Add commit message normalizer

CLAUDE.md

@@ -27,20 +27,20 @@ Use `td usage -q` after first read.
 ```bash
 go build -o td .           # Build locally
 go test ./...              # Test all
+make install-hooks         # Install pre-commit + commit-msg hooks
 ```
 
 ## Version & Release
 
 ```bash
-# Commit changes with proper message
-git add .
-git commit -m "feat: description of changes
-
-Details here
+# Install the local hooks once per clone
+make install-hooks
 
-🤖 Generated with Claude Code
-
-Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>"
+# Commit changes with the normalized td subject
+git add .
+git commit \
+  -m "$(td commit-message 'describe changes')" \
+  -m "Details here"
 
 # Create version tag (bump from current version, e.g., v0.2.0 → v0.3.0)
 git tag -a v0.3.0 -m "Release v0.3.0: description"

Makefile

@@ -13,7 +13,7 @@ help:
 	@printf "%s\n" \
 		"Targets:" \
 		"  make fmt                       # gofmt -w ." \
-		"  make install-hooks             # install git pre-commit hook" \
+		"  make install-hooks             # install git pre-commit + commit-msg hooks" \
 		"  make test                      # go test ./..." \
 		"  make install                   # build and install with version from git" \
 		"  make tag VERSION=vX.Y.Z        # create annotated git tag (requires clean tree)" \
@@ -52,6 +52,10 @@ release: tag
 	git push origin "$(VERSION)"
 
 install-hooks:
-	@echo "Installing git pre-commit hook..."
-	@ln -sf ../../scripts/pre-commit.sh .git/hooks/pre-commit
-	@echo "Done. Hook installed at .git/hooks/pre-commit"
+	@common_dir=$$(git rev-parse --git-common-dir); \
+	repo_root=$$(cd "$$common_dir/.." && pwd -P); \
+	hooks_dir=$$(git rev-parse --git-path hooks); \
+	echo "Installing git hooks into $$hooks_dir..."; \
+	ln -sf "$$repo_root/scripts/pre-commit.sh" "$$hooks_dir/pre-commit"; \
+	ln -sf "$$repo_root/scripts/commit-msg.sh" "$$hooks_dir/commit-msg"; \
+	echo "Done. Hooks installed at $$hooks_dir/pre-commit and $$hooks_dir/commit-msg"

README.md

@@ -189,10 +189,32 @@ make install-dev
 # Format code
 make fmt
 
-# Install git pre-commit hook (gofmt, go vet, go build on staged files)
+# Install git hooks (pre-commit checks + commit subject normalization)
 make install-hooks
 ```
 
