feat(scripts): add --allow-existing-branch flag to create-new-feature

scripts/bash/create-new-feature.sh

@@ -3,6 +3,7 @@
 set -e
 
 JSON_MODE=false
+ALLOW_EXISTING=false
 SHORT_NAME=""
 BRANCH_NUMBER=""
 USE_TIMESTAMP=false
@@ -14,6 +15,9 @@ while [ $i -le $# ]; do
         --json)
             JSON_MODE=true
             ;;
+        --allow-existing-branch)
+            ALLOW_EXISTING=true
+            ;;
         --short-name)
             if [ $((i + 1)) -gt $# ]; then
                 echo 'Error: --short-name requires a value' >&2
@@ -45,10 +49,11 @@ while [ $i -le $# ]; do
             USE_TIMESTAMP=true
             ;;
         --help|-h)
-            echo "Usage: $0 [--json] [--short-name <name>] [--number N] [--timestamp] <feature_description>"
+            echo "Usage: $0 [--json] [--allow-existing-branch] [--short-name <name>] [--number N] [--timestamp] <feature_description>"
             echo ""
             echo "Options:"
             echo "  --json              Output in JSON format"
+            echo "  --allow-existing-branch  Switch to branch if it already exists instead of failing"
             echo "  --short-name <name> Provide a custom short name (2-4 words) for the branch"
             echo "  --number N          Specify branch number manually (overrides auto-detection)"
             echo "  --timestamp         Use timestamp prefix (YYYYMMDD-HHMMSS) instead of sequential numbering"
@@ -69,7 +74,7 @@ done
 
 FEATURE_DESCRIPTION="${ARGS[*]}"
 if [ -z "$FEATURE_DESCRIPTION" ]; then
-    echo "Usage: $0 [--json] [--short-name <name>] [--number N] [--timestamp] <feature_description>" >&2
+    echo "Usage: $0 [--json] [--allow-existing-branch] [--short-name <name>] [--number N] [--timestamp] <feature_description>" >&2
     exit 1
 fi
 
@@ -287,12 +292,19 @@ if [ "$HAS_GIT" = true ]; then
     if ! git checkout -b "$BRANCH_NAME" 2>/dev/null; then
         # Check if branch already exists
         if git branch --list "$BRANCH_NAME" | grep -q .; then
-            if [ "$USE_TIMESTAMP" = true ]; then
+            if [ "$ALLOW_EXISTING" = true ]; then
+                # Switch to the existing branch instead of failing
+                if ! git checkout "$BRANCH_NAME" 2>/dev/null; then
+                    >&2 echo "Error: Failed to switch to existing branch '$BRANCH_NAME'. Please resolve any local changes or conflicts and try again."
+                    exit 1
+                fi
+            elif [ "$USE_TIMESTAMP" = true ]; then
                 >&2 echo "Error: Branch '$BRANCH_NAME' already exists. Rerun to get a new timestamp or use a different --short-name."
+                exit 1
             else
                 >&2 echo "Error: Branch '$BRANCH_NAME' already exists. Please use a different feature name or specify a different number with --number."
+                exit 1
             fi
-            exit 1
         else
             >&2 echo "Error: Failed to create git branch '$BRANCH_NAME'. Please check your git configuration and try again."
             exit 1
@@ -305,13 +317,15 @@ fi
 FEATURE_DIR="$SPECS_DIR/$BRANCH_NAME"
 mkdir -p "$FEATURE_DIR"
 
-TEMPLATE=$(resolve_template "spec-template" "$REPO_ROOT") || true
 SPEC_FILE="$FEATURE_DIR/spec.md"
-if [ -n "$TEMPLATE" ] && [ -f "$TEMPLATE" ]; then
-    cp "$TEMPLATE" "$SPEC_FILE"
-else
-    echo "Warning: Spec template not found; created empty spec file" >&2
-    touch "$SPEC_FILE"
+if [ ! -f "$SPEC_FILE" ]; then
+    TEMPLATE=$(resolve_template "spec-template" "$REPO_ROOT") || true
+    if [ -n "$TEMPLATE" ] && [ -f "$TEMPLATE" ]; then
+        cp "$TEMPLATE" "$SPEC_FILE"
+    else
+        echo "Warning: Spec template not found; created empty spec file" >&2
+        touch "$SPEC_FILE"
+    fi
 fi
 
