Update golangci-lint to v2.12.2 with canonical config (#62)

Updates golangci-lint to v2.12.2 everywhere it is pinned and installs the canonical `.golangci.yml`, then remediates every finding the new linter/config surfaces so `make check` is green.

## Version bump

- `Dockerfile` lint stage: `golangci/golangci-lint:v2.11.3-alpine` -> `v2.12.2-alpine` (digest-pinned, date comment updated)
- `Makefile` `deps` target: `go install` moved from the old v1 module path at `@latest` to the pinned `github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.12.2`
- `.golangci.yml` replaced with the canonical config (v2 schema; settings under `linters.settings` so the thresholds actually apply; `default: all` with the standard six disables)
- `script/bootstrap` installs golangci-lint via the system package manager and carries no version pin, so it is unchanged
- CI (`.gitea/workflows/check.yml`) only runs `script/cibuild`, so it needed no change

## Lint remediation

The canonical config surfaced ~3,300 findings across 56k lines. All are fixed, behavior-preserving; incorporates and supersedes the per-package mechanical passes already merged to `main` (refs #61). Highlights:

- `err113`: dynamic errors replaced with package sentinels + `%w` wrapping; comparisons via `errors.Is`
- `goprintffuncname`: printf-style helpers renamed with an `f` suffix (`ui.Writer` message methods, `cli.ReportErrorf`, `database.Fatalf`) and all call sites updated
- `revive` stutter renames: `blob.Handler`, `blob.WithReader`, `blob.ChunkPosition`, `storage.URL`, `storage.Info`; missing doc comments added
- `contextcheck`/`noctx`: `context.Context` threaded through `blob.Packer` and the scanner call sites; context-aware `exec`/`sql` variants
- `funlen`/`cyclop`/`gocognit`/`dupl`: oversized and duplicated functions split into focused helpers (production and test code)
- tests: `t.Parallel()` added where safe (global logger init kept in the serial phase for `-race`), `t.TempDir()`/`t.Helper()` adopted, several suites converted to external test packages
- `gosec`: bounded integer conversions, `ReadHeaderTimeout` on the test HTTP server; remaining warnings suppressed per-site with justifications
- remaining `nolint` directives are rare, targeted, and each carries a reason (e.g. `nilnil` not-found contract in the repository layer, fx module globals, on-disk snake_case struct tags)
- removed the deprecated `log.LogOptions` alias (callers migrated to `log.Options`)

`make check` (tests with `-race`, lint, fmt-check) passes.

Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #62
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/config/config.go

@@ -1,3 +1,6 @@
+// Package config loads, validates, and provides the vaultik YAML
+// configuration, including snapshot definitions, encryption recipients,
+// and storage settings.
 package config
 
 import (
@@ -18,6 +21,38 @@ import (
 
 const appName = "vaultik"
 
+// Defaults and validation bounds for tunable settings.
+const (
+	defaultBlobSizeLimit    = Size(10 * 1024 * 1024 * 1024) // 10GB
+	defaultChunkSize        = Size(10 * 1024 * 1024)        // 10MB
+	defaultS3PartSize       = Size(5 * 1024 * 1024)         // 5MB
+	defaultCompressionLevel = 3
+	minChunkSize            = 1024 * 1024 // 1MB
+	minCompressionLevel     = 1
+	maxCompressionLevel     = 19
+)
+
+// Sentinel validation errors.
+var (
+	errNoConfigPath    = errors.New("config path not provided")
+	errNoAgeRecipients = errors.New(
+		"at least one age_recipient is required (generate with: age-keygen)")
+	errNoSnapshots = errors.New(
+		"at least one snapshot must be configured (see config.example.yml)")
+	errSnapshotNoPaths   = errors.New("snapshot must have at least one path")
+	errChunkSizeTooSmall = errors.New("chunk_size must be at least 1MB")
+	errBlobSizeTooSmall  = errors.New("blob_size_limit must be at least chunk_size")
+	errBadCompression    = errors.New("compression_level must be between 1 and 19")
+	errBadStorageScheme  = errors.New(
+		"storage_url must start with s3://, file://, or rclone://")
+	errStorageNotConfigured = errors.New(
+		"storage not configured; set storage_url or provide s3.endpoint + " +
+			"s3.bucket + credentials")
+	errS3BucketRequired = errors.New("s3.bucket is required (or set storage_url)")
+	errS3KeyIDRequired  = errors.New("s3.access_key_id is required")
+	errS3SecretRequired = errors.New("s3.secret_access_key is required")
+)
+
 // expandTilde expands ~ at the start of a path to the user's home directory.
 func expandTilde(path string) string {
 	if path == "~" {
@@ -90,12 +125,15 @@ func (c *Config) SnapshotNames() []string {
 // It defines all settings for backup operations, including source directories,
 // encryption recipients, storage configuration, and performance tuning parameters.
 // Configuration is typically loaded from a YAML file.
+//
+//nolint:tagliatelle // snake_case is the established config-file format
 type Config struct {
-	AgeRecipients    []string                  `yaml:"age_recipients"`
-	AgeSecretKey     string                    `yaml:"age_secret_key"`
-	BlobSizeLimit    Size                      `yaml:"blob_size_limit"`
-	ChunkSize        Size                      `yaml:"chunk_size"`
-	Exclude          []string                  `yaml:"exclude"` // Global excludes applied to all snapshots
+	AgeRecipients []string `yaml:"age_recipients"`
+	AgeSecretKey  string   `yaml:"age_secret_key"`
+	BlobSizeLimit Size     `yaml:"blob_size_limit"`
+	ChunkSize     Size     `yaml:"chunk_size"`
+	// Exclude holds global excludes applied to all snapshots.
+	Exclude          []string                  `yaml:"exclude"`
 	Hostname         string                    `yaml:"hostname"`
 	IndexPath        string                    `yaml:"index_path"`
 	S3               S3Config                  `yaml:"s3"`
@@ -107,13 +145,16 @@ type Config struct {
 	// Supported formats:
 	//   - s3://bucket/prefix?endpoint=host&region=us-east-1
 	//   - file:///path/to/backup
-	// For S3 URLs, credentials are still read from s3.access_key_id and s3.secret_access_key.
+	// For S3 URLs, credentials are still read from s3.access_key_id
+	// and s3.secret_access_key.
 	StorageURL string `yaml:"storage_url"`
 }
 
 // S3Config represents S3 storage configuration for backup storage.
 // It supports both AWS S3 and S3-compatible storage services.
 // All fields except UseSSL and PartSize are required.
+//
+//nolint:tagliatelle // snake_case is the established config-file format
 type S3Config struct {
 	Endpoint        string `yaml:"endpoint"`
 	Bucket          string `yaml:"bucket"`
@@ -125,17 +166,17 @@ type S3Config struct {
 	PartSize        Size   `yaml:"part_size"`
 }
 
-// ConfigPath wraps the config file path for fx dependency injection.
+// Path wraps the config file path for fx dependency injection.
 // This type allows the config file path to be injected as a distinct type
 // rather than a plain string, avoiding conflicts with other string dependencies.
-type ConfigPath string
+type Path string
 
 // New creates a new Config instance by loading from the specified path.
 // This function is used by the fx dependency injection framework.
 // Returns an error if the path is empty or if loading fails.
-func New(path ConfigPath) (*Config, error) {
+func New(path Path) (*Config, error) {
 	if path == "" {
-		return nil, errors.New("config path not provided")
+		return nil, errNoConfigPath
 	}
 
 	cfg, err := Load(string(path))
@@ -160,10 +201,10 @@ func Load(path string) (*Config, error) {
 
 	cfg := &Config{
 		// Set defaults
-		BlobSizeLimit:    Size(10 * 1024 * 1024 * 1024), // 10GB
-		ChunkSize:        Size(10 * 1024 * 1024),        // 10MB
+		BlobSizeLimit:    defaultBlobSizeLimit,
+		ChunkSize:        defaultChunkSize,
 		IndexPath:        filepath.Join(xdg.DataHome, appName, "index.sqlite"),
-		CompressionLevel: 3,
+		CompressionLevel: defaultCompressionLevel,
 	}
 
 	// Convert smartconfig data to YAML then unmarshal
@@ -218,12 +259,13 @@ func Load(path string) (*Config, error) {
 	}
 
 	if cfg.S3.PartSize == 0 {
-		cfg.S3.PartSize = Size(5 * 1024 * 1024) // 5MB
+		cfg.S3.PartSize = defaultS3PartSize
 	}
 
 	// Check config file permissions (warn if world or group readable)
-	info, err := os.Stat(path)
-	if err == nil {
+	//nolint:gosec // G703: config path is operator-supplied by design
+	info, statErr := os.Stat(path)
+	if statErr == nil {
 		mode := info.Mode().Perm()
 		if mode&0044 != 0 { // group or world readable
 			log.Warn("Config file has insecure permissions (contains S3 credentials)",
@@ -252,16 +294,16 @@ func Load(path string) (*Config, error) {
 // Returns an error describing the first validation failure encountered.
 func (c *Config) Validate() error {
 	if len(c.AgeRecipients) == 0 {
-		return errors.New("at least one age_recipient is required (generate with: age-keygen)")
+		return errNoAgeRecipients
 	}
 
 	if len(c.Snapshots) == 0 {
-		return errors.New("at least one snapshot must be configured (see config.example.yml)")
+		return errNoSnapshots
 	}
 
 	for name, snap := range c.Snapshots {
 		if len(snap.Paths) == 0 {
-			return fmt.Errorf("snapshot %q must have at least one path", name)
+			return fmt.Errorf("%w: %q", errSnapshotNoPaths, name)
 		}
 	}
 
