feat: create extensions/git with manifest, commands, scripts, and auto-install in init

Co-authored-by: mnriem <15701806+mnriem@users.noreply.github.com>
Agent-Logs-Url: https://github.com/github/spec-kit/sessions/809a1dbf-1301-4312-b4d2-e18f9b3e8b2f

extensions/git/README.md

@@ -0,0 +1,85 @@
+# Git Branching Workflow Extension
+
+Feature branch creation, numbering (sequential/timestamp), validation, and Git remote detection for Spec Kit.
+
+## Overview
+
+This extension provides Git branching operations as an optional, self-contained module. It manages:
+
+- **Feature branch creation** with sequential (`001-feature-name`) or timestamp (`20260319-143022-feature-name`) numbering
+- **Branch validation** to ensure branches follow naming conventions
+- **Git remote detection** for GitHub integration (e.g., issue creation)
+
+## Commands
+
+| Command | Description |
+|---------|-------------|
+| `speckit.git.feature` | Create a feature branch with sequential or timestamp numbering |
+| `speckit.git.validate` | Validate current branch follows feature branch naming conventions |
+| `speckit.git.remote` | Detect Git remote URL for GitHub integration |
+
+## Hooks
+
+| Event | Command | Optional | Description |
+|-------|---------|----------|-------------|
+| `before_specify` | `speckit.git.feature` | No | Create feature branch before specification |
+| `after_implement` | `speckit.git.validate` | Yes | Validate branch naming after implementation |
+
+## Configuration
+
+Configuration is stored in `.specify/extensions/git/git-config.yml`:
+
+```yaml
+# Branch numbering strategy: "sequential" or "timestamp"
+branch_numbering: sequential
+
+# Branch name template
+branch_template: "{number}-{short_name}"
+
+# Whether to fetch remotes before computing next branch number
+auto_fetch: true
+```
+
+### Environment Variable Override
+
+Set `SPECKIT_GIT_BRANCH_NUMBERING` to override the `branch_numbering` config value:
+
+```bash
+export SPECKIT_GIT_BRANCH_NUMBERING=timestamp
+```
+
+## Installation
+
+```bash
+# Install from the bundled extension
+specify extension add git --from extensions/git/
+
+# Or it auto-installs during specify init (migration period)
+```
+
+## Disabling
+
+```bash
+# Disable the git extension (spec creation continues without branching)
+specify extension disable git
+
+# Re-enable it
+specify extension enable git
+```
+
+## Graceful Degradation
+
+When Git is not installed or the directory is not a Git repository:
+- Spec directories are still created under `specs/`
+- Branch creation is skipped with a warning
+- Branch validation is skipped with a warning
+- Remote detection returns empty results
+
+## Scripts
+
+The extension bundles cross-platform scripts:
+
+- `scripts/bash/create-new-feature.sh` — Bash implementation
+- `scripts/bash/git-common.sh` — Shared Git utilities (Bash)
+- `scripts/powershell/create-new-feature.ps1` — PowerShell implementation
+- `scripts/powershell/git-common.ps1` — Shared Git utilities (PowerShell)

extensions/git/commands/speckit.git.feature.md

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+---
+description: "Create a feature branch with sequential or timestamp numbering"
+---
+
+# Create Feature Branch
+
+Create a new feature branch for the given specification.
+
+## User Input
+
+```text
+$ARGUMENTS
+```
+
+You **MUST** consider the user input before proceeding (if not empty).
+
+## Prerequisites
+
+- Verify Git is available by running `git rev-parse --is-inside-work-tree 2>/dev/null`
+- If Git is not available, warn the user and skip branch creation (spec directory will still be created)
+
+## Branch Numbering Mode
+
+Determine the branch numbering strategy by checking configuration in this order:
+
+1. Check `.specify/extensions/git/git-config.yml` for `branch_numbering` value
+2. Check `.specify/init-options.json` for `branch_numbering` value (backward compatibility)
+3. Default to `sequential` if neither exists
+
+## Execution
+
+Generate a concise short name (2-4 words) for the branch:
+- Analyze the feature description and extract the most meaningful keywords
+- Use action-noun format when possible (e.g., "add-user-auth", "fix-payment-bug")
+- Preserve technical terms and acronyms (OAuth2, API, JWT, etc.)
+
+Run the appropriate script based on your platform:
+
+- **Bash**: `.specify/extensions/git/scripts/bash/create-new-feature.sh --json --short-name "<short-name>" "<feature description>"`
+- **Bash (timestamp)**: `.specify/extensions/git/scripts/bash/create-new-feature.sh --json --timestamp --short-name "<short-name>" "<feature description>"`
+- **PowerShell**: `.specify/extensions/git/scripts/powershell/create-new-feature.ps1 -Json -ShortName "<short-name>" "<feature description>"`
+- **PowerShell (timestamp)**: `.specify/extensions/git/scripts/powershell/create-new-feature.ps1 -Json -Timestamp -ShortName "<short-name>" "<feature description>"`
+
+**IMPORTANT**:
+- Do NOT pass `--number` — the script determines the correct next number automatically
+- Always include the JSON flag (`--json` for Bash, `-Json` for PowerShell) so the output can be parsed reliably
+- You must only ever run this script once per feature
+- The JSON output will contain BRANCH_NAME and SPEC_FILE paths
+
+If the extension scripts are not found at the `.specify/extensions/git/` path, fall back to:
+- **Bash**: `scripts/bash/create-new-feature.sh`
+- **PowerShell**: `scripts/powershell/create-new-feature.ps1`
+
+## Graceful Degradation
+
+If Git is not installed or the current directory is not a Git repository:
+- The script will still create the spec directory under `specs/`
+- A warning will be printed: `[specify] Warning: Git repository not detected; skipped branch creation`
+- The workflow continues normally without branch creation
+
+## Output
+
+The script outputs JSON with:
+- `BRANCH_NAME`: The created branch name (e.g., `003-user-auth` or `20260319-143022-user-auth`)
+- `SPEC_FILE`: Path to the created spec file
+- `FEATURE_NUM`: The numeric or timestamp prefix used

extensions/git/commands/speckit.git.remote.md

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+---
+description: "Detect Git remote URL for GitHub integration"
+---
+
+# Detect Git Remote URL
+
+Detect the Git remote URL for integration with GitHub services (e.g., issue creation).
+
+## Prerequisites
+
+- Check if Git is available by running `git rev-parse --is-inside-work-tree 2>/dev/null`
+- If Git is not available, output a warning and return empty:
+  ```
+  [specify] Warning: Git repository not detected; cannot determine remote URL
+  ```
+
+## Execution
+
+Run the following command to get the remote URL:
+
+```bash
+git config --get remote.origin.url
+```
+
+## Output
+
+Parse the remote URL and determine:
+
+1. **Repository owner**: Extract from the URL (e.g., `github` from `https://github.com/github/spec-kit.git`)
+2. **Repository name**: Extract from the URL (e.g., `spec-kit` from `https://github.com/github/spec-kit.git`)
+3. **Is GitHub**: Whether the remote points to a GitHub repository
+
+Supported URL formats:
+- HTTPS: `https://github.com/<owner>/<repo>.git`
+- SSH: `git@github.com:<owner>/<repo>.git`
+
+> [!CAUTION]
+> ONLY report a GitHub repository if the remote URL actually points to github.com.
+> Do NOT assume the remote is GitHub if the URL format doesn't match.
+
+## Graceful Degradation
+
+If Git is not installed, the directory is not a Git repository, or no remote is configured:
+- Return an empty result
+- Do NOT error — other workflows should continue without Git remote information

extensions/git/commands/speckit.git.validate.md

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+---
+description: "Validate current branch follows feature branch naming conventions"
+---
+
+# Validate Feature Branch
+
+Validate that the current Git branch follows the expected feature branch naming conventions.
+
+## Prerequisites
+
+- Check if Git is available by running `git rev-parse --is-inside-work-tree 2>/dev/null`
+- If Git is not available, output a warning and skip validation:
+  ```
+  [specify] Warning: Git repository not detected; skipped branch validation
+  ```
+
+## Validation Rules
+
+Get the current branch name:
+
+```bash
+git rev-parse --abbrev-ref HEAD
+```
+
+The branch name must match one of these patterns:
+
+1. **Sequential**: `^[0-9]{3}-` (e.g., `001-feature-name`, `042-fix-bug`)
+2. **Timestamp**: `^[0-9]{8}-[0-9]{6}-` (e.g., `20260319-143022-feature-name`)
+
+## Execution
+
+If on a feature branch (matches either pattern):
+- Output: `✓ On feature branch: <branch-name>`
+- Check if the corresponding spec directory exists under `specs/`:
+  - For sequential branches, look for `specs/<prefix>-*` where prefix matches the `###` portion
+  - For timestamp branches, look for `specs/<prefix>-*` where prefix matches the `YYYYMMDD-HHMMSS` portion
+- If spec directory exists: `✓ Spec directory found: <path>`
+- If spec directory missing: `⚠ No spec directory found for prefix <prefix>`
+
+If NOT on a feature branch:
+- Output: `✗ Not on a feature branch. Current branch: <branch-name>`
+- Output: `Feature branches should be named like: 001-feature-name or 20260319-143022-feature-name`
+
+## Graceful Degradation
+
+If Git is not installed or the directory is not a Git repository:
+- Check the `SPECIFY_FEATURE` environment variable as a fallback
+- If set, validate that value against the naming patterns
+- If not set, skip validation with a warning

extensions/git/config-template.yml

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+# Git Branching Workflow Extension Configuration
+# Copy this file to .specify/extensions/git/git-config.yml to customize
+
+# Branch numbering strategy: "sequential" (001, 002, ...) or "timestamp" (YYYYMMDD-HHMMSS)
+branch_numbering: sequential
+
+# Branch name template (used with sequential numbering)
+# Available placeholders: {number}, {short_name}
+branch_template: "{number}-{short_name}"
+
+# Whether to run `git fetch --all --prune` before computing the next branch number
+auto_fetch: true

extensions/git/extension.yml

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+schema_version: "1.0"
+
+extension:
+  id: git
+  name: "Git Branching Workflow"
+  version: "1.0.0"
+  description: "Feature branch creation, numbering (sequential/timestamp), validation, and Git remote detection"
+  author: spec-kit-core
+  repository: https://github.com/github/spec-kit
+  license: MIT
+
+requires:
+  speckit_version: ">=0.2.0"
+  tools:
+    - name: git
+      required: false
+
+provides:
+  commands:
+    - name: speckit.git.feature
+      file: commands/speckit.git.feature.md
+      description: "Create a feature branch with sequential or timestamp numbering"
+    - name: speckit.git.validate
+      file: commands/speckit.git.validate.md
+      description: "Validate current branch follows feature branch naming conventions"
+    - name: speckit.git.remote
+      file: commands/speckit.git.remote.md
+      description: "Detect Git remote URL for GitHub integration"
+
+hooks:
+  before_specify:
+    command: speckit.git.feature
+    optional: false
+    description: "Create feature branch before specification"
+  after_implement:
+    command: speckit.git.validate
+    optional: true
+    prompt: "Verify feature branch naming?"
+    description: "Validate branch naming after implementation"
+
+tags:
+  - "git"
+  - "branching"
+  - "workflow"
+
+defaults:
+  branch_numbering: sequential
+  branch_template: "{number}-{short_name}"
+  auto_fetch: true

extensions/git/scripts/bash/create-new-feature.sh

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+#!/usr/bin/env bash
+
+set -e
+
+JSON_MODE=false
+SHORT_NAME=""
+BRANCH_NUMBER=""
+USE_TIMESTAMP=false
+ARGS=()
+i=1
+while [ $i -le $# ]; do
+    arg="${!i}"
+    case "$arg" in
+        --json)
+            JSON_MODE=true
+            ;;
+        --short-name)
+            if [ $((i + 1)) -gt $# ]; then
+                echo 'Error: --short-name requires a value' >&2
+                exit 1
+            fi
+            i=$((i + 1))
+            next_arg="${!i}"
+            # Check if the next argument is another option (starts with --)
+            if [[ "$next_arg" == --* ]]; then
+                echo 'Error: --short-name requires a value' >&2
+                exit 1
+            fi
+            SHORT_NAME="$next_arg"
+            ;;
+        --number)
+            if [ $((i + 1)) -gt $# ]; then
+                echo 'Error: --number requires a value' >&2
+                exit 1
+            fi
+            i=$((i + 1))
+            next_arg="${!i}"
+            if [[ "$next_arg" == --* ]]; then
+                echo 'Error: --number requires a value' >&2
+                exit 1
+            fi
+            BRANCH_NUMBER="$next_arg"
+            ;;
+        --timestamp)
+            USE_TIMESTAMP=true
+            ;;
+        --help|-h)
+            echo "Usage: $0 [--json] [--short-name <name>] [--number N] [--timestamp] <feature_description>"
+            echo ""
+            echo "Options:"
+            echo "  --json              Output in JSON format"
+            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"
+            echo "  --help, -h          Show this help message"
+            echo ""
+            echo "Examples:"
+            echo "  $0 'Add user authentication system' --short-name 'user-auth'"
+            echo "  $0 'Implement OAuth2 integration for API' --number 5"
+            echo "  $0 --timestamp --short-name 'user-auth' 'Add user authentication'"
+            exit 0
+            ;;
+        *)
+            ARGS+=("$arg")
+            ;;
+    esac
+    i=$((i + 1))
+done
+
+FEATURE_DESCRIPTION="${ARGS[*]}"
+if [ -z "$FEATURE_DESCRIPTION" ]; then
+    echo "Usage: $0 [--json] [--short-name <name>] [--number N] [--timestamp] <feature_description>" >&2
+    exit 1
+fi
+
+# Trim whitespace and validate description is not empty (e.g., user passed only whitespace)
+FEATURE_DESCRIPTION=$(echo "$FEATURE_DESCRIPTION" | xargs)
+if [ -z "$FEATURE_DESCRIPTION" ]; then
+    echo "Error: Feature description cannot be empty or contain only whitespace" >&2
+    exit 1
+fi
+
+# Function to find the repository root by searching for existing project markers
+find_repo_root() {
+    local dir="$1"
+    while [ "$dir" != "/" ]; do
+        if [ -d "$dir/.git" ] || [ -d "$dir/.specify" ]; then
+            echo "$dir"
+            return 0
+        fi
+        dir="$(dirname "$dir")"
+    done
+    return 1
+}
+
+# Function to get highest number from specs directory
+get_highest_from_specs() {
+    local specs_dir="$1"
+    local highest=0
+    
+    if [ -d "$specs_dir" ]; then
+        for dir in "$specs_dir"/*; do
+            [ -d "$dir" ] || continue
+            dirname=$(basename "$dir")
+            # Only match sequential prefixes (###-*), skip timestamp dirs
+            if echo "$dirname" | grep -q '^[0-9]\{3\}-'; then
+                number=$(echo "$dirname" | grep -o '^[0-9]\{3\}')
+                number=$((10#$number))
+                if [ "$number" -gt "$highest" ]; then
+                    highest=$number
+                fi
+            fi
+        done
+    fi
+    
+    echo "$highest"
+}
+
+# Function to get highest number from git branches
+get_highest_from_branches() {
+    local highest=0
+    
+    # Get all branches (local and remote)
+    branches=$(git branch -a 2>/dev/null || echo "")
+    
+    if [ -n "$branches" ]; then
+        while IFS= read -r branch; do
+            # Clean branch name: remove leading markers and remote prefixes
+            clean_branch=$(echo "$branch" | sed 's/^[* ]*//; s|^remotes/[^/]*/||')
+            
+            # Extract feature number if branch matches pattern ###-*
+            if echo "$clean_branch" | grep -q '^[0-9]\{3\}-'; then
+                number=$(echo "$clean_branch" | grep -o '^[0-9]\{3\}' || echo "0")
+                number=$((10#$number))
+                if [ "$number" -gt "$highest" ]; then
+                    highest=$number
+                fi
+            fi
+        done <<< "$branches"
+    fi
+    
+    echo "$highest"
+}
+
+# Function to check existing branches (local and remote) and return next available number
+check_existing_branches() {
+    local specs_dir="$1"
+
+    # Fetch all remotes to get latest branch info (suppress errors if no remotes)
+    git fetch --all --prune >/dev/null 2>&1 || true
+
+    # Get highest number from ALL branches (not just matching short name)
+    local highest_branch=$(get_highest_from_branches)
+
+    # Get highest number from ALL specs (not just matching short name)
+    local highest_spec=$(get_highest_from_specs "$specs_dir")
+
+    # Take the maximum of both
+    local max_num=$highest_branch
+    if [ "$highest_spec" -gt "$max_num" ]; then
+        max_num=$highest_spec
+    fi
+
+    # Return next number
+    echo $((max_num + 1))
+}
+
+# Function to clean and format a branch name
+clean_branch_name() {
+    local name="$1"
+    echo "$name" | tr '[:upper:]' '[:lower:]' | sed 's/[^a-z0-9]/-/g' | sed 's/-\+/-/g' | sed 's/^-//' | sed 's/-$//'
+}
+
+# Resolve repository root. Prefer git information when available, but fall back
+# to searching for repository markers so the workflow still functions in repositories that
+# were initialised with --no-git.
+SCRIPT_DIR="$(CDPATH="" cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+source "$SCRIPT_DIR/common.sh"
+
+if git rev-parse --show-toplevel >/dev/null 2>&1; then
+    REPO_ROOT=$(git rev-parse --show-toplevel)
+    HAS_GIT=true
+else
+    REPO_ROOT="$(find_repo_root "$SCRIPT_DIR")"
+    if [ -z "$REPO_ROOT" ]; then
+        echo "Error: Could not determine repository root. Please run this script from within the repository." >&2
+        exit 1
+    fi
+    HAS_GIT=false
+fi
+
+cd "$REPO_ROOT"
+
+SPECS_DIR="$REPO_ROOT/specs"
+mkdir -p "$SPECS_DIR"
+
+# Function to generate branch name with stop word filtering and length filtering
+generate_branch_name() {
+    local description="$1"
+    
+    # Common stop words to filter out
+    local stop_words="^(i|a|an|the|to|for|of|in|on|at|by|with|from|is|are|was|were|be|been|being|have|has|had|do|does|did|will|would|should|could|can|may|might|must|shall|this|that|these|those|my|your|our|their|want|need|add|get|set)$"
+    
+    # Convert to lowercase and split into words
+    local clean_name=$(echo "$description" | tr '[:upper:]' '[:lower:]' | sed 's/[^a-z0-9]/ /g')
+    
+    # Filter words: remove stop words and words shorter than 3 chars (unless they're uppercase acronyms in original)
+    local meaningful_words=()
+    for word in $clean_name; do
+        # Skip empty words
+        [ -z "$word" ] && continue
+        
+        # Keep words that are NOT stop words AND (length >= 3 OR are potential acronyms)
+        if ! echo "$word" | grep -qiE "$stop_words"; then
+            if [ ${#word} -ge 3 ]; then
+                meaningful_words+=("$word")
+            elif echo "$description" | grep -q "\b${word^^}\b"; then
+                # Keep short words if they appear as uppercase in original (likely acronyms)
+                meaningful_words+=("$word")
+            fi
+        fi
+    done
+    
+    # If we have meaningful words, use first 3-4 of them
+    if [ ${#meaningful_words[@]} -gt 0 ]; then
+        local max_words=3
+        if [ ${#meaningful_words[@]} -eq 4 ]; then max_words=4; fi
+        
+        local result=""
+        local count=0
+        for word in "${meaningful_words[@]}"; do
+            if [ $count -ge $max_words ]; then break; fi
+            if [ -n "$result" ]; then result="$result-"; fi
+            result="$result$word"
+            count=$((count + 1))
+        done
+        echo "$result"
+    else
+        # Fallback to original logic if no meaningful words found
+        local cleaned=$(clean_branch_name "$description")
+        echo "$cleaned" | tr '-' '\n' | grep -v '^$' | head -3 | tr '\n' '-' | sed 's/-$//'
+    fi
+}
+
+# Generate branch name
+if [ -n "$SHORT_NAME" ]; then
+    # Use provided short name, just clean it up
+    BRANCH_SUFFIX=$(clean_branch_name "$SHORT_NAME")
+else
+    # Generate from description with smart filtering
+    BRANCH_SUFFIX=$(generate_branch_name "$FEATURE_DESCRIPTION")
+fi
+
+# Warn if --number and --timestamp are both specified
+if [ "$USE_TIMESTAMP" = true ] && [ -n "$BRANCH_NUMBER" ]; then
+    >&2 echo "[specify] Warning: --number is ignored when --timestamp is used"
+    BRANCH_NUMBER=""
+fi
+
+# Determine branch prefix
+if [ "$USE_TIMESTAMP" = true ]; then
+    FEATURE_NUM=$(date +%Y%m%d-%H%M%S)
+    BRANCH_NAME="${FEATURE_NUM}-${BRANCH_SUFFIX}"
+else
+    # Determine branch number
+    if [ -z "$BRANCH_NUMBER" ]; then
+        if [ "$HAS_GIT" = true ]; then
+            # Check existing branches on remotes
+            BRANCH_NUMBER=$(check_existing_branches "$SPECS_DIR")
+        else
+            # Fall back to local directory check
+            HIGHEST=$(get_highest_from_specs "$SPECS_DIR")
+            BRANCH_NUMBER=$((HIGHEST + 1))
+        fi
+    fi
+
+    # Force base-10 interpretation to prevent octal conversion (e.g., 010 → 8 in octal, but should be 10 in decimal)
+    FEATURE_NUM=$(printf "%03d" "$((10#$BRANCH_NUMBER))")
+    BRANCH_NAME="${FEATURE_NUM}-${BRANCH_SUFFIX}"
+fi
+
+# GitHub enforces a 244-byte limit on branch names
+# Validate and truncate if necessary
+MAX_BRANCH_LENGTH=244
+if [ ${#BRANCH_NAME} -gt $MAX_BRANCH_LENGTH ]; then
+    # Calculate how much we need to trim from suffix
+    # Account for prefix length: timestamp (15) + hyphen (1) = 16, or sequential (3) + hyphen (1) = 4
+    PREFIX_LENGTH=$(( ${#FEATURE_NUM} + 1 ))
+    MAX_SUFFIX_LENGTH=$((MAX_BRANCH_LENGTH - PREFIX_LENGTH))
+    
+    # Truncate suffix at word boundary if possible
+    TRUNCATED_SUFFIX=$(echo "$BRANCH_SUFFIX" | cut -c1-$MAX_SUFFIX_LENGTH)
+    # Remove trailing hyphen if truncation created one
+    TRUNCATED_SUFFIX=$(echo "$TRUNCATED_SUFFIX" | sed 's/-$//')
+    
+    ORIGINAL_BRANCH_NAME="$BRANCH_NAME"
+    BRANCH_NAME="${FEATURE_NUM}-${TRUNCATED_SUFFIX}"
+    
+    >&2 echo "[specify] Warning: Branch name exceeded GitHub's 244-byte limit"
+    >&2 echo "[specify] Original: $ORIGINAL_BRANCH_NAME (${#ORIGINAL_BRANCH_NAME} bytes)"
+    >&2 echo "[specify] Truncated to: $BRANCH_NAME (${#BRANCH_NAME} bytes)"
+fi
+
+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
+                >&2 echo "Error: Branch '$BRANCH_NAME' already exists. Rerun to get a new timestamp or use a different --short-name."
+            else
+                >&2 echo "Error: Branch '$BRANCH_NAME' already exists. Please use a different feature name or specify a different number with --number."
+            fi
+            exit 1
+        else
+            >&2 echo "Error: Failed to create git branch '$BRANCH_NAME'. Please check your git configuration and try again."
+            exit 1
+        fi
+    fi
+else
+    >&2 echo "[specify] Warning: Git repository not detected; skipped branch creation for $BRANCH_NAME"
+fi
+
+FEATURE_DIR="$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"
+fi
+
+# Inform the user how to persist the feature variable in their own shell
+printf '# To persist: export SPECIFY_FEATURE=%q\n' "$BRANCH_NAME" >&2
+
+if $JSON_MODE; then
+    if command -v jq >/dev/null 2>&1; then
+        jq -cn \
+            --arg branch_name "$BRANCH_NAME" \
+            --arg spec_file "$SPEC_FILE" \
+            --arg feature_num "$FEATURE_NUM" \
+            '{BRANCH_NAME:$branch_name,SPEC_FILE:$spec_file,FEATURE_NUM:$feature_num}'
+    else
+        printf '{"BRANCH_NAME":"%s","SPEC_FILE":"%s","FEATURE_NUM":"%s"}\n' "$(json_escape "$BRANCH_NAME")" "$(json_escape "$SPEC_FILE")" "$(json_escape "$FEATURE_NUM")"
+    fi
+else
+    echo "BRANCH_NAME: $BRANCH_NAME"
+    echo "SPEC_FILE: $SPEC_FILE"
+    echo "FEATURE_NUM: $FEATURE_NUM"
+    printf '# To persist in your shell: export SPECIFY_FEATURE=%q\n' "$BRANCH_NAME"
+fi

