Trim to 255 runes instead of bytes (#12150)

* Trim to 255 runes instead of bytes

Prevents invalid UTF-8 encoding for Description and Website. Refs #7905

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

Co-authored-by: techknowlogick <matti@mdranta.net>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>

models/repo.go

@@ -11,6 +11,7 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
+	"unicode/utf8"
 
 	// Needed for jpeg support
 	_ "image/jpeg"
@@ -1384,11 +1385,11 @@ func GetRepositoriesByForkID(forkID int64) ([]*Repository, error) {
 func updateRepository(e Engine, repo *Repository, visibilityChanged bool) (err error) {
 	repo.LowerName = strings.ToLower(repo.Name)
 
-	if len(repo.Description) > 255 {
-		repo.Description = repo.Description[:255]
+	if utf8.RuneCountInString(repo.Description) > 255 {
+		repo.Description = string([]rune(repo.Description)[:255])
 	}
-	if len(repo.Website) > 255 {
-		repo.Website = repo.Website[:255]
+	if utf8.RuneCountInString(repo.Website) > 255 {
+		repo.Website = string([]rune(repo.Website)[:255])
 	}
 
 	if _, err = e.ID(repo.ID).AllCols().Update(repo); err != nil {