@@ -271,16 +313,17 @@ func (c *Config) Validate() error {
 		return err
 	}
 
-	if c.ChunkSize.Int64() < 1024*1024 { // 1MB minimum
-		return errors.New("chunk_size must be at least 1MB")
+	if c.ChunkSize.Int64() < minChunkSize {
+		return errChunkSizeTooSmall
 	}
 
 	if c.BlobSizeLimit.Int64() < c.ChunkSize.Int64() {
-		return errors.New("blob_size_limit must be at least chunk_size")
+		return errBlobSizeTooSmall
 	}
 
-	if c.CompressionLevel < 1 || c.CompressionLevel > 19 {
-		return errors.New("compression_level must be between 1 and 19")
+	if c.CompressionLevel < minCompressionLevel ||
+		c.CompressionLevel > maxCompressionLevel {
+		return errBadCompression
 	}
 
 	return nil
@@ -292,53 +335,56 @@ func (c *Config) Validate() error {
 // If StorageURL is not set, legacy S3 configuration is required.
 func (c *Config) validateStorage() error {
 	if c.StorageURL != "" {
-		// URL-based configuration
-		if strings.HasPrefix(c.StorageURL, "file://") {
-			// File storage doesn't need S3 credentials
-			return nil
-		}
-
-		if strings.HasPrefix(c.StorageURL, "s3://") {
-			// S3 storage needs credentials
-			if c.S3.AccessKeyID == "" {
-				return errors.New("s3.access_key_id is required for s3:// URLs")
-			}
-
-			if c.S3.SecretAccessKey == "" {
-				return errors.New("s3.secret_access_key is required for s3:// URLs")
-			}
-
-			return nil
-		}
-
-		if strings.HasPrefix(c.StorageURL, "rclone://") {
-			// Rclone storage uses rclone's own config
-			return nil
-		}
-
-		return errors.New("storage_url must start with s3://, file://, or rclone://")
+		return c.validateStorageURL()
 	}
 
 	// Legacy S3 configuration
 	if c.S3.Endpoint == "" {
-		return errors.New("storage not configured; set storage_url or provide s3.endpoint + s3.bucket + credentials")
+		return errStorageNotConfigured
 	}
 
 	if c.S3.Bucket == "" {
-		return errors.New("s3.bucket is required (or set storage_url)")
+		return errS3BucketRequired
 	}
 
 	if c.S3.AccessKeyID == "" {
-		return errors.New("s3.access_key_id is required")
+		return errS3KeyIDRequired
 	}
 
 	if c.S3.SecretAccessKey == "" {
-		return errors.New("s3.secret_access_key is required")
+		return errS3SecretRequired
 	}
 
 	return nil
 }
 
+// validateStorageURL validates URL-based storage configuration. File and
+// rclone URLs need no credentials; S3 URLs require the legacy s3.*
+// credential fields.
+func (c *Config) validateStorageURL() error {
+	switch {
+	case strings.HasPrefix(c.StorageURL, "file://"):
+		// File storage doesn't need S3 credentials
+		return nil
+	case strings.HasPrefix(c.StorageURL, "rclone://"):
+		// Rclone storage uses rclone's own config
+		return nil
+	case strings.HasPrefix(c.StorageURL, "s3://"):
+		// S3 storage needs credentials
+		if c.S3.AccessKeyID == "" {
+			return fmt.Errorf("%w for s3:// URLs", errS3KeyIDRequired)
+		}
+
+		if c.S3.SecretAccessKey == "" {
+			return fmt.Errorf("%w for s3:// URLs", errS3SecretRequired)
+		}
+
+		return nil
+	default:
+		return errBadStorageScheme
+	}
+}
+
 // extractAgeSecretKey extracts the AGE-SECRET-KEY from the input using
 // the age library's parser, which handles comments and whitespace.
 func extractAgeSecretKey(input string) string {
@@ -357,6 +403,8 @@ func extractAgeSecretKey(input string) string {
 
 // Module exports the config module for fx dependency injection.
 // It provides the Config type to other modules in the application.
+//
+//nolint:gochecknoglobals // fx module definitions are package globals
 var Module = fx.Module("config",
 	fx.Provide(New),
 )