 # Inform the user how to persist the feature variable in their own shell

scripts/powershell/create-new-feature.ps1

@@ -3,6 +3,7 @@
 [CmdletBinding()]
 param(
     [switch]$Json,
+    [switch]$AllowExistingBranch,
     [string]$ShortName,
     [Parameter()]
     [long]$Number = 0,
@@ -15,10 +16,11 @@ $ErrorActionPreference = 'Stop'
 
 # Show help if requested
 if ($Help) {
-    Write-Host "Usage: ./create-new-feature.ps1 [-Json] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
+    Write-Host "Usage: ./create-new-feature.ps1 [-Json] [-AllowExistingBranch] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
     Write-Host ""
     Write-Host "Options:"
     Write-Host "  -Json               Output in JSON format"
+    Write-Host "  -AllowExistingBranch  Switch to branch if it already exists instead of failing"
     Write-Host "  -ShortName <name>   Provide a custom short name (2-4 words) for the branch"
     Write-Host "  -Number N           Specify branch number manually (overrides auto-detection)"
     Write-Host "  -Timestamp          Use timestamp prefix (YYYYMMDD-HHMMSS) instead of sequential numbering"
@@ -33,7 +35,7 @@ if ($Help) {
 
 # Check if feature description provided
 if (-not $FeatureDescription -or $FeatureDescription.Count -eq 0) {
-    Write-Error "Usage: ./create-new-feature.ps1 [-Json] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
+    Write-Error "Usage: ./create-new-feature.ps1 [-Json] [-AllowExistingBranch] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
     exit 1
 }
 
@@ -251,12 +253,20 @@ if ($hasGit) {
         # Check if branch already exists
         $existingBranch = git branch --list $branchName 2>$null
         if ($existingBranch) {
-            if ($Timestamp) {
+            if ($AllowExistingBranch) {
+                # Switch to the existing branch instead of failing
+                git checkout -q $branchName 2>$null | Out-Null
+                if ($LASTEXITCODE -ne 0) {
+                    Write-Error "Error: Branch '$branchName' exists but could not be checked out. Resolve any uncommitted changes or conflicts and try again."
+                    exit 1
+                }
+            } elseif ($Timestamp) {
                 Write-Error "Error: Branch '$branchName' already exists. Rerun to get a new timestamp or use a different -ShortName."
+                exit 1
             } else {
                 Write-Error "Error: Branch '$branchName' already exists. Please use a different feature name or specify a different number with -Number."
+                exit 1
             }
-            exit 1
         } else {
             Write-Error "Error: Failed to create git branch '$branchName'. Please check your git configuration and try again."
             exit 1
@@ -269,12 +279,14 @@ if ($hasGit) {
 $featureDir = Join-Path $specsDir $branchName
 New-Item -ItemType Directory -Path $featureDir -Force | Out-Null
 
-$template = Resolve-Template -TemplateName 'spec-template' -RepoRoot $repoRoot
 $specFile = Join-Path $featureDir 'spec.md'
-if ($template -and (Test-Path $template)) { 
-    Copy-Item $template $specFile -Force 
-} else { 
-    New-Item -ItemType File -Path $specFile | Out-Null 
+if (-not (Test-Path -PathType Leaf $specFile)) {
+    $template = Resolve-Template -TemplateName 'spec-template' -RepoRoot $repoRoot
+    if ($template -and (Test-Path $template)) {
+        Copy-Item $template $specFile -Force
+    } else {
+        New-Item -ItemType File -Path $specFile | Out-Null
+    }
 }
 
