Personally, I think an active need and guideline for contributions makes things really nice. If it's easy to clone, get running locally, and run all the tests, then the barrier to entry is lessened for contributing.
Also if you have a history of pleasant, constructive PR comments and history, that is always a good sign of a nice community.
Usually my contributions are need based, and sometimes I've been corrected that it's not within the scope of the project to accept my changes. It really leaves an impression if the owners leave helpful feedback on how to move forward, or explain that it's out of scope.
I totally relate to the "need based" contributions. Thanks for sharing :)
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