fix: improve error handling and logging for diff range path resolution

lib/upload-lib.js

@@ -107530,10 +107530,19 @@ function computeChangedFiles(baseFileOids, overlayFileOids) {
 }
 async function getDiffRangeFilePaths(sourceRoot, logger) {
   const jsonFilePath = getDiffRangesJsonFilePath();
+  if (!fs3.existsSync(jsonFilePath)) {
+    logger.debug(
+      `No diff ranges JSON file found at ${jsonFilePath}; skipping.`
+    );
+    return [];
+  }
   let contents;
   try {
     contents = await fs3.promises.readFile(jsonFilePath, "utf8");
-  } catch {
+  } catch (e) {
+    logger.warning(
+      `Failed to read diff ranges JSON file at ${jsonFilePath}: ${e}`
+    );
     return [];
   }
   let diffRanges;
@@ -107550,6 +107559,11 @@ async function getDiffRangeFilePaths(sourceRoot, logger) {
   );
   const repoRoot = await getGitRoot(sourceRoot);
   if (repoRoot === void 0) {
+    if (getOptionalInput("source-root")) {
+      throw new Error(
+        "Cannot determine git root to convert diff range paths relative to source-root. Failing to avoid omitting files from the analysis."
+      );
+    }
     logger.warning(
       "Cannot determine git root; returning diff range paths as-is."
     );