ci: Switch from bors to merge queues

The success job is copied from how rust-lang/miri-test-libstd does it.

.github/workflows/ci.yaml

@@ -1,9 +1,5 @@
 name: CI
-on:
-  push:
-    branches:
-      - staging
-      - trying
+on: merge_group
 
 jobs:
 
@@ -48,3 +44,18 @@ jobs:
         with:
           components: rustfmt
       - run: cargo fmt --all --check
+
+  # One job that "summarizes" the success state of this pipeline. This can then be added to branch
+  # protection, rather than having to add each job separately.
+  success:
+    name: Success
+    runs-on: ubuntu-latest
+    needs: [test, no_std, fmt]
+    # Github branch protection is exceedingly silly and treats "jobs skipped because a dependency
+    # failed" as success. So we have to do some contortions to ensure the job fails if any of its
+    # dependencies fails.
+    if: always() # make sure this is never "skipped"
+    steps:
+      # Manually check the status of all dependencies. `if: failure()` does not work.
+      - name: check if any dependency failed
+        run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'

.github/workflows/pr.yaml

@@ -27,3 +27,18 @@ jobs:
         with:
           components: rustfmt
       - run: cargo fmt --all --check
+
+  # One job that "summarizes" the success state of this pipeline. This can then be added to branch
+  # protection, rather than having to add each job separately.
+  success:
+    name: Success
+    runs-on: ubuntu-latest
+    needs: [test, fmt]
+    # Github branch protection is exceedingly silly and treats "jobs skipped because a dependency
+    # failed" as success. So we have to do some contortions to ensure the job fails if any of its
+    # dependencies fails.
+    if: always() # make sure this is never "skipped"
+    steps:
+      # Manually check the status of all dependencies. `if: failure()` does not work.
+      - name: check if any dependency failed
+        run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'

Cargo.toml

@@ -10,7 +10,7 @@ name = "num-complex"
 repository = "https://github.com/rust-num/num-complex"
 version = "0.4.4"
 readme = "README.md"
-exclude = ["/bors.toml", "/ci/*", "/.github/*"]
+exclude = ["/ci/*", "/.github/*"]
 edition = "2018"
 
 [package.metadata.docs.rs]