feat(git): add GetCurrentBranchAsync

src/ClaudeDo.Data/Git/GitService.cs

@@ -151,6 +151,15 @@ public sealed class GitService
             throw new InvalidOperationException($"git branch {flag} failed (exit {exitCode}): {stderr}");
     }
 
+    public async Task<string> GetCurrentBranchAsync(string repoDir, CancellationToken ct = default)
+    {
+        var (exitCode, stdout, stderr) = await RunGitAsync(repoDir,
+            ["symbolic-ref", "--short", "HEAD"], ct);
+        if (exitCode != 0)
+            throw new InvalidOperationException($"git symbolic-ref --short HEAD failed (exit {exitCode}): {stderr}");
+        return stdout.Trim();
+    }
+
     public async Task MergeFfOnlyAsync(string repoDir, string branchName, CancellationToken ct = default)
     {
         var (exitCode, _, stderr) = await RunGitAsync(repoDir, ["merge", "--ff-only", branchName], ct);

tests/ClaudeDo.Worker.Tests/Runner/GitServiceMergeTests.cs

@@ -0,0 +1,37 @@
+using ClaudeDo.Data.Git;
+using ClaudeDo.Worker.Tests.Infrastructure;
+
+namespace ClaudeDo.Worker.Tests.Runner;
+
+public class GitServiceMergeTests : IDisposable
+{
+    private readonly List<GitRepoFixture> _repos = new();
+
+    private GitRepoFixture NewRepo()
+    {
+        var r = new GitRepoFixture();
+        _repos.Add(r);
+        return r;
+    }
+
+    public void Dispose()
+    {
+        foreach (var r in _repos) try { r.Dispose(); } catch { }
+    }
+
+    [Fact]
+    public async Task GetCurrentBranchAsync_FreshRepo_ReturnsDefaultBranch()
+    {
+        if (!GitRepoFixture.IsGitAvailable()) return;
+
+        var repo = NewRepo();
+        var git = new GitService();
+
+        var branch = await git.GetCurrentBranchAsync(repo.RepoDir);
+
+        Assert.False(string.IsNullOrWhiteSpace(branch));
+        // Default branch is either "main" or "master" depending on git config.
+        Assert.True(branch == "main" || branch == "master",
+            $"Expected main or master, got '{branch}'");
+    }
+}