CI (Buildbot): As soon as a PR is created or updated, create pending (yellow) commit statuses for all Buildbot jobs

.github/CODEOWNERS

@@ -1,3 +1,5 @@
-CODEOWNERS @JuliaLang/github-actions 
-/.github/ @JuliaLang/github-actions 
+CODEOWNERS @JuliaLang/github-actions
+/.github/ @JuliaLang/github-actions
 /.buildkite/ @JuliaLang/github-actions
+
+/.github/workflows/statuses.yml @DilumAluthge

.github/workflows/statuses.yml

@@ -0,0 +1,97 @@
+# Please ping @DilumAluthge when making any changes to this file.
+
+# This is just a short-term solution until we have migrated all of CI to Buildkite.
+#
+# 1. TODO: delete this file once we have migrated all of CI to Buildkite.
+#
+# 2. TODO: disable GitHub Actions on the `JuliaLang/julia` repository once we have migrated all
+# of CI to Buildkite.
+
+# Here are some steps that we take in this workflow file for security reasons:
+# 1. We do not checkout any code.
+# 2. We do not run any external actions.
+
+name: Statuses
+
+on:
+  push:
+    branches:
+      - 'master'
+      - 'release-*'
+  # When using the `pull_request_target` event, all PRs will get a `GITHUB_TOKEN` that has
+  # write permissions, even if the PR is from a fork.
+  # Therefore, for security reasons, we do not checkout any code in this workflow.
+  pull_request:
+    branches:
+      - 'master'
+      - 'release-*'
+
+# These are the permissions for the `GITHUB_TOKEN` token.
+# We should only give the token the minimum necessary set of permissions.
+permissions:
+  statuses:            write
+  actions:             none
+  checks:              none
+  contents:            none
+  deployments:         none
+  issues:              none
+  discussions:         none
+  packages:            none
+  pull-requests:       none
+  repository-projects: none
+  security-events:     none
+
+jobs:
+  statuses:
+    name: statuses
+    runs-on: ubuntu-latest
+    if: github.repository == 'JuliaLang/julia'
+    strategy:
+      fail-fast: false
+    steps:
+      - run: echo "SHA=${{ github.event.pull_request.head.sha }}" >> $GITHUB_ENV
+        if: github.event_name == 'pull_request'
+
+      - run: echo "SHA=${{ env.GITHUB_SHA }}" >> $GITHUB_ENV
+        if: github.event_name != 'pull_request'
+
+      - run: echo "The SHA is ${{ env.SHA }}"
+
+      # As we incrementally migrate individual jobs from Buildbot to Buildkite, we should
+      # remove them from the `context_list`.
+      - run: |
+          declare -a CONTEXT_LIST=(
+                "buildbot/package_freebsd64"
+                "buildbot/package_linux32"
+                "buildbot/package_linuxaarch64"
+                "buildbot/package_linuxarmv7l"
+                "buildbot/package_linuxppc64le"
+                "buildbot/package_macos64"
+                "buildbot/package_macosaarch64"
+                "buildbot/package_musl64"
+                "buildbot/package_win32"
+                "buildbot/package_win64"
+                "buildbot/tester_freebsd64"
+                "buildbot/tester_linux32"
+                "buildbot/tester_linux64"
+                "buildbot/tester_linuxaarch64"
+                "buildbot/tester_linuxarmv7l"
+                "buildbot/tester_linuxppc64le"
+                "buildbot/tester_macos64"
+                "buildbot/tester_macosaarch64"
+                "buildbot/tester_musl64"
+                "buildbot/tester_win32"
+                "buildbot/tester_win64"
+                )
+          for CONTEXT in "${CONTEXT_LIST[@]}"
+          do
+            curl \
+              -X POST \
+              -H "Authorization: token $GITHUB_TOKEN" \
+              -H "Accept: application/vnd.github.v3+json" \
+              -d "{\"context\": \"$CONTEXT\", \"state\": \"$STATE\"}" \
+            https://api.github.com/repos/JuliaLang/julia/statuses/${{ env.SHA }}
+          done
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          STATE: "pending"