chore: misc go 1.27 tweaks (#39069)

Follow-up to https://github.com/go-gitea/gitea/pull/39068, which
disabled `modernize` entirely.

- re-enable `modernize`, with only the new `embedlit` rule disabled. It
flattens embedded struct literals across ~145 files, and orphans imports
in 6 of them that the fixer does not remove
- apply the rest of the suite: `errors.AsType`, `reflect.TypeAssert`,
`strings.Cut`, and dropping the legacy import comment
- use the new stdlib `uuid` package, `github.com/google/uuid` becomes
indirect
- use `strings.CutLast` in place of manual `LastIndex` slicing in label
scopes, email domains and the diff tree list
- take the header lint skip dirs from the `go.mod` `ignore` directive
and skip dot-directories, instead of hardcoding the list

Assisted-by: Claude Code:claude-opus-5

modules/avatar/federated.go

@@ -16,11 +16,11 @@ import (
 
 // LookupFederatedHost returns the avatar host from the email domain's SRV record. https://wiki.libravatar.org/api/
 func LookupFederatedHost(ctx context.Context, email string, secure bool) string {
-	at := strings.LastIndexByte(email, '@')
-	if at < 0 {
+	_, domain, found := strings.CutLast(email, "@")
+	if !found {
 		return ""
 	}
-	domain := strings.ToLower(email[at+1:])
+	domain = strings.ToLower(domain)
 
 	service, defaultPort := "avatars", uint16(80)
 	if secure {

modules/git/commit.go

@@ -114,8 +114,7 @@ func (c *Commit) HasPreviousCommit(ctx context.Context, gitRepo *Repository, obj
 	if err == nil {
 		return true, nil
 	}
-	var exitError *exec.ExitError
-	if errors.As(err, &exitError) {
+	if exitError, ok := errors.AsType[*exec.ExitError](err); ok {
 		if exitError.ProcessState.ExitCode() == 1 && len(exitError.Stderr) == 0 {
 			return false, nil
 		}

modules/log/logger_impl.go

@@ -184,7 +184,7 @@ func asLogStringer(v any) LogStringer {
 		// in case the receiver is a pointer, but the value is a struct
 		vp := reflect.New(a.Type())
 		vp.Elem().Set(a)
-		if s, ok := vp.Interface().(LogStringer); ok {
+		if s, ok := reflect.TypeAssert[LogStringer](vp); ok {
 			return s
 		}
 	}

modules/setting/actions.go

@@ -102,7 +102,7 @@ func loadActionsFrom(rootCfg ConfigProvider) error {
 	}
 
 	if urls := string(Actions.DefaultActionsURL); urls != defaultActionsURLGitHub && urls != defaultActionsURLSelf {
-		url := strings.Split(urls, ",")[0]
+		url, _, _ := strings.Cut(urls, ",")
 		if strings.HasPrefix(url, "https://") || strings.HasPrefix(url, "http://") {
 			log.Error("[actions] DEFAULT_ACTIONS_URL does not support %q as custom URL any longer, fallback to %q",
 				urls,

modules/structs/attachment.go

@@ -1,7 +1,7 @@
 // Copyright 2017 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT
 
-package structs // import "gitea.dev/modules/structs"
+package structs
 
 import (
 	"time"

modules/util/error.go

@@ -99,8 +99,7 @@ func ErrorWrapTranslatable(err error, trKey string, trArgs ...any) ErrorTranslat
 }
 
 func ErrorAsTranslatable(err error) ErrorTranslatable {
-	var e *errorTranslatableWrapper
-	if errors.As(err, &e) {
+	if e, ok := errors.AsType[*errorTranslatableWrapper](err); ok {
 		return e
 	}
 	return nil

modules/validation/helpers.go

@@ -64,12 +64,12 @@ func IsEmailDomainListed(globs []glob.Glob, email string) bool {
 		return false
 	}
 
-	n := strings.LastIndex(email, "@")
-	if n <= 0 {
+	localPart, domain, found := strings.CutLast(email, "@")
+	if !found || localPart == "" {
 		return false
 	}
 
-	domain := strings.ToLower(email[n+1:])
+	domain = strings.ToLower(domain)
 
 	for _, g := range globs {
 		if g.Match(domain) {

modules/web/handler.go

@@ -66,7 +66,7 @@ var (
 func preCheckHandler(fn reflect.Value, argsIn []reflect.Value) {
 	hasStatusProvider := false
 	for _, argIn := range argsIn {
-		if _, hasStatusProvider = argIn.Interface().(types.ResponseStatusProvider); hasStatusProvider {
+		if _, hasStatusProvider = reflect.TypeAssert[types.ResponseStatusProvider](argIn); hasStatusProvider {
 			break
 		}
 	}
@@ -119,7 +119,7 @@ func handleResponse(fn reflect.Value, ret []reflect.Value) {
 
 func hasResponseBeenWritten(argsIn []reflect.Value) bool {
 	for _, argIn := range argsIn {
-		if statusProvider, ok := argIn.Interface().(types.ResponseStatusProvider); ok {
+		if statusProvider, ok := reflect.TypeAssert[types.ResponseStatusProvider](argIn); ok {
 			if statusProvider.WrittenStatus() != 0 {
 				return true
 			}