KAFKA-18500 Build PRs at HEAD commit

.github/workflows/README.md

@@ -133,4 +133,47 @@ Composite actions are a convenient way to reuse build logic, but they have
 some limitations. 
 
 - Cannot run more than one step in a composite action (see `workflow_call` instead)
-- Inputs can only be strings, no support for typed parameters. See: https://github.com/actions/runner/issues/2238
+- Inputs can only be strings, no support for typed parameters. See: https://github.com/actions/runner/issues/2238
+
+## Troubleshooting
+
+### Gradle Cache Misses
+
+If your PR is running for longer than you would expect due to cache misses, there are a
+few things to check. 
+
+First, find the cache that was loaded into your PR build. This is found in the Setup Gradle
+output. Look for a line starting with "Restored Gradle User Home from cache key". 
+For example,
+
+```
+Restored Gradle User Home from cache key: gradle-home-v1|Linux-X64|test[188616818c9a3165053ef8704c27b28e]-5c20aa187aa8f51af4270d7d1b0db4963b0cd10b
+```
+
+The last part of the cache key is the SHA of the commit on trunk where the cache
+was created. If that commit is not on your branch, it means your build loaded a 
+cache that includes changes your PR does not yet have. This is a common way to
+have cache misses. To resolve this, update your PR with the latest cached trunk commit:
+
+```commandline
+git fetch origin
+./committer-tools/update-cache.sh
+git merge trunk-cached
+```
+
+then push your branch.
+
+If your build seems to be using the correct cache, the next thing to check is for
+changes to task inputs. You can find this by locating the trunk Build Scan from 
+the cache commit on trunk and comparing it with the build scan of your PR build.
+This is done in the Develocity UI using the two overlapping circles like `(A()B)`. 
+This will show you differences in the task inputs for the two builds.
+
+Finally, you can run your PR with extra cache debugging. Add this to the gradle invocation in
+[run-gradle/action.yml](../actions/run-gradle/action.yml). 
+
+```
+-Dorg.gradle.caching.debug=true
+```
+
+This will dump out a lot of output, so you may also reduce the test target to one module.

.github/workflows/build.yml

@@ -36,7 +36,8 @@ jobs:
     name: Configure Workflow
     outputs:
       is-draft: ${{ steps.check-draft-pr.outputs.is-draft }}
-      test-catalog-days: ${{ steps.test-catalog.outputs.days }}
+      test-catalog-days: ${{ steps.configure-outputs.outputs.days }}
+      sha: ${{ steps.configure-outputs.outputs.sha }}
     steps:
       - name: Env
         run: printenv
@@ -48,13 +49,15 @@ jobs:
           github.event_name == 'pull_request' && 
           github.event.pull_request.draft
         run: echo "is-draft=true" >> "$GITHUB_OUTPUT"
-      - name: Test Catalog Age
-        id: test-catalog
+      - name: Configure Outputs
+        id: configure-outputs
         run: |
           if [ "${{ github.event_name }}" = "pull_request" ]; then
             echo "days=0" >> "$GITHUB_OUTPUT"
+            echo "sha=${{ github.event.pull_request.head.sha }}" >> "$GITHUB_OUTPUT"
           else
             echo "days=7" >> "$GITHUB_OUTPUT"
+            echo "sha=${{ github.sha }}" >> "$GITHUB_OUTPUT"
           fi
 
   load-catalog:
@@ -108,7 +111,7 @@ jobs:
   validate:
     needs: [configure]
     runs-on: ubuntu-latest
-    name: Compile and Check Java
+    name: Compile and Check (Merge Ref)
     steps:
       - name: Env
         run: printenv
@@ -118,6 +121,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           persist-credentials: false
+          ref: ${{ github.sha }}  # this is the default, just being explicit.
       - name: Setup Python
         uses: ./.github/actions/setup-python
       - name: Setup Gradle
@@ -189,6 +193,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           persist-credentials: false
+          ref: ${{ needs.configure.outputs.sha }}
       - name: Setup Python
         uses: ./.github/actions/setup-python
       - name: Setup Gradle