I'm going to work on a Shopify theme, and I want to figure out how to run/edit it locally. I'd like to be able to the following, if possible:
Is this at all possible?
There are quite a few workflows you can use here.
Slate is a theme scaffold and command line tool for developing Shopify themes. It is designed to assist your development workflow and speed up the process of developing, testing, and deploying themes to Shopify stores.
This is the new way for developing themes that the Shopify team has been working on for a while and soft launched publically around the 23rd of March 2017. Seems to be nowadays the most complete and proficient way of working with Shopify.
https://github.com/Shopify/slate
If you're using either Gulp or Grunt locally for development, there are libraries out there that will upload your files to the store through API credentials of a Private App that you have to create. Most work by uploading the files you change, using a watcher.
Theme Kit is a cross-platform CLI tool that was built by Shopify Employees. It can run on windows/linux/OS X. You can read more about it on Shopify Blog or download it directly. The alternative previously mentioned of Desktop Theme Editor is deprecated and has been replaced by Theme Kit.
Instead of watching for changes, these will work with a continuos integration workflow, where your latest push on a certain branch gets uploaded to the theme you've selected.
There's an unofficial extended cli similar to theme kit but with further functionality called Quickshot, which I've just found out based on Matt's response and seems pretty awesome. Some of the features they highlight are: