fix: resolve git state issues causing full project builds

- Use fetch-depth: 2 instead of conflicting fetch-depth: 0 + --depth=1
- Switch to reliable git diff HEAD~1 HEAD for maintenance branches
- Eliminates issue where git show HEAD returned entire project history

Author: markpollack

.github/scripts/test_discovery.py

@@ -62,10 +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 git show HEAD regardless of base_ref
+            # For maintenance branches (cherry-picks), use single commit diff
             if branch and branch.endswith('.x'):
-                # Maintenance branch - cherry-picks are single commits, just get files in this commit
-                cmd = ["git", "show", "--name-only", "--format=", "HEAD"]
+                # Maintenance branch - use diff with previous commit
+                cmd = ["git", "diff", "--name-only", "HEAD~1", "HEAD"]
             elif base_ref:
                 # Explicit base reference provided - use two-dot diff for direct comparison
                 cmd = ["git", "diff", "--name-only", f"{base_ref}..HEAD"]
@@ -180,7 +180,7 @@ def _detect_default_base(self) -> str:
 
         # Show the actual strategy being used
         if branch and branch.endswith('.x'):
-            return f"git show HEAD (maintenance branch {branch})"
+            return f"git diff HEAD~1 HEAD (maintenance branch {branch})"
         elif pr_base:
             return f"origin/{pr_base} (PR base)"
         elif branch:

.github/workflows/maintenance-fast.yml

@@ -15,7 +15,7 @@ jobs:
       cancel-in-progress: true
     steps:
       - uses: actions/checkout@v4
-        with: { fetch-depth: 2 }  # Ensure we have at least HEAD~1 available
+        with: { fetch-depth: 2 }  # Need HEAD and HEAD~1 for single commit diff
 
       - uses: actions/setup-java@v4
         with: