fix(git-extension): avoid shell interpolation of generated commit messages

- Remove 	r -d '[:space:]' from commit_style parsing in auto-commit.sh:
  it stripped ALL whitespace (not just leading/trailing), so
  commit_style: con ventional was silently normalized to conventional
  instead of being rejected as unknown (PowerShell version already
  rejected it correctly).
- Add a file-based message-passing channel to both auto-commit scripts:
  --message-file <path> (bash) / -MessageFile <path> (PowerShell).
  Agent-generated commit messages may contain quotes, $(...), or
  backticks; passing them as a shell argument risked command injection
  if ever inlined into a shell command string. The new flag reads the
  message from a file instead, so untrusted content never touches a
  shell command line. The raw positional-argument form is kept for
  backward compatibility.
- Update speckit.git.commit.md to instruct the agent to write the
  generated message to a temp file (via its file-editing tool) and pass
  the file path, explicitly warning against inlining the message into a
  shell command string.
- Add test coverage: explicit commit_style: fixed (previously only the
  absent-key default was tested), --message-file/-MessageFile success
  path (including injection-shaped content), and missing-file error path,
  for both bash and PowerShell suites.

Assisted-by: GitHub Copilot (model: claude-sonnet-5, autonomous)
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: dhruv-15-03

extensions/git/commands/speckit.git.commit.md

@@ -22,18 +22,18 @@ This command is invoked as a hook after (or before) core commands. It:
 Controlled by the `commit_style` key in `.specify/extensions/git/git-config.yml`:
 
 - **`fixed`** (default): use the per-command `message` if configured, otherwise a generic `[Spec Kit] Auto-commit <phase> <command>` message.
-- **`conventional`**: inspect the actual changes (`git diff` / `git status`) since the last commit and generate a single-line [Conventional Commit](https://www.conventionalcommits.org/) message (`type(scope): subject`, e.g. `feat: add OAuth specification` or `docs: update implementation plan`) that accurately summarizes the change. Pass this message as the script's second argument. The configured `message` values are ignored in this mode.
+- **`conventional`**: inspect the actual changes (`git diff` / `git status`) since the last commit and generate a single-line [Conventional Commit](https://www.conventionalcommits.org/) message (`type(scope): subject`, e.g. `feat: add OAuth specification` or `docs: update implementation plan`) that accurately summarizes the change. Write this message to a temporary file and pass the file's path to the script (see Execution below). The configured `message` values are ignored in this mode.
 
 ## Execution
 
 Determine the event name from the hook that triggered this command, then run the script:
 
-- **Bash**: `.specify/extensions/git/scripts/bash/auto-commit.sh <event_name> ["<generated_message>"]`
-- **PowerShell**: `.specify/extensions/git/scripts/powershell/auto-commit.ps1 <event_name> ["<generated_message>"]`
+- **Bash**: `.specify/extensions/git/scripts/bash/auto-commit.sh <event_name> [--message-file <path>]`
+- **PowerShell**: `.specify/extensions/git/scripts/powershell/auto-commit.ps1 <event_name> [-MessageFile <path>]`
 
-Replace `<event_name>` with the actual hook event (e.g., `after_specify`, `before_plan`, `after_implement`). Only pass `<generated_message>` when `commit_style: conventional` is configured — first check `.specify/extensions/git/git-config.yml` for the value of `commit_style`:
+Replace `<event_name>` with the actual hook event (e.g., `after_specify`, `before_plan`, `after_implement`). Only pass a generated message when `commit_style: conventional` is configured — first check `.specify/extensions/git/git-config.yml` for the value of `commit_style`:
 
-- If `conventional`: inspect the diff, generate a Conventional Commit message, and pass it as the second argument.
+- If `conventional`: inspect the diff and generate a Conventional Commit message. **Do not interpolate the generated message directly into a shell command string** — its content is derived from repository changes and may contain characters (quotes, `$(...)`, backticks) that a shell would execute or that would break command quoting. Instead, write the message to a temporary file using your file-editing tool (not a shell `echo`/`printf`), then pass that file's path via `--message-file <path>` (Bash) or `-MessageFile <path>` (PowerShell).
 - If `fixed` or absent: run the script with just `<event_name>`; it uses the configured/static message.
 
 ## Configuration

extensions/git/scripts/bash/auto-commit.sh

@@ -4,20 +4,49 @@
 # Checks per-command config keys in git-config.yml before committing.
 #
 # Usage: auto-commit.sh <event_name> [generated_message]
+#        auto-commit.sh <event_name> --message-file <path>
 #   e.g.: auto-commit.sh after_specify
-#   e.g.: auto-commit.sh after_specify "feat: add OAuth specification"  (commit_style: conventional)
+#   e.g.: auto-commit.sh after_specify --message-file /tmp/commit-msg.txt  (commit_style: conventional)
+#
+# --message-file is the preferred way to supply an agent-generated commit
+# message: it reads the message from a file instead of a shell argument,
+# so message content (which may contain quotes, `$(...)`, backticks, etc.)
+# is never interpolated into a shell command line.
 
 set -e
 
 EVENT_NAME="${1:-}"
 if [ -z "$EVENT_NAME" ]; then
-    echo "Usage: $0 <event_name> [generated_message]" >&2
+    echo "Usage: $0 <event_name> [generated_message | --message-file <path>]" >&2
     exit 1
 fi
+shift || true
 
 # Optional second argument: an agent-generated commit message (used when
-# commit_style: conventional is configured).
-GENERATED_MESSAGE="${2:-}"
+# commit_style: conventional is configured). Prefer --message-file over
+# passing the message directly as a shell argument.
+GENERATED_MESSAGE=""
+while [ $# -gt 0 ]; do
+    case "$1" in
+        --message-file)
+            _message_file="${2:-}"
+            if [ -z "$_message_file" ]; then
+                echo "[specify] Error: --message-file requires a path argument" >&2
+                exit 1
+            fi
+            if [ ! -f "$_message_file" ]; then
+                echo "[specify] Error: message file '$_message_file' not found" >&2
+                exit 1
+            fi
+            GENERATED_MESSAGE="$(cat "$_message_file")"
+            shift 2
+            ;;
+        *)
+            GENERATED_MESSAGE="$1"
+            shift
+            ;;
+    esac
+done
 
 SCRIPT_DIR="$(CDPATH="" cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
@@ -55,7 +84,7 @@ _commit_style="fixed"
 
 if [ -f "$_config_file" ]; then
     # Top-level scalar key: commit_style (fixed | conventional)
-    _style_val=$(grep -m1 '^commit_style:' "$_config_file" 2>/dev/null | sed 's/^commit_style:[[:space:]]*//' | sed 's/[[:space:]]\{1,\}#.*$//' | sed 's/[[:space:]]*$//' | sed 's/^["'\'']//' | sed 's/["'\'']*$//' | tr -d '[:space:]' | tr '[:upper:]' '[:lower:]')
+    _style_val=$(grep -m1 '^commit_style:' "$_config_file" 2>/dev/null | sed 's/^commit_style:[[:space:]]*//' | sed 's/[[:space:]]\{1,\}#.*$//' | sed 's/[[:space:]]*$//' | sed 's/^["'\'']//' | sed 's/["'\'']*$//' | tr '[:upper:]' '[:lower:]')
     if [ -n "$_style_val" ]; then
         case "$_style_val" in
             fixed|conventional)
@@ -148,7 +177,7 @@ if [ "$_commit_style" = "conventional" ]; then
     if [ -n "$GENERATED_MESSAGE" ]; then
         _commit_msg="$GENERATED_MESSAGE"
     else
-        echo "[specify] Error: commit_style is 'conventional' but no generated commit message was supplied; aborting auto-commit (pass the generated message as arg 2, or set commit_style: fixed)" >&2
+        echo "[specify] Error: commit_style is 'conventional' but no generated commit message was supplied; aborting auto-commit (pass --message-file <path>, or a raw message as arg 2, or set commit_style: fixed)" >&2
         exit 1
     fi
 fi

extensions/git/scripts/powershell/auto-commit.ps1

@@ -4,18 +4,39 @@
 # Checks per-command config keys in git-config.yml before committing.
 #
 # Usage: auto-commit.ps1 <event_name> [generated_message]
+#        auto-commit.ps1 <event_name> -MessageFile <path>
 #   e.g.: auto-commit.ps1 after_specify
-#   e.g.: auto-commit.ps1 after_specify "feat: add OAuth specification"  (commit_style: conventional)
+#   e.g.: auto-commit.ps1 after_specify -MessageFile C:\temp\commit-msg.txt  (commit_style: conventional)
+#
+# -MessageFile is the preferred way to supply an agent-generated commit
+# message: it reads the message from a file instead of a shell argument,
+# so message content (which may contain quotes, $(...), backticks, etc.)
+# is never interpolated into a shell command line.
 param(
     [Parameter(Position = 0, Mandatory = $true)]
     [string]$EventName,
 
     # Optional agent-generated commit message (used when commit_style: conventional is configured).
+    # Prefer -MessageFile over passing the message directly as a shell argument.
     [Parameter(Position = 1, Mandatory = $false)]
-    [string]$GeneratedMessage = ""
+    [string]$GeneratedMessage = "",
+
+    [Parameter(Mandatory = $false)]
+    [string]$MessageFile = ""
 )
 $ErrorActionPreference = 'Stop'
 
+if ($MessageFile) {
+    if (-not (Test-Path $MessageFile -PathType Leaf)) {
+        Write-Warning "[specify] Error: message file '$MessageFile' not found"
+        exit 1
+    }
+    $GeneratedMessage = (Get-Content -Path $MessageFile -Raw)
+    if ($null -ne $GeneratedMessage) {
+        $GeneratedMessage = $GeneratedMessage.TrimEnd("`r", "`n")
+    }
+}
+
 function Find-ProjectRoot {
     param([string]$StartDir)
     $current = Resolve-Path $StartDir
@@ -168,7 +189,7 @@ if ($commitStyle -eq 'conventional') {
     if ($GeneratedMessage) {
         $commitMsg = $GeneratedMessage
     } else {
-        Write-Warning "[specify] Error: commit_style is 'conventional' but no generated commit message was supplied; aborting auto-commit (pass the generated message as arg 2, or set commit_style: fixed)"
+        Write-Warning "[specify] Error: commit_style is 'conventional' but no generated commit message was supplied; aborting auto-commit (pass -MessageFile <path>, or a raw message as arg 2, or set commit_style: fixed)"
         exit 1
     }
 }

tests/extensions/git/test_git_extension.py

@@ -1114,6 +1114,73 @@ def test_fixed_is_default_when_commit_style_absent(self, tmp_path: Path):
         )
         assert "[Spec Kit] Add specification" in log.stdout
 
