Prepare for a v1 release

[korthout]

This action has been around for some time now and is actively used by multiple large and very active projects. It has been tested in production for long enough. It's time to remove the This project is still in an early development stage note at the top of the README and release v1 of the backport action.

What should be included in v1?

IMO, a v1 release should come with a major feature or large change to the project. The main feature of the v1 release of the backport action might as well be performance (or energy efficiency). While investigating a performance regression, we researched how to use shallow clones and fetch-depth to optimize the git clone (via actions/checkout), and the git fetches to the bare minimum. These lead to small improvements for small projects and should lead to large improvements for repositories with a long history. This performance improvement is not yet production ready, but we could easily turn it into a release candidate which we can battle-test before releasing v1.

I started this project originally together with @pihme to solve a specific problem for the Zeebe team: to automatically backport pull requests merged with octopus commits. Over time, the action has also found usages outside of Camunda. To improve the visibility, I'd like to publish the action on the GitHub Marketplace. Therefore, I will move this repo under my personal account github.com/korthout. There, I will be able to take more control over the project and work towards releasing it more often.

Checklist

• clean up the code from korthout-fetch-depth Optimize git fetch-depth #296
• create a release candidate v1-rc1
• update the README to announce release candidate and repo ownership move
• battle test for one month, releasing more candidates if needed, e.g. v1-rc2
• move repo to personal account after battle testing is completed
• rename master to main
• remove the memo from the README
• release v1, v1.0, and v1.0.0 (switch to full semantic versioning after this)
• publish to marketplace