[llvm] [GitHub] Allow shortcut for "introductory issue" and request linking to issue in PR (PR #84635)

[Simon Pilgrim via llvm-commits]

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@@ -24,12 +24,13 @@
 
 This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:
 
-1. In the comments of the issue, request for it to be assigned to you.
-2. Fix the issue locally.
-3. [Run the test suite](https://llvm.org/docs/TestingGuide.html#unit-and-regression-tests) locally. Remember that the subdirectories under `test/` create fine-grained testing targets, so you can e.g. use `make check-clang-ast` to only run Clang's AST tests.
-4. Create a Git commit.
-5. Run [`git clang-format HEAD~1`](https://clang.llvm.org/docs/ClangFormat.html#git-integration) to format your changes.
-6. Open a [pull request](https://github.com/llvm/llvm-project/pulls) to the [upstream repository](https://github.com/llvm/llvm-project) on GitHub. Detailed instructions can be found [in GitHub's documentation](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request).
+1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
+1. In the comments of this issue, request for it to be assigned to you, or just create a [pull request](https://github.com/llvm/llvm-project/pulls) after following the steps below. [Mention](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue) this issue in the description of the pull request.
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RKSimon wrote:

Should we explicitly say that raising a PR for an issue assigned to somebody else might lead to your PR being rejected? We should perhaps get some advice from other people on this as we're creating policy here.

https://github.com/llvm/llvm-project/pull/84635