add comments to explain cache behavior

.github/workflows/reusable-unit-tests.yml

@@ -59,12 +59,15 @@ jobs:
         with:
           fetch-depth: 0
 
-      # skip the "cache: maven" step from setup-jave since we restore it below
+      # skip the "cache: maven" step from setup-java. We explicitly use a
+      # different cache key since we cannot reuse it across commits.
       - uses: actions/setup-java@v3
         with:
           distribution: 'zulu'
           java-version: ${{ inputs.jdk }}
 
+      # the build step produces SNAPSHOT artifacts into the local maven repository,
+      # we include github.sha in the cache key to make it specific to that build/jdk
       - name: Restore Maven repository
         id: maven-restore
         uses: actions/cache/restore@v3

.github/workflows/standard-its.yml

@@ -153,6 +153,8 @@ jobs:
       - name: Setup java
         run: export JAVA_HOME=$JAVA_HOME_8_X64
 
+      # the build step produces SNAPSHOT artifacts into the local maven repository,
+      # we include github.sha in the cache key to make it specific to that build/jdk
       - name: Restore Maven repository
         id: maven-restore
         uses: actions/cache/restore@v3

.github/workflows/unit-and-integration-tests-unified.yml

@@ -62,11 +62,15 @@ jobs:
       - name: Checkout branch
         uses: actions/checkout@v3
 
+      # skip the "cache: maven" step from setup-java. We explicitly use a
+      # different cache key since we cannot reuse it across commits.
       - uses: actions/setup-java@v3
         with:
           distribution: 'zulu'
           java-version: ${{ matrix.jdk }}
 
+      # the build step produces SNAPSHOT artifacts into the local maven repository,
+      # we include github.sha in the cache key to make it specific to that build/jdk
       - name: Cache Maven m2 repository
         id: maven
         uses: actions/cache@v3