[chore] Do not cancel build-and-test workflows on main (#16616)

According to github documentation here: https://docs.github.com/en/enterprise-cloud@latest/actions/using-jobs/using-concurrency#example-using-a-fallback-value,

"The following concurrency group cancels in-progress jobs or runs on pull_request events only; if github.head_ref is undefined, the concurrency group will fallback to the run ID, which is guaranteed to be both unique and defined for the run."

Effectively, workflows with this configuration will be cancelled when changes are pushed to a PR, but not when a PR is merged to main.

I've applied this change to two specific workflows:
- build-and-test: Because this is the workflow that populates the repo's status badge. When this workflow is canceled, the badge shows a failure.
- build-and-test-windows: A recent decision was made to run this only on main. We should ensure that it actually does run on main for each PR.

.github/workflows/build-and-test-windows.yml

@@ -16,8 +16,9 @@ env:
  # Cache downloads for this workflow consistently run in under 10 minutes
  SEGMENT_DOWNLOAD_TIMEOUT_MINS: 15
 
+# Do not cancel this workflow on main
 concurrency:
- group: ${{ github.workflow }}-${{ github.head_ref }}
+ group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
  cancel-in-progress: true
 
 jobs:
@@ -61,7 +62,7 @@ jobs:
  ~\AppData\Local\go-build
  key: go-build-cache-${{ runner.os }}-${{ matrix.group }}-go-${{ hashFiles('**/go.sum') }}
  - name: Run Unit tests
- run: make -j2 gotest GROUP=${{ matrix.group }} 
+ run: make -j2 gotest GROUP=${{ matrix.group }}
  - name: Analyze Test and/or Coverage Results
  if: always()
  uses: runforesight/foresight-test-kit-action@v1

.github/workflows/build-and-test.yml

@@ -11,9 +11,10 @@ env:
  # Cache downloads for this workflow consistently run in under 1 minute
  SEGMENT_DOWNLOAD_TIMEOUT_MINS: 5
 
+# Do not cancel this workflow on main. See https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/16616
 concurrency:
- group: ${{ github.workflow }}-${{ github.head_ref }}
- cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+ group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+ cancel-in-progress: true
 
 jobs:
  setup-environment: