I want to add a pkg-message to py-robot-detection, but I'm not confident of the workflow to use git arc to fetch the latest revision, make changes and update it again.

This is the text, taken from https://github.com/amandasaurus/robot-detection, modified to use fetch instead of wget:

You can download a new version of the Robot Database from http://www.robotstxt.org/dbexport.html.

Download the database dump, and run the file robot_detection.py with the file as first argument.

	$ fetch http://www.robotstxt.org/db/all.txt
	$ python robot_detection.py all.txt

If the database has changed, it'll print out the new version of robot_useragents variable that you need to put into the source code.

In D52550#1200850, @einar_isnic.is wrote:

I want to add a pkg-message to py-robot-detection, but I'm not confident of the workflow to use git arc to fetch the latest revision, make changes and update it again.

It's actually very simple. That's why I like to use Phabricator more than Bugzilla:

To fetch the latest revision:
arc patch 52550
To update it again:
arc diff --update 52550