Switch CI from bors to merge queue

.github/workflows/main.yml

@@ -1,10 +1,6 @@
 name: CI
 on:
-  push:
-    branches:
-      - auto-cargo
-      - try
-      - automation/bors/try
+  merge_group:
   pull_request:
     branches:
       - "**"
@@ -17,46 +13,39 @@ permissions:
   contents: read
 
 concurrency:
-  group: "${{ github.workflow }}-${{ (github.ref == 'refs/heads/try' && github.sha) || github.ref }}"
+  group: "${{ github.workflow }}-${{ github.ref }}"
   cancel-in-progress: true
 
 jobs:
-  success:
-    permissions:
-      contents: none
-    name: bors build finished
+  conclusion:
     needs:
-    - build_std
-    - clippy
-    - msrv
-    - docs
-    - lockfile
-    - resolver
-    - rustfmt
-    - test
-    - test_gitoxide
-    runs-on: ubuntu-latest
-    if: "success() && github.event_name == 'push' && (github.ref == 'refs/heads/auto-cargo' || github.ref == 'refs/heads/try') && github.repository == 'rust-lang/cargo'"
-    steps:
-    - run: echo ok
-  failure:
+      - build_std
+      - clippy
+      - msrv
+      - docs
+      - lockfile
+      - resolver
+      - rustfmt
+      - test
+      - test_gitoxide
     permissions:
       contents: none
-    name: bors build finished
-    needs:
-    - build_std
-    - clippy
-    - msrv
-    - docs
-    - lockfile
-    - resolver
-    - rustfmt
-    - test
-    - test_gitoxide
+    # We need to ensure this job does *not* get skipped if its dependencies fail,
+    # because a skipped job is considered a success by GitHub. So we have to
+    # overwrite `if:`. We use `!cancelled()` to ensure the job does still not get run
+    # when the workflow is canceled manually.
+    #
+    # ALL THE PREVIOUS JOBS NEED TO BE ADDED TO THE `needs` SECTION OF THIS JOB!
+    if: ${{ !cancelled() }}
     runs-on: ubuntu-latest
-    if: "!success() && github.event_name == 'push' && (github.ref == 'refs/heads/auto-cargo' || github.ref == 'refs/heads/try') && github.repository == 'rust-lang/cargo'"
     steps:
-    - run: exit 1
+      # Manually check the status of all dependencies. `if: failure()` does not work.
+      - name: Conclusion
+        run: |
+          # Print the dependent jobs to see them in the CI log
+          jq -C <<< '${{ toJson(needs) }}'
+          # Check if all jobs that we depend on (in the needs array) were successful.
+          jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'
 
   # Check Code style quickly by running `rustfmt` over all code
   rustfmt: