fix: cache git branch detection to avoid repeated execSync calls

Previously, getCurrentGitBranch() was called inside loops for every
file processed during sync pull/push operations. For workspaces with
1900+ files, this spawned thousands of git subprocesses, causing a ~2x
performance regression.

This fix caches the git branch at the start of:
- elementsToMap() for pull operations
- push() for push operations

Expected improvement: ~3.2s -> ~1.6s for large workspaces.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cli/src/commands/sync/sync.ts

@@ -1283,6 +1283,8 @@ export async function elementsToMap(
 ): Promise<{ [key: string]: string }> {
   const map: { [key: string]: string } = {};
   const processedBasePaths = new Set<string>();
+  // Cache git branch at the start to avoid repeated execSync calls per file
+  const cachedBranch = branchOverride ?? getCurrentGitBranch() ?? undefined;
   for await (const entry of readDirRecursiveWithIgnore(ignore, els)) {
     // console.log("FOO", entry.path, entry.ignored, entry.isDirectory)
     if (entry.isDirectory || entry.ignored) {
@@ -1383,7 +1385,7 @@ export async function elementsToMap(
 
     // Handle branch-specific files - skip files for other branches
     if (specificItems && isBranchSpecificFile(path)) {
-      if (!isCurrentBranchFile(path, branchOverride)) {
+      if (!isCurrentBranchFile(path, cachedBranch)) {
         // Skip branch-specific files for other branches
         continue;
       }
@@ -1418,9 +1420,9 @@ export async function elementsToMap(
     }
 
     // Handle branch-specific path mapping after all filtering
-    if (isCurrentBranchFile(path, branchOverride)) {
+    if (cachedBranch && isCurrentBranchFile(path, cachedBranch)) {
       // This is a branch-specific file for current branch
-      const currentBranch = branchOverride || getCurrentGitBranch()!;
+      const currentBranch = cachedBranch;
       const basePath = fromBranchSpecificPath(path, currentBranch);
 
       // Only use branch-specific files if the item type IS configured as branch-specific
@@ -1952,6 +1954,7 @@ export async function pull(
   } catch {
     // ignore
   }
+
   const zipFile = await downloadZip(
     workspace,
     opts.plainSecrets,
@@ -1976,9 +1979,11 @@ export async function pull(
     resourceTypeToFormatExtension,
     true,
   );
+
   const local = !opts.stateful
     ? await FSFSElement(Deno.cwd(), codebases, true)
     : await FSFSElement(path.join(Deno.cwd(), ".wmill"), [], true);
+
   const changes = await compareDynFSElement(
     remote,
     local,
@@ -2675,6 +2680,8 @@ export async function push(
     // Create a pool of workers that processes items as they become available
     const pool = new Set();
     const queue = [...groupedChangesArray];
+    // Cache git branch at the start to avoid repeated execSync calls per change
+    const cachedBranchForPush = opts.branch || (isGitRepository() ? getCurrentGitBranch() : null);
 
     while (queue.length > 0 || pool.size > 0) {
       // Fill the pool until we reach parallelizationFactor
@@ -2759,7 +2766,7 @@ export async function push(
                   // For branch-specific resources, push to the base path on the workspace server
                   // This ensures branch-specific files are stored with their base names in the workspace
                   let serverPath = resourceFilePath;
-                  const currentBranch = opts.branch || (isGitRepository() ? getCurrentGitBranch() : null);
+                  const currentBranch = cachedBranchForPush;
 
                   if (currentBranch && isBranchSpecificFile(resourceFilePath)) {
                     serverPath = fromBranchSpecificPath(