+## Commit Messages
+
+Install the hooks once per clone:
+
+```bash
+make install-hooks
+```
+
+Generate a canonical subject for the focused issue, or pass `--issue td-abc123`
+explicitly:
+
+```bash
+git commit \
+  -m "$(td commit-message 'normalize commit message workflow')" \
+  -m "Optional body text"
+```
+
+The `commit-msg` hook rewrites only the first line, preserves commit bodies and
+trailers, and leaves Git-generated merge/revert/autosquash subjects untouched.
+If no issue is focused, only typed `docs`, `test`, `chore`, and `ci` subjects
+such as `docs: Update changelog for v0.43.0` stay no-issue commits.
+
 ## Tests & Quality Checks
 
 ```bash
@@ -422,6 +444,7 @@ Analytics are stored locally and help identify workflow patterns. Disable with `
 | Reject                           | `td reject <id> --reason "..."`                  |
 | Link files                       | `td link <id> <files...>`                        |
 | Check file changes               | `td files <id>`                                  |
+| Normalize commit subject         | `td commit-message "summary"`                    |
 | Draft release notes              | `td release-notes --version v0.2.0`              |
 | Undo last action                 | `td undo`                                        |
 | New named session                | `td session --new "feature-work"`                |

cmd/commit_message.go

@@ -0,0 +1,188 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/marcus/td/internal/config"
+	"github.com/marcus/td/internal/db"
+	"github.com/marcus/td/internal/git"
+	"github.com/marcus/td/internal/models"
+	"github.com/marcus/td/internal/output"
+	"github.com/spf13/cobra"
+)
+
+var commitMessageCmd = &cobra.Command{
+	Use:     "commit-message [summary]",
+	Aliases: []string{"commit-msg"},
+	Short:   "Normalize a commit subject for the current td issue",
+	Long: `Normalize a commit subject to td's conventional format:
+  <type>: <summary> (td-<id>)
+
+The issue ID comes from --issue, a trailing (td-<id>) suffix already present in
+the subject, or the focused issue. When no issue is available, only typed
+docs/test/chore/ci subjects can stay no-issue commits. When
+--file is set, td rewrites only the first line of the commit message file in
+place and preserves the body/trailers. Git-generated merge, revert, and
+autosquash subjects are left unchanged.`,
+	Example: `  td commit-message "normalize commit hook docs"
+  td commit-message --issue td-a1b2 "normalize commit hook docs"
+  td commit-message --type docs "Update changelog for v0.43.0"
+  td commit-message --file .git/COMMIT_EDITMSG`,
+	GroupID: "system",
+	Args:    cobra.MaximumNArgs(1),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		baseDir := getBaseDir()
+
+		filePath, _ := cmd.Flags().GetString("file")
+		if filePath != "" && len(args) > 0 {
+			return fmt.Errorf("summary argument cannot be used with --file")
+		}
+		if filePath == "" && len(args) == 0 {
+			return fmt.Errorf(`summary required. Use: td commit-message [--issue <id>] "summary"`)
+		}
+
+		subject, err := commitMessageSubject(args, filePath)
+		if err != nil {
+			output.Error("%v", err)
+			return err
+		}
+
+		if git.ShouldSkipCommitMessageNormalization(subject) {
+			if filePath == "" {
+				_, _ = fmt.Fprintln(cmd.OutOrStdout(), strings.TrimSpace(subject))
+			}
+			return nil
+		}
+
+		issueID, issueType, err := resolveCommitMessageContext(baseDir, cmd, subject)
+		if err != nil {
+			output.Error("%v", err)
+			return err
+		}
+
+		explicitType, _ := cmd.Flags().GetString("type")
+		opts := git.CommitMessageOptions{
+			IssueID:   issueID,
+			IssueType: issueType,
+			Type:      git.CommitType(explicitType),
+		}
+
+		if filePath != "" {
+			if err := git.RewriteCommitMessageFile(filePath, opts); err != nil {
+				output.Error("%v", err)
+				return err
+			}
+			return nil
+		}
+
+		normalized, err := git.NormalizeCommitSubject(subject, opts)
+		if err != nil {
+			output.Error("%v", err)
+			return err
+		}
+
+		_, _ = fmt.Fprintln(cmd.OutOrStdout(), normalized)
+		return nil
+	},
+}
+
+func commitMessageSubject(args []string, filePath string) (string, error) {
+	if filePath == "" {
+		return args[0], nil
+	}
+
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		return "", err
+	}
+
+	message := string(data)
+	if idx := strings.Index(message, "\n"); idx >= 0 {
+		return strings.TrimSuffix(message[:idx], "\r"), nil
+	}
+
+	return message, nil
+}
+
+func resolveCommitMessageContext(baseDir string, cmd *cobra.Command, subject string) (string, models.Type, error) {
+	issueFlag, _ := cmd.Flags().GetString("issue")
+	issueID, err := normalizeCommitMessageIssueRef(baseDir, issueFlag)
+	if err != nil {
+		return "", "", err
+	}
+
+	if issueID == "" {
+		issueID, err = git.ExtractCommitIssueID(subject)
+		if err != nil {
+			return "", "", err
+		}
+	}
+
+	explicitType, _ := cmd.Flags().GetString("type")
+	if issueID == "" && strings.TrimSpace(explicitType) != "" {
+		commitType, err := git.NormalizeCommitType(explicitType)
+		if err != nil {
+			return "", "", err
+		}
+		if git.CommitTypeAllowsNoIssue(commitType) {
+			return "", "", nil
+		}
+	}
+
+	if issueID == "" {
+		focusedID, err := config.GetFocus(baseDir)
+		if err != nil {
+			return "", "", err
+		}
+		issueID, err = git.NormalizeCommitIssueID(focusedID)
+		if err != nil {
+			return "", "", err
+		}
+	}
+
+	if issueID == "" {
+		return "", "", nil
+	}
+
+	database, err := db.Open(baseDir)
+	if err != nil {
+		return "", "", err
+	}
+	defer database.Close()
+
+	issue, err := database.GetIssue(issueID)
+	if err != nil {
+		return "", "", err
+	}
+
+	return issueID, issue.Type, nil
+}
+
+func normalizeCommitMessageIssueRef(baseDir, raw string) (string, error) {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" {
+		return "", nil
+	}
+	if trimmed == "." {
+		focusedID, err := config.GetFocus(baseDir)
+		if err != nil {
+			return "", err
+		}
+		if strings.TrimSpace(focusedID) == "" {
+			return "", fmt.Errorf("no focused issue available for --issue .")
+		}
+		trimmed = focusedID
+	}
+
+	return git.NormalizeCommitIssueID(trimmed)
+}
+
+func init() {
+	rootCmd.AddCommand(commitMessageCmd)
+
+	commitMessageCmd.Flags().StringP("issue", "i", "", "Issue ID (default: subject suffix or focused issue)")
+	commitMessageCmd.Flags().StringP("type", "t", "", "Commit type override (feat, fix, docs, test, chore, ci)")
+	commitMessageCmd.Flags().StringP("file", "f", "", "Rewrite a commit message file in place")
+}