fix(ci): sweep and inject GHA fallback SHAs inside all client library workflows

Author: meltsufin

.github/workflows/java-bigtable-ci.yaml

@@ -137,8 +137,8 @@ jobs:
     - run: .kokoro/build.sh
       env:
         JOB_TYPE: lint
-        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
-        BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.before }}
   clirr:
     needs: filter
     if: ${{ needs.filter.outputs.library == 'true' }}

.github/workflows/java-pubsub-ci.yaml

@@ -137,8 +137,8 @@ jobs:
     - run: .kokoro/build.sh
       env:
         JOB_TYPE: lint
-        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
-        BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.before }}
   clirr:
     needs: filter
     if: ${{ needs.filter.outputs.library == 'true' }}

.github/workflows/java-spanner-jdbc-ci.yaml

@@ -141,8 +141,8 @@ jobs:
     - run: .kokoro/build.sh
       env:
         JOB_TYPE: lint
-        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
-        BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.before }}
   required:
     needs: [ units, units-java8, windows, dependencies, javadoc, lint ]
     name: conditional-required-check

.github/workflows/java-storage-nio-ci.yaml

@@ -141,8 +141,8 @@ jobs:
     - run: .kokoro/build.sh
       env:
         JOB_TYPE: lint
-        HEAD_SHA: ${{ github.event.pull_request.head.sha }}
-        BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.before }}
   required:
     needs: [ units, units-java8, windows, dependencies, javadoc, lint ]
     name: conditional-required-check