feat: defer remote branch creation until first commit (#244)

* feat: defer remote branch creation until first commit

- For commit signing: branches are created remotely by github-file-ops-server on first commit
- For non-signing: branches are created locally with 'git checkout -b' and pushed when needed
- Consolidated duplicate branch creation logic in github-file-ops-server into a shared helper function
- Claude is unaware of these implementation details and simply sees it's on the correct branch
- No branch links are shown in initial comments since branches don't exist remotely yet

* fix: prevent broken branch links in final comment update

- Check if branch exists remotely before adding branch link
- Only add branch links for branches that actually exist on GitHub
- Add test coverage for non-existent remote branches
- Fixes issue where users would see broken branch links for local-only branches

* fix: don't show branch name in comment header when branch doesn't exist remotely

- Only pass branchName to updateCommentBody when branchLink exists
- Prevents showing branch names for branches that only exist locally
- Add test to verify branch name is not shown when branch doesn't exist

* tmp

src/github/operations/branch.ts

@@ -84,12 +84,8 @@ export async function setupBranch(
     sourceBranch = repoResponse.data.default_branch;
   }
 
-  // Creating a new branch for either an issue or closed/merged PR
+  // Generate branch name for either an issue or closed/merged PR
   const entityType = isPR ? "pr" : "issue";
-  console.log(
-    `Creating new branch for ${entityType} #${entityNumber} from source branch: ${sourceBranch}...`,
-  );
-
   const timestamp = new Date()
     .toISOString()
     .replace(/[:-]/g, "")
@@ -100,7 +96,7 @@ export async function setupBranch(
   const newBranch = `${branchPrefix}${entityType}-${entityNumber}-${timestamp}`;
 
   try {
-    // Get the SHA of the source branch
+    // Get the SHA of the source branch to verify it exists
     const sourceBranchRef = await octokits.rest.git.getRef({
       owner,
       repo,
@@ -108,23 +104,34 @@ export async function setupBranch(
     });
 
     const currentSHA = sourceBranchRef.data.object.sha;
+    console.log(`Source branch SHA: ${currentSHA}`);
 
-    console.log(`Current SHA: ${currentSHA}`);
+    // For commit signing, defer branch creation to the file ops server
+    if (context.inputs.useCommitSigning) {
+      console.log(
+        `Branch name generated: ${newBranch} (will be created by file ops server on first commit)`,
+      );
 
-    // Create branch using GitHub API
-    await octokits.rest.git.createRef({
-      owner,
-      repo,
-      ref: `refs/heads/${newBranch}`,
-      sha: currentSHA,
-    });
+      // Set outputs for GitHub Actions
+      core.setOutput("CLAUDE_BRANCH", newBranch);
+      core.setOutput("BASE_BRANCH", sourceBranch);
+      return {
+        baseBranch: sourceBranch,
+        claudeBranch: newBranch,
+        currentBranch: sourceBranch, // Stay on source branch for now
+      };
+    }
 
-    // Checkout the new branch (shallow fetch for performance)
-    await $`git fetch origin --depth=1 ${newBranch}`;
-    await $`git checkout ${newBranch}`;
+    // For non-signing case, create and checkout the branch locally only
+    console.log(
+      `Creating local branch ${newBranch} for ${entityType} #${entityNumber} from source branch: ${sourceBranch}...`,
+    );
+
+    // Create and checkout the new branch locally
+    await $`git checkout -b ${newBranch}`;
 
     console.log(
-      `Successfully created and checked out new branch: ${newBranch}`,
+      `Successfully created and checked out local branch: ${newBranch}`,
     );
 
     // Set outputs for GitHub Actions
@@ -136,7 +143,7 @@ export async function setupBranch(
       currentBranch: newBranch,
     };
   } catch (error) {
-    console.error("Error creating branch:", error);
+    console.error("Error in branch setup:", error);
     process.exit(1);
   }
 }