Update golangci-lint to v2.12.2 with canonical config

- Replace .golangci.yml with the canonical strict config (all linters
  enabled except the standard disable list; lll 88, funlen 80/50,
  cyclop 15, dupl 100; test files now linted)
- Pin the Dockerfile lint stage to golangci/golangci-lint:v2.12.2 by
  tag and digest (Debian-based)
- Fix all ~1550 findings surfaced by the new config: line wrapping,
  wsl_v5/nlreturn blank lines, noinlineerr splits, err113 sentinel
  errors, perfsprint/modernize rewrites, goconst constants, thelper,
  testifylint, noctx CommandContext, testpackage conversions,
  t.Parallel() where safe, and complexity/dupl helper extraction
- Record the change and follow-up items in TODO.md

internal/cli/init.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"errors"
 	"fmt"
 	"log"
 	"log/slog"
@@ -8,6 +9,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"filippo.io/age"
 	"git.eeqj.de/sneak/secret/internal/secret"
 	"git.eeqj.de/sneak/secret/internal/vault"
 	"git.eeqj.de/sneak/secret/pkg/agehd"
@@ -16,13 +18,17 @@ import (
 	"github.com/tyler-smith/go-bip39"
 )
 
+// errPassphraseMismatch is returned when passphrase confirmation fails
+var errPassphraseMismatch = errors.New("passphrases do not match")
+
 // NewInitCmd creates the init command
 func NewInitCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:   "init",
 		Short: "Initialize the secrets manager",
-		Long:  `Create the necessary directory structure for storing secrets and generate encryption keys.`,
-		RunE:  RunInit,
+		Long: `Create the necessary directory structure for storing ` +
+			`secrets and generate encryption keys.`,
+		RunE: RunInit,
 	}
 }
 
@@ -36,6 +42,67 @@ func RunInit(cmd *cobra.Command, _ []string) error {
 	return cli.Init(cmd)
 }
 
+// promptMnemonic reads the mnemonic from the environment or interactively.
+// The returned cleanup function must be deferred by the caller.
+func promptMnemonic() (string, func(), error) {
+	if envMnemonic := os.Getenv(secret.EnvMnemonic); envMnemonic != "" {
+		secret.Debug("Using mnemonic from environment variable")
+
+		return envMnemonic, func() {}, nil
+	}
+
+	secret.Debug("Prompting user for mnemonic phrase")
+
+	// Read mnemonic securely without echo
+	mnemonicBuffer, err := secret.ReadPassphrase("Enter your BIP39 mnemonic phrase: ")
+	if err != nil {
+		secret.Debug("Failed to read mnemonic from stdin", "error", err)
+
+		return "", nil, fmt.Errorf("failed to read mnemonic: %w", err)
+	}
+
+	fmt.Fprintln(os.Stderr) // Add newline after hidden input
+
+	return mnemonicBuffer.String(), mnemonicBuffer.Destroy, nil
+}
+
+// setupDefaultVault creates the default vault and derives its long-term
+// identity from the mnemonic
+func (cli *Instance) setupDefaultVault(
+	stateDir, mnemonicStr string,
+) (*vault.Vault, *age.X25519Identity, error) {
+	// Create the default vault - it will handle key derivation internally
+	secret.Debug("Creating default vault")
+
+	vlt, err := vault.CreateVault(cli.fs, cli.stateDir, "default")
+	if err != nil {
+		secret.Debug("Failed to create default vault", "error", err)
+
+		return nil, nil, fmt.Errorf("failed to create default vault: %w", err)
+	}
+
+	// Get the vault metadata to retrieve the derivation index
+	vaultDir := filepath.Join(stateDir, "vaults.d", "default")
+
+	metadata, err := vault.LoadVaultMetadata(cli.fs, vaultDir)
+	if err != nil {
+		secret.Debug("Failed to load vault metadata", "error", err)
+
+		return nil, nil, fmt.Errorf("failed to load vault metadata: %w", err)
+	}
+
+	// Derive the long-term key using the same index that CreateVault used
+	ltIdentity, err := agehd.DeriveIdentity(mnemonicStr, metadata.DerivationIndex)
+	if err != nil {
+		secret.Debug("Failed to derive long-term key", "error", err)
+
+		return nil, nil, fmt.Errorf(
+			"failed to derive long-term key from mnemonic: %w", err)
+	}
+
+	return vlt, ltIdentity, nil
+}
+
 // Init initializes the secret manager
 func (cli *Instance) Init(cmd *cobra.Command) error {
 	secret.Debug("Starting secret manager initialization")
@@ -44,7 +111,8 @@ func (cli *Instance) Init(cmd *cobra.Command) error {
 	stateDir := cli.GetStateDir()
 	secret.DebugWith("Creating state directory", slog.String("path", stateDir))
 
-	if err := cli.fs.MkdirAll(stateDir, secret.DirPerms); err != nil {
+	err := cli.fs.MkdirAll(stateDir, secret.DirPerms)
+	if err != nil {
 		secret.Debug("Failed to create state directory", "error", err)
 
 		return fmt.Errorf("failed to create state directory: %w", err)
@@ -55,100 +123,55 @@ func (cli *Instance) Init(cmd *cobra.Command) error {
 	}
 
