fix: simplify git strategy to use 'git show HEAD' for maintenance branches

- Remove complex HEAD~1..HEAD logic that fails in shallow clones
- Use simple 'git show --name-only HEAD' for maintenance branches
- Fix output parsing to properly extract module names
- Improve verbose logging to show actual strategy used

This approach is much simpler and more reliable:
- No dependency on git history depth
- Cherry-pick commits contain the files that changed
- Works consistently in GitHub Actions environment

Author: markpollack

.github/scripts/test_discovery.py

@@ -62,20 +62,10 @@ def _get_changed_files(self, base_ref: Optional[str] = None) -> List[str]:
             pr_head = os.environ.get('GITHUB_HEAD_HEAD')   # PRs  
             branch = os.environ.get('GITHUB_REF_NAME')    # pushes
 
-            # For maintenance branches (cherry-picks), always use single commit diff
+            # For maintenance branches (cherry-picks), get files from the commit itself
             if branch and branch.endswith('.x'):
-                # Maintenance branch - cherry-picks are always single commits
-                # Try HEAD~1..HEAD first, fallback to different strategies if not available
-                try:
-                    # Test if HEAD~1 exists
-                    subprocess.run(["git", "rev-parse", "HEAD~1"], 
-                                 cwd=self.repo_root, check=True, capture_output=True)
-                    cmd = ["git", "diff", "--name-only", "HEAD~1..HEAD"]
-                except subprocess.CalledProcessError:
-                    # HEAD~1 not available (shallow clone), try other approaches
-                    print("HEAD~1 not available, trying alternative approaches", file=sys.stderr)
-                    # Try showing just the files in the current commit
-                    cmd = ["git", "show", "--name-only", "--format=", "HEAD"]
+                # Maintenance branch - cherry-picks are single commits, just get files in this commit
+                cmd = ["git", "show", "--name-only", "--format=", "HEAD"]
             elif base_ref:
                 # Explicit base reference provided - use two-dot diff for direct comparison
                 cmd = ["git", "diff", "--name-only", f"{base_ref}..HEAD"]
@@ -190,7 +180,7 @@ def _detect_default_base(self) -> str:
 
         # Show the actual strategy being used
         if branch and branch.endswith('.x'):
-            return f"HEAD~1 (single commit - maintenance branch {branch})"
+            return f"git show HEAD (maintenance branch {branch})"
         elif pr_base:
             return f"origin/{pr_base} (PR base)"
         elif branch:

.github/workflows/maintenance-fast.yml

@@ -76,8 +76,12 @@ jobs:
           echo "$MODS"
           echo ""
           
-          # Extract just the module list (last line that isn't stderr logging)
-          MODULE_LIST=$(echo "$MODS" | grep -v "^Detected base ref:" | grep -v "^Changed files" | grep -v "^Final module list:" | tail -1)
+          # Extract just the final result (last line that looks like a module or <none>)
+          MODULE_LIST=$(echo "$MODS" | grep -E "^(vector-stores|spring-ai|models|<none>|$)" | tail -1)
+          if [ -z "$MODULE_LIST" ]; then
+            # If no clear module match, try the very last non-empty line
+            MODULE_LIST=$(echo "$MODS" | grep -v "^$" | tail -1)
+          fi
           echo "Extracted modules: '$MODULE_LIST'"
           echo "modules=$MODULE_LIST" >> "$GITHUB_OUTPUT"