dont push empty bundles

dist/index.js

@@ -41983,18 +41983,27 @@ async function uploadBranchDelta(settings) {
     }
     const repoPath = settings.repositoryPath;
     const sha = settings.commit;
+    await exec_exec('git', ['-C', repoPath, 'update-ref', UPLOAD_TIP_REF, sha]);
+    try {
+        if (!(await hasBaseRefs(repoPath))) {
+            info('No base refs to diff against; branch delta skipped');
+            return;
+        }
+        // If the tip is already in the base there is no delta to roll, and `git bundle
+        // create` errors on an empty range ("Refusing to create empty bundle"). Detect it
+        // first — and before taking the server lock, so an empty delta never blocks the
+        // other jobs racing the same branch.
+        if (await branchDeltaIsEmpty(repoPath)) {
+            info('Tip already contained in the base; no branch delta to upload');
+            return;
+        }
         const grant = await requestBranchUpload(plan.repoKey, plan.refKey, sha);
         if (grant.kind !== 'grant') {
             info(`Branch delta upload skipped (${grant.kind})`);
             return;
         }
-    if (!(await hasBaseRefs(repoPath))) {
-        info('No base refs to diff against; branch delta skipped');
-        return;
-    }
         const tmp = tempBundlePath('branch');
         try {
-        await exec_exec('git', ['-C', repoPath, 'update-ref', UPLOAD_TIP_REF, sha]);
             // Exclude the base with a single --glob, not one `^ref` arg per ref: a large repo
             // has hundreds of base refs, and that many args overflows the Windows command-line
             // limit (ENAMETOOLONG). The glob matches the multi-level seeded refs and yields the
@@ -42014,11 +42023,29 @@ async function uploadBranchDelta(settings) {
         }
         finally {
             await external_fs_namespaceObject.promises.rm(tmp, { force: true });
+        }
+    }
+    finally {
         await exec_exec('git', ['-C', repoPath, 'update-ref', '-d', UPLOAD_TIP_REF], {
             ignoreReturnCode: true
         });
     }
 }
+// The tip's delta against the base is empty when the tip is already reachable from the
+// base — nothing new to bundle.
+async function branchDeltaIsEmpty(repoPath) {
+    let out = '';
+    await exec_exec('git', [
+        '-C',
+        repoPath,
+        'rev-list',
+        '--count',
+        UPLOAD_TIP_REF,
+        '--not',
+        `--glob=${BASE_REFNS}/*`
+    ], { silent: true, listeners: { stdout: (d) => (out += d.toString()) } });
+    return out.trim() === '0';
+}
 // Whether any base ref was seeded — the guard that keeps the delta base-relative. The
 // base is excluded by glob (see uploadBranchDelta), so we only need existence here.
 async function hasBaseRefs(repoPath) {

src/warpbuild/mirror-cache.ts

@@ -248,20 +248,29 @@ async function uploadBranchDelta(settings: IGitSourceSettings): Promise<void> {
   const repoPath = settings.repositoryPath
   const sha = settings.commit
 
+  await exec.exec('git', ['-C', repoPath, 'update-ref', UPLOAD_TIP_REF, sha])
+  try {
+    if (!(await hasBaseRefs(repoPath))) {
+      core.info('No base refs to diff against; branch delta skipped')
+      return
+    }
+    // If the tip is already in the base there is no delta to roll, and `git bundle
+    // create` errors on an empty range ("Refusing to create empty bundle"). Detect it
+    // first — and before taking the server lock, so an empty delta never blocks the
+    // other jobs racing the same branch.
+    if (await branchDeltaIsEmpty(repoPath)) {
+      core.info('Tip already contained in the base; no branch delta to upload')
+      return
+    }
+
     const grant = await api.requestBranchUpload(plan.repoKey, plan.refKey, sha)
     if (grant.kind !== 'grant') {
       core.info(`Branch delta upload skipped (${grant.kind})`)
       return
     }
 
-  if (!(await hasBaseRefs(repoPath))) {
-    core.info('No base refs to diff against; branch delta skipped')
-    return
-  }
-
     const tmp = tempBundlePath('branch')
     try {
-    await exec.exec('git', ['-C', repoPath, 'update-ref', UPLOAD_TIP_REF, sha])
       // Exclude the base with a single --glob, not one `^ref` arg per ref: a large repo
       // has hundreds of base refs, and that many args overflows the Windows command-line
       // limit (ENAMETOOLONG). The glob matches the multi-level seeded refs and yields the
@@ -280,6 +289,8 @@ async function uploadBranchDelta(settings: IGitSourceSettings): Promise<void> {
       core.info(`Uploaded branch delta for '${plan.refKey}'`)
     } finally {
       await fs.promises.rm(tmp, {force: true})
+    }
+  } finally {
     await exec.exec(
       'git',
       ['-C', repoPath, 'update-ref', '-d', UPLOAD_TIP_REF],
@@ -290,6 +301,26 @@ async function uploadBranchDelta(settings: IGitSourceSettings): Promise<void> {
   }
 }
 
+// The tip's delta against the base is empty when the tip is already reachable from the
+// base — nothing new to bundle.
+async function branchDeltaIsEmpty(repoPath: string): Promise<boolean> {
+  let out = ''
+  await exec.exec(
+    'git',
+    [
+      '-C',
+      repoPath,
+      'rev-list',
+      '--count',
+      UPLOAD_TIP_REF,
+      '--not',
+      `--glob=${BASE_REFNS}/*`
+    ],
+    {silent: true, listeners: {stdout: (d: Buffer) => (out += d.toString())}}
+  )
+  return out.trim() === '0'
+}
+
 // Whether any base ref was seeded — the guard that keeps the delta base-relative. The
 // base is excluded by glob (see uploadBranchDelta), so we only need existence here.
 async function hasBaseRefs(repoPath: string): Promise<boolean> {