feat(commits): add Conventional Commits message normalizer + lint fixes

Makefile

@@ -75,10 +75,12 @@ help:
 	@echo "  check         - Run tests and lint"
 	@echo "  install       - Build and install to Go bin directory"
 	@echo "  calibrate-providers - Compare local Claude/Codex session usage for calibration"
-	@echo "  install-hooks  - Install git pre-commit hook"
+	@echo "  install-hooks  - Install git pre-commit and commit-msg hooks"
 	@echo "  help          - Show this help"
 
-# Install git pre-commit hook
+# Install git pre-commit and commit-msg hooks
 install-hooks:
 	@ln -sf ../../scripts/pre-commit.sh .git/hooks/pre-commit
 	@echo "✓ pre-commit hook installed (.git/hooks/pre-commit → scripts/pre-commit.sh)"
+	@ln -sf ../../scripts/commit-msg.sh .git/hooks/commit-msg
+	@echo "✓ commit-msg hook installed (.git/hooks/commit-msg → scripts/commit-msg.sh)"

cmd/nightshift/commands/commit.go

@@ -0,0 +1,101 @@
+package commands
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/marcus/nightshift/internal/commits"
+	"github.com/spf13/cobra"
+)
+
+var commitCmd = &cobra.Command{
+	Use:   "commit",
+	Short: "Conventional Commits helpers",
+	Long: `Tools for working with Conventional Commits messages.
+
+Use "commit normalize" to validate and reformat a commit message so it
+follows the project's rules (type prefix, lowercase type, subject length,
+and wrapped body).`,
+}
+
+var commitNormalizeCmd = &cobra.Command{
+	Use:   "normalize [MESSAGE]",
+	Short: "Normalize a commit message to Conventional Commits format",
+	Long: `Validate and rewrite a commit message into canonical Conventional
+Commits form.
+
+The message is read from a positional argument, from a file passed via
+--file (typically .git/COMMIT_EDITMSG by a commit-msg hook), or from stdin
+when no argument and no --file are given.
+
+  nightshift commit normalize "feat: add login"
+  nightshift commit normalize --file .git/COMMIT_EDITMSG
+  git log -1 --pretty=%B | nightshift commit normalize
+
+Use --check to only validate without rewriting: nothing is printed and the
+exit code is non-zero when the message is invalid or not already in canonical
+form.`,
+	Args:         cobra.MaximumNArgs(1),
+	SilenceUsage: true,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		check, _ := cmd.Flags().GetBool("check")
+		file, _ := cmd.Flags().GetString("file")
+
+		raw, err := readCommitMessage(args, file)
+		if err != nil {
+			return err
+		}
+
+		normalized, err := commits.Normalize(raw)
+		if err != nil {
+			return err
+		}
+
+		if check {
+			if !isCanonical(raw, normalized) {
+				return errors.New("message is not in canonical Conventional Commits form (run without --check to print the normalized message)")
+			}
+			return nil
+		}
+		if _, err := fmt.Fprintln(os.Stdout, normalized); err != nil {
+			return err
+		}
+		return nil
+	},
+}
+
+func init() {
+	commitNormalizeCmd.Flags().BoolP("check", "c", false, "Only validate; do not rewrite")
+	commitNormalizeCmd.Flags().StringP("file", "f", "", "Read the message from this file (use by the commit-msg hook)")
+	commitCmd.AddCommand(commitNormalizeCmd)
+	rootCmd.AddCommand(commitCmd)
+}
+
+// readCommitMessage resolves the message source in order: positional arg,
+// --file, then stdin.
+func readCommitMessage(args []string, file string) (string, error) {
+	if len(args) == 1 {
+		return args[0], nil
+	}
+	if file != "" {
+		b, err := os.ReadFile(file)
+		if err != nil {
+			return "", fmt.Errorf("read %s: %w", file, err)
+		}
+		return string(b), nil
+	}
+	b, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		return "", fmt.Errorf("read stdin: %w", err)
+	}
+	return string(b), nil
+}
+
+// isCanonical reports whether raw is already in normalized form, ignoring a
+// single trailing newline.
+func isCanonical(raw, normalized string) bool {
+	return strings.TrimSuffix(raw, "\n") == normalized
+}

