Most engineers are familiar with creating branches and making commits in Git. The tool is notoriously unintuitive but has become universal in software engineering. But did you know that you can store more than just snapshots of code?

There is already a long history of tools hacking small amounts of metadata into Git. For example, the open-source code review tool Gerrit ingests pull requests through git push by allowing the user to encode data in the name of the remote ref. …


The standard workflow in git is to create feature branches off of a trunk branch (usually called main), submit a pull request, and merge approved changes back into the trunk. This is fairly straightforward and follows the patterns of most pre-git version control systems. However, as any experienced developer can tell you, this workflow is not without issues. One of the biggest challenges of the feature branch workflow is that it often induces developers to create massive pull requests once they've finished building. If you're working on a large project over many weeks or months, your feature branch can easily…


TL;DR:

Using the command

arch -arm64 /Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild ...

We were able to run XCUITests on Mac Silicon machines controlled by GitHub Actions self-hosted runners.

  • arch -x86_64 boots GitHub’s self-hosted runner software.
  • arch -arm64 checks if you’re on an M1 mac and also escapes emulation inheritance.
  • We found both arm64 and arm64e architecture of xcodebuild on our machines.

Full story

Screenplay’s continuous integration (CI) tests take about 120 minutes of Mac compute to test our software against 10+ major open-source apps. I wanted to add compacity to the CI worker cluster, so I ambitiously purchased two ARM Mac Minis.

I used Migration Assistant…


For ten years, the computer science research community has attempted to develop a practical smartphone-based indoor localization system. While GPS allows users to navigate streets and cities easily, it fails to accurately localize a user within a room of a building. In this independent research project, I expand on current Magnetic Localization research and demonstrate the accuracy achievable by applying real-time Particle Filtering on magnetic magnitude readings from an iPhone 7 Plus. I also explore the novel and practical idea of measuring the magnetic distributions for rooms in order to perform room identification. …

Greg Foster

Screenplay Cofounder, Former Airbnb Software Engineer, Harvard CS ‘17

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