extensions/git/scripts/bash/git-common.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+# Git-specific common functions for the git extension.
+# Extracted from scripts/bash/common.sh — contains only git-specific
+# branch validation and detection logic.
+
+# Check if we have git available
+has_git() {
+    git rev-parse --show-toplevel >/dev/null 2>&1
+}
+
+# Validate that a branch name matches the expected feature branch pattern.
+# Accepts sequential (###-*) or timestamp (YYYYMMDD-HHMMSS-*) formats.
+check_feature_branch() {
+    local branch="$1"
+    local has_git_repo="$2"
+
+    # For non-git repos, we can't enforce branch naming but still provide output
+    if [[ "$has_git_repo" != "true" ]]; then
+        echo "[specify] Warning: Git repository not detected; skipped branch validation" >&2
+        return 0
+    fi
+
+    if [[ ! "$branch" =~ ^[0-9]{3}- ]] && [[ ! "$branch" =~ ^[0-9]{8}-[0-9]{6}- ]]; then
+        echo "ERROR: Not on a feature branch. Current branch: $branch" >&2
+        echo "Feature branches should be named like: 001-feature-name or 20260319-143022-feature-name" >&2
+        return 1
+    fi
+
+    return 0
+}

extensions/git/scripts/powershell/create-new-feature.ps1

@@ -0,0 +1,329 @@
+#!/usr/bin/env pwsh
+# Create a new feature
+[CmdletBinding()]
+param(
+    [switch]$Json,
+    [string]$ShortName,
+    [Parameter()]
+    [int]$Number = 0,
+    [switch]$Timestamp,
+    [switch]$Help,
+    [Parameter(Position = 0, ValueFromRemainingArguments = $true)]
+    [string[]]$FeatureDescription
+)
+$ErrorActionPreference = 'Stop'
+
+# Show help if requested
+if ($Help) {
+    Write-Host "Usage: ./create-new-feature.ps1 [-Json] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
+    Write-Host ""
+    Write-Host "Options:"
+    Write-Host "  -Json               Output in JSON format"
+    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"
+    Write-Host "  -Help               Show this help message"
+    Write-Host ""
+    Write-Host "Examples:"
+    Write-Host "  ./create-new-feature.ps1 'Add user authentication system' -ShortName 'user-auth'"
+    Write-Host "  ./create-new-feature.ps1 'Implement OAuth2 integration for API'"
+    Write-Host "  ./create-new-feature.ps1 -Timestamp -ShortName 'user-auth' 'Add user authentication'"
+    exit 0
+}
+
+# Check if feature description provided
+if (-not $FeatureDescription -or $FeatureDescription.Count -eq 0) {
+    Write-Error "Usage: ./create-new-feature.ps1 [-Json] [-ShortName <name>] [-Number N] [-Timestamp] <feature description>"
+    exit 1
+}
+
+$featureDesc = ($FeatureDescription -join ' ').Trim()
+
+# Validate description is not empty after trimming (e.g., user passed only whitespace)
+if ([string]::IsNullOrWhiteSpace($featureDesc)) {
+    Write-Error "Error: Feature description cannot be empty or contain only whitespace"
+    exit 1
+}
+
+# Resolve repository root. Prefer git information when available, but fall back
+# to searching for repository markers so the workflow still functions in repositories that
+# were initialized with --no-git.
+function Find-RepositoryRoot {
+    param(
+        [string]$StartDir,
+        [string[]]$Markers = @('.git', '.specify')
+    )
+    $current = Resolve-Path $StartDir
+    while ($true) {
+        foreach ($marker in $Markers) {
+            if (Test-Path (Join-Path $current $marker)) {
+                return $current
+            }
+        }
+        $parent = Split-Path $current -Parent
+        if ($parent -eq $current) {
+            # Reached filesystem root without finding markers
+            return $null
+        }
+        $current = $parent
+    }
+}
+
+function Get-HighestNumberFromSpecs {
+    param([string]$SpecsDir)
+    
+    $highest = 0
+    if (Test-Path $SpecsDir) {
+        Get-ChildItem -Path $SpecsDir -Directory | ForEach-Object {
+            if ($_.Name -match '^(\d{3})-') {
+                $num = [int]$matches[1]
+                if ($num -gt $highest) { $highest = $num }
+            }
+        }
+    }
+    return $highest
+}
+
+function Get-HighestNumberFromBranches {
+    param()
+    
+    $highest = 0
+    try {
+        $branches = git branch -a 2>$null
+        if ($LASTEXITCODE -eq 0) {
+            foreach ($branch in $branches) {
+                # Clean branch name: remove leading markers and remote prefixes
+                $cleanBranch = $branch.Trim() -replace '^\*?\s+', '' -replace '^remotes/[^/]+/', ''
+                
+                # Extract feature number if branch matches pattern ###-*
+                if ($cleanBranch -match '^(\d{3})-') {
+                    $num = [int]$matches[1]
+                    if ($num -gt $highest) { $highest = $num }
+                }
+            }
+        }
+    } catch {
+        # If git command fails, return 0
+        Write-Verbose "Could not check Git branches: $_"
+    }
+    return $highest
+}
+
+function Get-NextBranchNumber {
+    param(
+        [string]$SpecsDir
+    )
+
+    # Fetch all remotes to get latest branch info (suppress errors if no remotes)
+    try {
+        git fetch --all --prune 2>$null | Out-Null
+    } catch {
+        # Ignore fetch errors
+    }
+
+    # Get highest number from ALL branches (not just matching short name)
+    $highestBranch = Get-HighestNumberFromBranches
+
+    # Get highest number from ALL specs (not just matching short name)
+    $highestSpec = Get-HighestNumberFromSpecs -SpecsDir $SpecsDir
+
+    # Take the maximum of both
+    $maxNum = [Math]::Max($highestBranch, $highestSpec)
+
+    # Return next number
+    return $maxNum + 1
+}
+
+function ConvertTo-CleanBranchName {
+    param([string]$Name)
+    
+    return $Name.ToLower() -replace '[^a-z0-9]', '-' -replace '-{2,}', '-' -replace '^-', '' -replace '-$', ''
+}
+$fallbackRoot = (Find-RepositoryRoot -StartDir $PSScriptRoot)
+if (-not $fallbackRoot) {
+    Write-Error "Error: Could not determine repository root. Please run this script from within the repository."
+    exit 1
+}
+
+# Load common functions (includes Resolve-Template)
+. "$PSScriptRoot/common.ps1"
+
+try {
+    $repoRoot = git rev-parse --show-toplevel 2>$null
+    if ($LASTEXITCODE -eq 0) {
+        $hasGit = $true
+    } else {
