What tools do you use for your open source projects?

I use Travis CI for automated builds because it's easy to set up and I don't have to know much about the CI infrastructure, like on many other platforms. But they do tend to have stability issues, and I'd really love to test my projects on a windows environment, which they don't support. I use Appveyor for testing on windows, but I really wish I could find a hosted CI tool that supports windows, Mac, and Linux all together, and integrates well with github.

Codacy is my preferred tool for tracking code coverage, because it checks code coverage and code style all together.

Gradle is my go-to build tool, and though I don't do much front-end web dev, I would choose it over a pure webpack or gulp build anyday. The kotlin folks have a Gradle plugin for managing webpack (for Kotlin/JS), so that will be my preferred way to do it, next time I start a front-end project.

For managing documentation, I use my own framework Orchid, which brings together the projects wiki, code API docs, and standalone pages all into one build tool, and which automatically deploys to github pages or Netlify.

If you can't tell by now, I really like having a few good tools that do lots of things well, rather than having a new tool for every job.😉 Fewer tools might give me less flexibility overall, but it's easier for me to manage and it's usually easier for the integrations to work together more efficiently.

I use Travis CI, VSTS, SonarCloud and prettier.

I have only used Travis CI.
Its pretty good for my node / typescript project.

I use a very simple setup for my current project. It's written in C so I just use gcc for building it, atom as my code editor, and Trello for keeping notes.