+    def test_explicit_fixed_style_uses_configured_message(self, tmp_path: Path):
+        """commit_style: fixed (explicit) still uses the configured static message,
+        not just the absent-key default."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: fixed\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+            '    message: "[Spec Kit] Add specification"\n'
+        ))
+        (project / "new-file.txt").write_text("content")
+        result = _run_bash(
+            "auto-commit.sh", project, "after_specify", "feat: this should be ignored"
+        )
+        assert result.returncode == 0
+        log = subprocess.run(
+            ["git", "log", "--oneline", "-1"],
+            cwd=project, capture_output=True, text=True,
+        )
+        assert "[Spec Kit] Add specification" in log.stdout
+        assert "this should be ignored" not in log.stdout
+
+    def test_conventional_message_file_used(self, tmp_path: Path):
+        """--message-file reads the generated message from a file instead of argv,
+        avoiding shell interpolation of agent-controlled content."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: conventional\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+            '    message: "[Spec Kit] Add specification"\n'
+        ))
+        (project / "new-file.txt").write_text("content")
+        msg_file = tmp_path / "commit-msg.txt"
+        msg_file.write_text("feat: add $(dangerous) `injection` test\n")
+        result = _run_bash(
+            "auto-commit.sh", project, "after_specify", "--message-file", str(msg_file)
+        )
+        assert result.returncode == 0
+        log = subprocess.run(
+            ["git", "log", "--oneline", "-1"],
+            cwd=project, capture_output=True, text=True,
+        )
+        assert "feat: add $(dangerous) `injection` test" in log.stdout
+
+    def test_message_file_missing_fails(self, tmp_path: Path):
+        """--message-file pointing at a nonexistent file fails clearly."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: conventional\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+        ))
+        (project / "new-file.txt").write_text("content")
+        missing = tmp_path / "does-not-exist.txt"
+        result = _run_bash(
+            "auto-commit.sh", project, "after_specify", "--message-file", str(missing)
+        )
+        assert result.returncode != 0
+        assert "not found" in result.stderr.lower()
+
     def test_conventional_uses_generated_message(self, tmp_path: Path):
         """commit_style: conventional uses the generated_message argument as the commit message."""
         project = _setup_project(tmp_path)
@@ -1332,6 +1399,73 @@ def test_fixed_is_default_when_commit_style_absent(self, tmp_path: Path):
         )
         assert "[Spec Kit] Add specification" in log.stdout
 
+    def test_explicit_fixed_style_uses_configured_message(self, tmp_path: Path):
+        """commit_style: fixed (explicit) still uses the configured static message,
+        not just the absent-key default."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: fixed\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+            '    message: "[Spec Kit] Add specification"\n'
+        ))
+        (project / "new-file.txt").write_text("content")
+        result = _run_pwsh(
+            "auto-commit.ps1", project, "after_specify", "feat: this should be ignored"
+        )
+        assert result.returncode == 0
+        log = subprocess.run(
+            ["git", "log", "--oneline", "-1"],
+            cwd=project, capture_output=True, text=True,
+        )
+        assert "[Spec Kit] Add specification" in log.stdout
+        assert "this should be ignored" not in log.stdout
+
+    def test_conventional_message_file_used(self, tmp_path: Path):
+        """-MessageFile reads the generated message from a file instead of argv,
+        avoiding shell interpolation of agent-controlled content."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: conventional\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+            '    message: "[Spec Kit] Add specification"\n'
+        ))
+        (project / "new-file.txt").write_text("content")
+        msg_file = tmp_path / "commit-msg.txt"
+        msg_file.write_text("feat: add $(dangerous) `injection` test\n")
+        result = _run_pwsh(
+            "auto-commit.ps1", project, "after_specify", "-MessageFile", str(msg_file)
+        )
+        assert result.returncode == 0
+        log = subprocess.run(
+            ["git", "log", "--oneline", "-1"],
+            cwd=project, capture_output=True, text=True,
+        )
+        assert "feat: add $(dangerous) `injection` test" in log.stdout
+
+    def test_message_file_missing_fails(self, tmp_path: Path):
+        """-MessageFile pointing at a nonexistent file fails clearly."""
+        project = _setup_project(tmp_path)
+        _write_config(project, (
+            "commit_style: conventional\n"
+            "auto_commit:\n"
+            "  default: false\n"
+            "  after_specify:\n"
+            "    enabled: true\n"
+        ))
+        (project / "new-file.txt").write_text("content")
+        missing = tmp_path / "does-not-exist.txt"
+        result = _run_pwsh(
+            "auto-commit.ps1", project, "after_specify", "-MessageFile", str(missing)
+        )
+        assert result.returncode != 0
+        assert "not found" in (result.stdout + result.stderr).lower()
+
     def test_conventional_uses_generated_message(self, tmp_path: Path):
         """commit_style: conventional uses the generated_message argument as the commit message."""
         project = _setup_project(tmp_path)