goheader: fix relative template path

go-header template-path setting is usually a relative filepath. As a
result, the linter only worked when golangci-lint was invoked from that
folder.

We detect if the template path is relative and prefix it with config
path.

go-header_bad.go test case was modified because old files are not
checked as seen here
https://github.com/denis-tingaikin/go-header/blob/v0.4.3/analyzer.go#L59-L63

Author: thejan2009

Diff for: pkg/golinters/goheader.go

@@ -2,6 +2,7 @@ package golinters
 
 import (
 	"go/token"
+	"path/filepath"
 	"sync"
 
 	goheader "github.com/denis-tingaikin/go-header"
@@ -15,16 +16,20 @@ import (
 
 const goHeaderName = "goheader"
 
-func NewGoHeader(settings *config.GoHeaderSettings) *goanalysis.Linter {
+func NewGoHeader(settings *config.GoHeaderSettings, cfg *config.Config) *goanalysis.Linter {
 	var mu sync.Mutex
 	var resIssues []goanalysis.Issue
 
 	conf := &goheader.Configuration{}
 	if settings != nil {
+		path := settings.TemplatePath
+		if path != "" && !filepath.IsAbs(path) {
+			path = filepath.Join(cfg.GetConfigDir(), path)
+		}
 		conf = &goheader.Configuration{
 			Values:       settings.Values,
 			Template:     settings.Template,
-			TemplatePath: settings.TemplatePath,
+			TemplatePath: path,
 		}
 	}
 

Diff for: pkg/lint/lintersdb/manager.go

@@ -511,7 +511,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithAutoFix().
 			WithURL("https://github.com/mvdan/gofumpt"),
 
-		linter.NewConfig(golinters.NewGoHeader(goheaderCfg)).
+		linter.NewConfig(golinters.NewGoHeader(goheaderCfg, m.cfg)).
 			WithSince("v1.28.0").
 			WithPresets(linter.PresetStyle).
 			WithURL("https://github.com/denis-tingaikin/go-header"),

Diff for: test/testdata/configs/go-header-template

@@ -0,0 +1 @@
+MY {{title}}

Diff for: test/testdata/configs/go-header.yml

@@ -1,6 +1,6 @@
 linters-settings:
   goheader:
-    template: MY {{title}}
+    template-path: go-header-template
     values:
       const:
         title: TITLE.

Diff for: test/testdata/go-header_bad.go

@@ -1,4 +1,4 @@
-/*MY TITLE!*/ // want `Expected:TITLE\., Actual: TITLE!`
+/*MY TITLE?*/ // want `Expected:TITLE\., Actual: TITLE?`
 
 //golangcitest:args -Egoheader
 //golangcitest:config_path testdata/configs/go-header.yml