 # Set the SPECIFY_FEATURE environment variable for the current session

tests/test_timestamp_branches.py

@@ -269,3 +269,146 @@ def test_e2e_sequential(self, git_repo: Path):
         assert (git_repo / "specs" / branch).is_dir()
         val = source_and_call(f'check_feature_branch "{branch}" "true"')
         assert val.returncode == 0
+
+
+# ── Allow Existing Branch Tests ──────────────────────────────────────────────
+
+
+class TestAllowExistingBranch:
+    def test_allow_existing_switches_to_branch(self, git_repo: Path):
+        """T006: Pre-create branch, verify script switches to it."""
+        subprocess.run(
+            ["git", "checkout", "-b", "004-pre-exist"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        subprocess.run(
+            ["git", "checkout", "-"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--short-name", "pre-exist",
+            "--number", "4", "Pre-existing feature",
+        )
+        assert result.returncode == 0, result.stderr
+        current = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=git_repo, capture_output=True, text=True,
+        ).stdout.strip()
+        assert current == "004-pre-exist", f"expected 004-pre-exist, got {current}"
+
+    def test_allow_existing_already_on_branch(self, git_repo: Path):
+        """T007: Verify success when already on the target branch."""
+        subprocess.run(
+            ["git", "checkout", "-b", "005-already-on"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--short-name", "already-on",
+            "--number", "5", "Already on branch",
+        )
+        assert result.returncode == 0, result.stderr
+
+    def test_allow_existing_creates_spec_dir(self, git_repo: Path):
+        """T008: Verify spec directory created on existing branch."""
+        subprocess.run(
+            ["git", "checkout", "-b", "006-spec-dir"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        subprocess.run(
+            ["git", "checkout", "-"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--short-name", "spec-dir",
+            "--number", "6", "Spec dir feature",
+        )
+        assert result.returncode == 0, result.stderr
+        assert (git_repo / "specs" / "006-spec-dir").is_dir()
+        assert (git_repo / "specs" / "006-spec-dir" / "spec.md").exists()
+
+    def test_without_flag_still_errors(self, git_repo: Path):
+        """T009: Verify backwards compatibility (error without flag)."""
+        subprocess.run(
+            ["git", "checkout", "-b", "007-no-flag"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        subprocess.run(
+            ["git", "checkout", "-"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--short-name", "no-flag", "--number", "7", "No flag feature",
+        )
+        assert result.returncode != 0, "should fail without --allow-existing-branch"
+        assert "already exists" in result.stderr
+
+    def test_allow_existing_no_overwrite_spec(self, git_repo: Path):
+        """T010: Pre-create spec.md with content, verify it is preserved."""
+        subprocess.run(
+            ["git", "checkout", "-b", "008-no-overwrite"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        spec_dir = git_repo / "specs" / "008-no-overwrite"
+        spec_dir.mkdir(parents=True)
+        spec_file = spec_dir / "spec.md"
+        spec_file.write_text("# My custom spec content\n")
+        subprocess.run(
+            ["git", "checkout", "-"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--short-name", "no-overwrite",
+            "--number", "8", "No overwrite feature",
+        )
+        assert result.returncode == 0, result.stderr
+        assert spec_file.read_text() == "# My custom spec content\n"
+
+    def test_allow_existing_creates_branch_if_not_exists(self, git_repo: Path):
+        """T011: Verify normal creation when branch doesn't exist."""
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--short-name", "new-branch",
+            "New branch feature",
+        )
+        assert result.returncode == 0, result.stderr
+        current = subprocess.run(
+            ["git", "rev-parse", "--abbrev-ref", "HEAD"],
+            cwd=git_repo, capture_output=True, text=True,
+        ).stdout.strip()
+        assert "new-branch" in current
+
+    def test_allow_existing_with_json(self, git_repo: Path):
+        """T012: Verify JSON output is correct."""
+        import json
+
+        subprocess.run(
+            ["git", "checkout", "-b", "009-json-test"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        subprocess.run(
+            ["git", "checkout", "-"],
+            cwd=git_repo, check=True, capture_output=True,
+        )
+        result = run_script(
+            git_repo, "--allow-existing-branch", "--json", "--short-name", "json-test",
+            "--number", "9", "JSON test",
+        )
+        assert result.returncode == 0, result.stderr
+        data = json.loads(result.stdout)
+        assert data["BRANCH_NAME"] == "009-json-test"
+
+    def test_allow_existing_no_git(self, no_git_dir: Path):
+        """T013: Verify flag is silently ignored in non-git repos."""
+        result = run_script(
+            no_git_dir, "--allow-existing-branch", "--short-name", "no-git",
+            "No git feature",
+        )
+        assert result.returncode == 0, result.stderr
+
+
+class TestAllowExistingBranchPowerShell:
+    def test_powershell_supports_allow_existing_branch_flag(self):
+        """Static guard: PS script exposes and uses -AllowExistingBranch."""
+        contents = CREATE_FEATURE_PS.read_text(encoding="utf-8")
+        assert "-AllowExistingBranch" in contents
+        # Ensure the flag is referenced in script logic, not just declared
+        assert "AllowExistingBranch" in contents.replace("-AllowExistingBranch", "")