build: Increase concurrency, add "basic checks" gatekeeper

.github/workflows/build-syncthing.yaml

@@ -92,6 +92,28 @@ jobs:
         run: |
           go test -v ./meta
 
+  #
+  # The basic checks job is a virtual one that depends on the matrix tests,
+  # the correctness checks, and various builds that we always do. This makes
+  # it easy to have the PR process have a single test as a gatekeeper for
+  # merging, instead of having to add all the matrix tests and update them
+  # each time the version changes. (The top level test is not available for
+  # choosing there, only the matrix "children".)
+  #
+
+  basics:
+    name: Basic checks passed
+    runs-on: ubuntu-latest
+    needs:
+      - build-test
+      - correctness
+      - package-linux
+      - package-cross
+      - package-source
+      - package-debian
+    steps:
+      - uses: actions/checkout@v3
+
   #
   # Windows
   #
@@ -100,8 +122,6 @@ jobs:
     name: Package for Windows
     if: github.event_name == 'push' && (github.ref == 'refs/heads/release' || startsWith(github.ref, 'refs/heads/release-'))
     environment: signing
-    needs:
-      - build-test
     runs-on: windows-latest
     steps:
       - name: Set git to use LF
@@ -157,8 +177,6 @@ jobs:
 
   package-linux:
     name: Package for Linux
-    needs:
-      - build-test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
@@ -199,8 +217,6 @@ jobs:
     name: Package for macOS
     if: github.event_name == 'push' && (github.ref == 'refs/heads/release' || startsWith(github.ref, 'refs/heads/release-'))
     environment: signing
-    needs:
-      - build-test
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v3
@@ -291,6 +307,7 @@ jobs:
     environment: signing
     needs:
       - package-macos
+      - basics
     runs-on: macos-latest
     steps:
       - name: Download artifacts
@@ -320,8 +337,6 @@ jobs:
 
   package-cross:
     name: Package cross compiled
-    needs:
-      - build-test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
@@ -375,8 +390,6 @@ jobs:
 
   package-source:
     name: Package source code
-    needs:
-      - build-test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
@@ -418,6 +431,7 @@ jobs:
     if: github.event_name == 'push' && (github.ref == 'refs/heads/release' || startsWith(github.ref, 'refs/heads/release-'))
     environment: signing
     needs:
+      - basics
       - package-windows
       - package-linux
       - package-macos
@@ -465,8 +479,6 @@ jobs:
 
   package-debian:
     name: Package for Debian
-    needs:
-      - build-test
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3