no such functionality exists w/ gists.

Additional context

Add any other context like screenshots or mockups are helpful, if applicable.