+        throw "Git not available"
+    }
+} catch {
+    $repoRoot = $fallbackRoot
+    $hasGit = $false
+}
+
+Set-Location $repoRoot
+
+$specsDir = Join-Path $repoRoot 'specs'
+New-Item -ItemType Directory -Path $specsDir -Force | Out-Null
+
+# Function to generate branch name with stop word filtering and length filtering
+function Get-BranchName {
+    param([string]$Description)
+    
+    # Common stop words to filter out
+    $stopWords = @(
+        'i', 'a', 'an', 'the', 'to', 'for', 'of', 'in', 'on', 'at', 'by', 'with', 'from',
+        'is', 'are', 'was', 'were', 'be', 'been', 'being', 'have', 'has', 'had',
+        'do', 'does', 'did', 'will', 'would', 'should', 'could', 'can', 'may', 'might', 'must', 'shall',
+        'this', 'that', 'these', 'those', 'my', 'your', 'our', 'their',
+        'want', 'need', 'add', 'get', 'set'
+    )
+    
+    # Convert to lowercase and extract words (alphanumeric only)
+    $cleanName = $Description.ToLower() -replace '[^a-z0-9\s]', ' '
+    $words = $cleanName -split '\s+' | Where-Object { $_ }
+    
+    # Filter words: remove stop words and words shorter than 3 chars (unless they're uppercase acronyms in original)
+    $meaningfulWords = @()
+    foreach ($word in $words) {
+        # Skip stop words
+        if ($stopWords -contains $word) { continue }
+        
+        # Keep words that are length >= 3 OR appear as uppercase in original (likely acronyms)
+        if ($word.Length -ge 3) {
+            $meaningfulWords += $word
+        } elseif ($Description -match "\b$($word.ToUpper())\b") {
+            # Keep short words if they appear as uppercase in original (likely acronyms)
+            $meaningfulWords += $word
+        }
+    }
+    
+    # If we have meaningful words, use first 3-4 of them
+    if ($meaningfulWords.Count -gt 0) {
+        $maxWords = if ($meaningfulWords.Count -eq 4) { 4 } else { 3 }
+        $result = ($meaningfulWords | Select-Object -First $maxWords) -join '-'
+        return $result
+    } else {
+        # Fallback to original logic if no meaningful words found
+        $result = ConvertTo-CleanBranchName -Name $Description
+        $fallbackWords = ($result -split '-') | Where-Object { $_ } | Select-Object -First 3
+        return [string]::Join('-', $fallbackWords)
+    }
+}
+
+# Generate branch name
+if ($ShortName) {
+    # Use provided short name, just clean it up
+    $branchSuffix = ConvertTo-CleanBranchName -Name $ShortName
+} else {
+    # Generate from description with smart filtering
+    $branchSuffix = Get-BranchName -Description $featureDesc
+}
+
+# Warn if -Number and -Timestamp are both specified
+if ($Timestamp -and $Number -ne 0) {
+    Write-Warning "[specify] Warning: -Number is ignored when -Timestamp is used"
+    $Number = 0
+}
+
+# Determine branch prefix
+if ($Timestamp) {
+    $featureNum = Get-Date -Format 'yyyyMMdd-HHmmss'
+    $branchName = "$featureNum-$branchSuffix"
+} else {
+    # Determine branch number
+    if ($Number -eq 0) {
+        if ($hasGit) {
+            # Check existing branches on remotes
+            $Number = Get-NextBranchNumber -SpecsDir $specsDir
+        } else {
+            # Fall back to local directory check
+            $Number = (Get-HighestNumberFromSpecs -SpecsDir $specsDir) + 1
+        }
+    }
+
+    $featureNum = ('{0:000}' -f $Number)
+    $branchName = "$featureNum-$branchSuffix"
+}
+
+# GitHub enforces a 244-byte limit on branch names
+# Validate and truncate if necessary
+$maxBranchLength = 244
+if ($branchName.Length -gt $maxBranchLength) {
+    # Calculate how much we need to trim from suffix
+    # Account for prefix length: timestamp (15) + hyphen (1) = 16, or sequential (3) + hyphen (1) = 4
+    $prefixLength = $featureNum.Length + 1
+    $maxSuffixLength = $maxBranchLength - $prefixLength
+    
+    # Truncate suffix
+    $truncatedSuffix = $branchSuffix.Substring(0, [Math]::Min($branchSuffix.Length, $maxSuffixLength))
+    # Remove trailing hyphen if truncation created one
+    $truncatedSuffix = $truncatedSuffix -replace '-$', ''
+    
+    $originalBranchName = $branchName
+    $branchName = "$featureNum-$truncatedSuffix"
+    
+    Write-Warning "[specify] Branch name exceeded GitHub's 244-byte limit"
+    Write-Warning "[specify] Original: $originalBranchName ($($originalBranchName.Length) bytes)"
+    Write-Warning "[specify] Truncated to: $branchName ($($branchName.Length) bytes)"
+}
+
+if ($hasGit) {
+    $branchCreated = $false
+    try {
+        git checkout -q -b $branchName 2>$null | Out-Null
+        if ($LASTEXITCODE -eq 0) {
+            $branchCreated = $true
+        }
+    } catch {
+        # Exception during git command
+    }
+
+    if (-not $branchCreated) {
+        # Check if branch already exists
+        $existingBranch = git branch --list $branchName 2>$null
+        if ($existingBranch) {
+            if ($Timestamp) {
+                Write-Error "Error: Branch '$branchName' already exists. Rerun to get a new timestamp or use a different -ShortName."
+            } else {
+                Write-Error "Error: Branch '$branchName' already exists. Please use a different feature name or specify a different number with -Number."
+            }
+            exit 1
+        } else {
+            Write-Error "Error: Failed to create git branch '$branchName'. Please check your git configuration and try again."
+            exit 1
+        }
+    }
+} else {
+    Write-Warning "[specify] Warning: Git repository not detected; skipped branch creation for $branchName"
+}
+
+$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 $specFile | Out-Null 
+}
+
+# Set the SPECIFY_FEATURE environment variable for the current session
+$env:SPECIFY_FEATURE = $branchName
+
+if ($Json) {
+    $obj = [PSCustomObject]@{ 
+        BRANCH_NAME = $branchName
+        SPEC_FILE = $specFile
+        FEATURE_NUM = $featureNum
+        HAS_GIT = $hasGit
+    }
+    $obj | ConvertTo-Json -Compress
+} else {
+    Write-Output "BRANCH_NAME: $branchName"
+    Write-Output "SPEC_FILE: $specFile"
+    Write-Output "FEATURE_NUM: $featureNum"
+    Write-Output "HAS_GIT: $hasGit"
+    Write-Output "SPECIFY_FEATURE environment variable set to: $branchName"
+}
+

