Pre-merge testing enabled by default

Dear LLVM community,

After 3 months of beta testing [4] and a lot of feedback from you, we just enabled the pre-merge tests [1] for all LLVM Revisions on Phabricator.

The pre-merge tests will just point out things that might be breaking related to your change, they are not blocking you from landing your changes or slowing you down in any way. In case you still want to opt-out, you can add yourself to the project [2]. Please also let us know why you’re opting out, so we might be able to address the issue in the future [3].

The current features and usage are explained in [1]. If you find a bug, please raise an issue at [3]. If you’re interested in contributing, please reach out.

[1] https://github.com/google/llvm-premerge-checks/blob/master/docs/user_doc.md
[2] https://reviews.llvm.org/project/members/83/
[3] https://github.com/google/llvm-premerge-checks/issues
[4] http://lists.llvm.org/pipermail/llvm-dev/2019-November/137195.html

Best,
Christian and Mikhail

This is really fantastic Christian! Thank you!

-Chris