cmd/nightshift/commands/commit_test.go

@@ -0,0 +1,61 @@
+package commands
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadCommitMessage(t *testing.T) {
+	t.Run("positional argument wins", func(t *testing.T) {
+		got, err := readCommitMessage([]string{"feat: add thing"}, "ignored-file")
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if got != "feat: add thing" {
+			t.Errorf("got %q, want %q", got, "feat: add thing")
+		}
+	})
+
+	t.Run("reads from file", func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "msg")
+		if err := os.WriteFile(path, []byte("fix: correct thing\n"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		got, err := readCommitMessage(nil, path)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if got != "fix: correct thing\n" {
+			t.Errorf("got %q, want %q", got, "fix: correct thing\n")
+		}
+	})
+
+	t.Run("missing file errors", func(t *testing.T) {
+		if _, err := readCommitMessage(nil, filepath.Join(t.TempDir(), "nope")); err == nil {
+			t.Error("expected an error for a missing file")
+		}
+	})
+}
+
+func TestIsCanonical(t *testing.T) {
+	tests := []struct {
+		name       string
+		raw        string
+		normalized string
+		want       bool
+	}{
+		{"exact match", "feat: add login", "feat: add login", true},
+		{"trailing newline ignored", "feat: add login\n", "feat: add login", true},
+		{"needs rewriting", "FEAT: add login", "feat: add login", false},
+		{"trailing blank lines", "feat: add login\n\n", "feat: add login", false},
+		{"extra whitespace", "  feat: add login  ", "feat: add login", false},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := isCanonical(tc.raw, tc.normalized); got != tc.want {
+				t.Errorf("isCanonical(%q, %q) = %v, want %v", tc.raw, tc.normalized, got, tc.want)
+			}
+		})
+	}
+}

cmd/nightshift/commands/config.go

@@ -370,7 +370,7 @@ func printStruct(v reflect.Value, indent int) {
 		case reflect.Struct:
 			fmt.Printf("%s%s:\n", prefix, tag)
 			printStruct(value, indent+1)
-		case reflect.Ptr:
+		case reflect.Pointer:
 			if !value.IsNil() {
 				if value.Elem().Kind() == reflect.Struct {
 					fmt.Printf("%s%s:\n", prefix, tag)
@@ -408,7 +408,7 @@ func printStruct(v reflect.Value, indent int) {
 
 func isZero(v reflect.Value) bool {
 	switch v.Kind() {
-	case reflect.Ptr, reflect.Interface:
+	case reflect.Pointer, reflect.Interface:
 		return v.IsNil()
 	case reflect.Slice, reflect.Map:
 		return v.Len() == 0

docs/commit-messages.md

@@ -0,0 +1,51 @@
+# Commit Messages
+
+Nightshift uses [Conventional Commits](https://www.conventionalcommits.org/)
+for all commit messages. This keeps the history readable and lets tooling
+derive changelogs automatically.
+
+## Format
+
+```
+<type>(<scope>): <subject>
+
+<body>
+```
+
+- **type** — one of `feat`, `fix`, `docs`, `style`, `refactor`, `test`,
+  `chore`, `perf`, `build`, `ci`.
+- **scope** — optional, e.g. `fix(api): ...`.
+- **breaking change** — append `!` after the type or scope, e.g. `feat(api)!:` —
+  a breaking change must also be called out in the body.
+- **subject** — lowercase, imperative mood, no trailing period, max 72 chars.
+- **body** — optional, wrapped at 72 columns, separated from the subject by a
+  blank line. Paragraph breaks are preserved and bullet-list items (`- ` /
+  `* `) stay on their own lines.
+
+## The `commit normalize` command
+
+Validate and reformat a message:
+
+```sh
+nightshift commit normalize "feat: add login screen"
+nightshift commit normalize --file .git/COMMIT_EDITMSG
+git log -1 --pretty=%B | nightshift commit normalize
+```
+
+Add `--check` to validate only: nothing is printed, and the command exits
+non-zero when a message cannot be normalized (missing/unknown type, capitalized
+or overlong subject) or is not already in canonical form.
+
+## commit-msg hook
+
+To enforce the rules locally, install the hook:
+
+```sh
+make install-hooks
+# or manually:
+ln -sf ../../scripts/commit-msg.sh .git/hooks/commit-msg
+```
+
+The hook normalizes your message file in place before the commit is created and
+rejects messages that cannot be fixed automatically. Bypass it with
+`git commit --no-verify`.