Fix: normalize _remote.repositories repo ID for offline mode (#1393)

## Summary
Deleting _remote.repositories was not enough — Maven 3.9+ still refused
cached artifacts in offline mode with "has not been downloaded from it
before". The root cause: Maven checks that the artifact was downloaded
from "central" but the _remote.repositories files referenced
"jfrog-central" (the warmer mirror ID).

Fix: in the warmer, sed-replace "jfrog-central" with "central" in all
_remote.repositories files before saving the cache. This makes Maven
offline mode accept cached artifacts as coming from "central" (the
default repo ID).

Verified locally: ALL 5 CI commands pass with replaced repo IDs +
offline mode:
- spotless:check → BUILD SUCCESS
- unit tests → BUILD SUCCESS
- jacoco:report → BUILD SUCCESS
- packaging install → BUILD SUCCESS
- test-compile → BUILD SUCCESS

## After merge
1. Delete stale cache entries
2. Trigger cache warmer
3. Re-run PR #1371 CI

NO_CHANGELOG=true

This pull request was AI-assisted by Isaac.

---------

Signed-off-by: Gopal Lal <gopal.lal@databricks.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: gopalldb

.github/actions/setup-maven/action.yml

@@ -27,18 +27,10 @@ runs:
       run: |
         mkdir -p ~/.m2
 
-        # Remove _remote.repositories marker files. These track which remote
-        # repo each artifact came from. Without them, Maven treats all cached
-        # artifacts as locally installed and resolves them without contacting
-        # any remote server.
-        find ~/.m2/repository -name '_remote.repositories' -delete 2>/dev/null || true
-        echo "Removed _remote.repositories markers from cache"
-
-        # Enable Maven offline mode via .mvn/maven.config. This file is read
-        # automatically by Maven as default CLI arguments. Offline mode prevents
+        # Enable Maven offline mode via .mvn/maven.config. Offline mode prevents
         # all network requests — no JFrog auth needed, no Maven Central fallback.
-        # Combined with _remote.repositories removal, Maven resolves everything
-        # from the local cache.
+        # The cache warmer normalizes _remote.repositories to use 'central' as the
+        # repo ID, so offline mode accepts all cached artifacts.
         mkdir -p .mvn
         echo "-o" >> .mvn/maven.config
         echo "Maven offline mode enabled via .mvn/maven.config"
@@ -48,7 +40,7 @@ runs:
         <settings />
         SETTINGS_EOF
 
-        echo "Maven configured for forked PR (cache-only, no remote access)"
+        echo "Maven configured for forked PR (offline mode, cache-only)"
 
     # --- Same-repo path: full JFrog OIDC authentication ---
     - name: Get JFrog OIDC token

.github/workflows/warmMavenCache.yml

@@ -160,15 +160,18 @@ jobs:
 
           echo "Dependency resolution complete"
 
-      - name: Remove _remote.repositories before saving cache
+      - name: Normalize _remote.repositories before saving cache
         shell: bash
         run: |
-          # Remove _remote.repositories marker files before saving. These track
-          # which remote repo ID each artifact was downloaded from (jfrog-central).
-          # Without them, forked PRs can use the cache in offline mode without
-          # Maven complaining about repo ID mismatches.
-          COUNT=$(find ~/.m2/repository -name '_remote.repositories' -delete -print | wc -l)
-          echo "Removed ${COUNT} _remote.repositories markers"
+          # Replace 'jfrog-central' with 'central' in _remote.repositories files.
+          # These files track which repo ID each artifact was downloaded from. The
+          # cache warmer downloads from 'jfrog-central' (the JFrog mirror), but
+          # Maven's offline mode expects artifacts to be associated with 'central'
+          # (the default Maven Central repo ID). Without this, offline mode refuses
+          # cached artifacts with "has not been downloaded from it before".
+          COUNT=$(find ~/.m2/repository -name '_remote.repositories' -print | wc -l)
+          find ~/.m2/repository -name '_remote.repositories' -exec sed -i 's/jfrog-central/central/g' {} \;
+          echo "Normalized ${COUNT} _remote.repositories markers (jfrog-central -> central)"
 
       - name: Save Maven dependency cache
         uses: actions/cache/save@0057852bfaa89a56745cba8c7296529d2fc39830 # v4