 	// Prompt for mnemonic
-	var mnemonicStr string
-
-	if envMnemonic := os.Getenv(secret.EnvMnemonic); envMnemonic != "" {
-		secret.Debug("Using mnemonic from environment variable")
-		mnemonicStr = envMnemonic
-	} else {
-		secret.Debug("Prompting user for mnemonic phrase")
-		// Read mnemonic securely without echo
-		mnemonicBuffer, err := secret.ReadPassphrase("Enter your BIP39 mnemonic phrase: ")
-		if err != nil {
-			secret.Debug("Failed to read mnemonic from stdin", "error", err)
-
-			return fmt.Errorf("failed to read mnemonic: %w", err)
-		}
-		defer mnemonicBuffer.Destroy()
-
-		mnemonicStr = mnemonicBuffer.String()
-		fmt.Fprintln(os.Stderr) // Add newline after hidden input
+	mnemonicStr, cleanupMnemonic, err := promptMnemonic()
+	if err != nil {
+		return err
 	}
+	defer cleanupMnemonic()
 
 	if mnemonicStr == "" {
 		secret.Debug("Empty mnemonic provided")
 
-		return fmt.Errorf("mnemonic cannot be empty")
+		return errMnemonicEmpty
 	}
 
 	// Validate the mnemonic using BIP39
-	secret.DebugWith("Validating BIP39 mnemonic", slog.Int("word_count", len(strings.Fields(mnemonicStr))))
+	secret.DebugWith("Validating BIP39 mnemonic",
+		slog.Int("word_count", len(strings.Fields(mnemonicStr))))
+
 	if !bip39.IsMnemonicValid(mnemonicStr) {
 		secret.Debug("Invalid BIP39 mnemonic provided")
 
-		return fmt.Errorf("invalid BIP39 mnemonic phrase\nRun 'secret generate mnemonic' to create a valid mnemonic")
+		return fmt.Errorf(
+			"%w\nRun 'secret generate mnemonic' to create a valid mnemonic",
+			errInvalidMnemonicPhrase)
 	}
 
 	// Set mnemonic in environment for CreateVault to use
-	originalMnemonic := os.Getenv(secret.EnvMnemonic)
-	_ = os.Setenv(secret.EnvMnemonic, mnemonicStr)
-	defer func() {
-		if originalMnemonic != "" {
-			_ = os.Setenv(secret.EnvMnemonic, originalMnemonic)
-		} else {
-			_ = os.Unsetenv(secret.EnvMnemonic)
-		}
-	}()
+	restoreMnemonicEnv := setMnemonicEnv(mnemonicStr)
+	defer restoreMnemonicEnv()
 
-	// Create the default vault - it will handle key derivation internally
-	secret.Debug("Creating default vault")
-	vlt, err := vault.CreateVault(cli.fs, cli.stateDir, "default")
+	// Create the default vault and derive its long-term key
+	vlt, ltIdentity, err := cli.setupDefaultVault(stateDir, mnemonicStr)
 	if err != nil {
-		secret.Debug("Failed to create default vault", "error", err)
-
-		return fmt.Errorf("failed to create default vault: %w", err)
+		return err
 	}
 
-	// Get the vault metadata to retrieve the derivation index
-	vaultDir := filepath.Join(stateDir, "vaults.d", "default")
-	metadata, err := vault.LoadVaultMetadata(cli.fs, vaultDir)
-	if err != nil {
-		secret.Debug("Failed to load vault metadata", "error", err)
-
-		return fmt.Errorf("failed to load vault metadata: %w", err)
-	}
-
-	// Derive the long-term key using the same index that CreateVault used
-	ltIdentity, err := agehd.DeriveIdentity(mnemonicStr, metadata.DerivationIndex)
-	if err != nil {
-		secret.Debug("Failed to derive long-term key", "error", err)
-
-		return fmt.Errorf("failed to derive long-term key from mnemonic: %w", err)
-	}
 	ltPubKey := ltIdentity.Recipient().String()
 
 	// Unlock the vault with the derived long-term key
 	vlt.Unlock(ltIdentity)
 
 	// Prompt for passphrase for unlocker
-	var passphraseBuffer *memguard.LockedBuffer
-	if envPassphrase := os.Getenv(secret.EnvUnlockPassphrase); envPassphrase != "" {
-		secret.Debug("Using unlock passphrase from environment variable")
-		passphraseBuffer = memguard.NewBufferFromBytes([]byte(envPassphrase))
-	} else {
-		secret.Debug("Prompting user for unlock passphrase")
-		// Use secure passphrase input with confirmation
-		passphraseBuffer, err = readSecurePassphrase("Enter passphrase for unlocker: ")
-		if err != nil {
-			secret.Debug("Failed to read unlock passphrase", "error", err)
-
-			return fmt.Errorf("failed to read passphrase: %w", err)
-		}
+	passphraseBuffer, err := resolvePassphrase()
+	if err != nil {
+		return err
 	}
 	defer passphraseBuffer.Destroy()
 
 	// Create passphrase-protected unlocker
 	secret.Debug("Creating passphrase-protected unlocker")
+
 	passphraseUnlocker, err := vlt.CreatePassphraseUnlocker(passphraseBuffer)
 	if err != nil {
 		secret.Debug("Failed to create unlocker", "error", err)
@@ -194,7 +217,7 @@ func readSecurePassphrase(prompt string) (*memguard.LockedBuffer, error) {
 		passphraseBuffer1.Destroy()
 		passphraseBuffer2.Destroy()
 
-		return nil, fmt.Errorf("passphrases do not match")
+		return nil, errPassphraseMismatch
 	}
 
 	// Clean up the second buffer, we'll return the first