extensions/git/scripts/powershell/git-common.ps1

@@ -0,0 +1,33 @@
+#!/usr/bin/env pwsh
+# Git-specific common functions for the git extension.
+# Extracted from scripts/powershell/common.ps1 — contains only git-specific
+# branch validation and detection logic.
+
+function Test-HasGit {
+    try {
+        git rev-parse --show-toplevel 2>$null | Out-Null
+        return ($LASTEXITCODE -eq 0)
+    } catch {
+        return $false
+    }
+}
+
+function Test-FeatureBranch {
+    param(
+        [string]$Branch,
+        [bool]$HasGit = $true
+    )
+    
+    # For non-git repos, we can't enforce branch naming but still provide output
+    if (-not $HasGit) {
+        Write-Warning "[specify] Warning: Git repository not detected; skipped branch validation"
+        return $true
+    }
+    
+    if ($Branch -notmatch '^[0-9]{3}-' -and $Branch -notmatch '^\d{8}-\d{6}-') {
+        Write-Output "ERROR: Not on a feature branch. Current branch: $Branch"
+        Write-Output "Feature branches should be named like: 001-feature-name or 20260319-143022-feature-name"
+        return $false
+    }
+    return $true
+}

pyproject.toml

@@ -41,6 +41,7 @@ packages = ["src/specify_cli"]
 "templates/commands" = "specify_cli/core_pack/commands"
 "scripts/bash" = "specify_cli/core_pack/scripts/bash"
 "scripts/powershell" = "specify_cli/core_pack/scripts/powershell"
+"extensions/git" = "specify_cli/core_pack/extensions/git"
 ".github/workflows/scripts/create-release-packages.sh" = "specify_cli/core_pack/release_scripts/create-release-packages.sh"
 ".github/workflows/scripts/create-release-packages.ps1" = "specify_cli/core_pack/release_scripts/create-release-packages.ps1"
 

src/specify_cli/__init__.py

@@ -1159,6 +1159,57 @@ def _locate_core_pack() -> Path | None:
     return None
 
 
+def _locate_bundled_git_extension() -> Path | None:
+    """Return the path to the bundled git extension, or None.
+
+    Checks the wheel's core_pack first, then falls back to the
+    source-checkout ``extensions/git/`` directory.
+    """
+    core = _locate_core_pack()
+    if core is not None:
+        candidate = core / "extensions" / "git"
+        if (candidate / "extension.yml").is_file():
+            return candidate
+
+    # Source-checkout / editable install: look relative to repo root
+    repo_root = Path(__file__).parent.parent.parent
+    candidate = repo_root / "extensions" / "git"
+    if (candidate / "extension.yml").is_file():
+        return candidate
+
+    return None
+
+
+def _install_bundled_git_extension(project_path: Path) -> bool:
+    """Auto-install the bundled git extension during ``specify init``.
+
+    This is a migration-period mechanism (pre-1.0.0) that auto-enables
+    the git extension so that existing branching workflows continue to work.
+    Before 1.0.0, this auto-install will be removed and the extension will
+    become opt-in.
+
+    Returns True if the extension was installed, False otherwise.
+    """
+    ext_source = _locate_bundled_git_extension()
+    if ext_source is None:
+        return False
+
+    try:
+        from .extensions import ExtensionManager, ExtensionError
+        manager = ExtensionManager(project_path)
+
+        # Skip if already installed (e.g. via preset)
+        if manager.registry.is_installed("git"):
+            return True
+
+        speckit_ver = get_speckit_version()
+        manager.install_from_directory(ext_source, speckit_ver)
+        return True
+    except Exception:
+        # Non-fatal: branching still works via core scripts during migration
+        return False
+
+
 def _locate_release_script() -> tuple[Path, str]:
     """Return (script_path, shell_cmd) for the platform-appropriate release script.
 
@@ -2176,6 +2227,11 @@ def init(
                 "speckit_version": get_speckit_version(),
             })
 
+            # Auto-install the bundled git extension (migration period, pre-1.0.0).
+            # This preserves backward compatibility for existing branching workflows.
+            # Before 1.0.0, this will be removed and git becomes opt-in.
+            _install_bundled_git_extension(project_path)
+
             # Install preset if specified
             if preset:
                 try:

templates/commands/specify.md

@@ -75,10 +75,23 @@ Given that feature description, do this:
 
 2. **Create the feature branch** by running the script with `--short-name` (and `--json`). In sequential mode, do NOT pass `--number` — the script auto-detects the next available number. In timestamp mode, the script generates a `YYYYMMDD-HHMMSS` prefix automatically:
 
-   **Branch numbering mode**: Before running the script, check if `.specify/init-options.json` exists and read the `branch_numbering` value.
+   **Git extension check**: Before running the branch creation script, check if the git extension is enabled:
+   - Check if `.specify/extensions/.registry/git.json` exists
+   - If it exists, read it and verify `"enabled"` is `true` (or not explicitly set to `false`)
+   - If the git extension is **disabled** or the registry file does not exist, **skip branch creation entirely** — proceed directly to step 3 using a spec directory name derived from the short name (e.g., `specs/<short-name>/`)
+   - If the git extension is enabled (or the registry file doesn't exist but `.specify/init-options.json` has `branch_numbering` set), proceed with branch creation below
+
+   **Branch numbering mode**: Before running the script, determine the branch numbering strategy:
+   1. Check `.specify/extensions/git/git-config.yml` for `branch_numbering` value (extension config takes precedence)
+   2. If not found, check `.specify/init-options.json` for `branch_numbering` value (backward compatibility)
+   3. Default to `sequential` if neither exists
    - If `"timestamp"`, add `--timestamp` (Bash) or `-Timestamp` (PowerShell) to the script invocation
    - If `"sequential"` or absent, do not add any extra flag (default behavior)
 
+   **Script resolution**: Use the extension's bundled scripts when available, falling back to core scripts:
+   - If `.specify/extensions/git/scripts/bash/create-new-feature.sh` exists, use it
+   - Otherwise, fall back to `{SCRIPT}`
+
    - Bash example: `{SCRIPT} --json --short-name "user-auth" "Add user authentication"`
    - Bash (timestamp): `{SCRIPT} --json --timestamp --short-name "user-auth" "Add user authentication"`
    - PowerShell example: `{SCRIPT} -Json -ShortName "user-auth" "Add user authentication"`