docs: add godoc on Manager and the builders

Author: ldez

pkg/lint/lintersdb/builder_linter.go

@@ -6,12 +6,16 @@ import (
 	"github.com/golangci/golangci-lint/pkg/lint/linter"
 )
 
+// LinterBuilder builds the "internal" linters based on the configuration.
 type LinterBuilder struct{}
 
+// NewLinterBuilder creates a new LinterBuilder.
 func NewLinterBuilder() *LinterBuilder {
 	return &LinterBuilder{}
 }
 
+// Build loads all the "internal" linters.
+// The configuration is use for the linter settings.
 func (b LinterBuilder) Build(cfg *config.Config) []*linter.Config {
 	if cfg == nil {
 		return nil

pkg/lint/lintersdb/builder_plugin.go

@@ -18,15 +18,17 @@ type AnalyzerPlugin interface {
 	GetAnalyzers() []*analysis.Analyzer
 }
 
+// PluginBuilder builds the custom linters (plugins) based on the configuration.
 type PluginBuilder struct {
 	log logutils.Log
 }
 
+// NewPluginBuilder creates new PluginBuilder.
 func NewPluginBuilder(log logutils.Log) *PluginBuilder {
 	return &PluginBuilder{log: log}
 }
 
-// Build loads private linters that are specified in the golangci-lint config file.
+// Build loads custom linters that are specified in the golangci-lint config file.
 func (b *PluginBuilder) Build(cfg *config.Config) []*linter.Config {
 	if cfg == nil || b.log == nil {
 		return nil

pkg/lint/lintersdb/manager.go

@@ -19,6 +19,8 @@ type Builder interface {
 	Build(cfg *config.Config) []*linter.Config
 }
 
+// Manager This a kind of database for all the linters (internals or plugins).
+// It provides methods to access to the linter sets.
 type Manager struct {
 	log    logutils.Log
 	debugf logutils.DebugFunc
@@ -30,6 +32,8 @@ type Manager struct {
 	nameToLCs map[string][]*linter.Config
 }
 
+// NewManager creates a new Manager.
+// This constructor will call the builders to build and store the linters.
 func NewManager(log logutils.Log, cfg *config.Config, builders ...Builder) (*Manager, error) {
 	m := &Manager{
 		log:       log,