chore: add modernizer linter (#11936)

- Go has a suite of small linters that helps with modernizing Go code by using newer functions and catching small mistakes, https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/modernize.
- Enable this linter in golangci-lint.
- There's also [`go fix`](https://go.dev/blog/gofix), which is not yet released as a linter in golangci-lint: https://github.com/golangci/golangci-lint/pull/6385

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11936
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

modules/validation/binding.go

@@ -266,17 +266,17 @@ func addEmailBindingRules() {
 }
 
 func portOnly(hostport string) string {
-	colon := strings.IndexByte(hostport, ':')
-	if colon == -1 {
+	_, after, ok := strings.Cut(hostport, ":")
+	if !ok {
 		return ""
 	}
-	if i := strings.Index(hostport, "]:"); i != -1 {
-		return hostport[i+len("]:"):]
+	if _, after, ok := strings.Cut(hostport, "]:"); ok {
+		return after
 	}
 	if strings.Contains(hostport, "]") {
 		return ""
 	}
-	return hostport[colon+len(":"):]
+	return after
 }
 
 func validPort(p string) bool {

modules/validation/helpers.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"net/url"
 	"regexp"
+	"slices"
 	"strings"
 
 	"forgejo.org/modules/setting"
@@ -40,12 +41,7 @@ func IsValidSiteURL(uri string) bool {
 		return false
 	}
 
-	for _, scheme := range setting.Service.ValidSiteURLSchemes {
-		if scheme == u.Scheme {
-			return true
-		}
-	}
-	return false
+	return slices.Contains(setting.Service.ValidSiteURLSchemes, u.Scheme)
 }
 
 // IsAPIURL checks if URL is current Gitea instance API URL

modules/validation/validatable.go

@@ -6,6 +6,7 @@ package validation
 import (
 	"fmt"
 	"reflect"
+	"slices"
 	"strings"
 	"unicode/utf8"
 
@@ -87,10 +88,8 @@ func ValidateMaxLen(value string, maxLen int, name string) []string {
 }
 
 func ValidateOneOf(value any, allowed []any, name string) []string {
-	for _, allowedElem := range allowed {
-		if value == allowedElem {
-			return []string{}
-		}
+	if slices.Contains(allowed, value) {
+		return []string{}
 	}
 	return []string{fmt.Sprintf("Field %s contains the value %v, which is not in allowed subset %v", name, value, allowed)}
 }