From e5e1b35ca8248adce3774c1894040569ff840ce4 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 18:19:02 +0100
Subject: [PATCH 01/22] Unexport SendUserMail

---
 services/mailer/mail.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 7d6214c742a5c..1668ac1cd00bf 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -57,8 +57,8 @@ func SendTestMail(email string) error {
 	return gomail.Send(Sender, NewMessage([]string{email}, "Gitea Test Email!", "Gitea Test Email!").ToMessage())
 }
 
-// SendUserMail sends a mail to the user
-func SendUserMail(language string, u *models.User, tpl base.TplName, code, subject, info string) {
+// sendUserMail sends a mail to the user
+func sendUserMail(language string, u *models.User, tpl base.TplName, code, subject, info string) {
 	data := map[string]interface{}{
 		"DisplayName":       u.DisplayName(),
 		"ActiveCodeLives":   timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, language),
@@ -87,12 +87,12 @@ type Locale interface {
 
 // SendActivateAccountMail sends an activation mail to the user (new user registration)
 func SendActivateAccountMail(locale Locale, u *models.User) {
-	SendUserMail(locale.Language(), u, mailAuthActivate, u.GenerateActivateCode(), locale.Tr("mail.activate_account"), "activate account")
+	sendUserMail(locale.Language(), u, mailAuthActivate, u.GenerateActivateCode(), locale.Tr("mail.activate_account"), "activate account")
 }
 
 // SendResetPasswordMail sends a password reset mail to the user
 func SendResetPasswordMail(locale Locale, u *models.User) {
-	SendUserMail(locale.Language(), u, mailAuthResetPassword, u.GenerateActivateCode(), locale.Tr("mail.reset_password"), "recover account")
+	sendUserMail(locale.Language(), u, mailAuthResetPassword, u.GenerateActivateCode(), locale.Tr("mail.reset_password"), "recover account")
 }
 
 // SendActivateEmailMail sends confirmation email to confirm new email address

From db5059eb60d914ae073a369076e3f6bca3fd1b5a Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 18:23:02 +0100
Subject: [PATCH 02/22] Instead of "[]*models.User" or "[]string" lists infent
 "[]*MailRecipient" for mailer

---
 services/mailer/mail.go | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 1668ac1cd00bf..a187810288889 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -46,6 +46,28 @@ var (
 	subjectRemoveSpaces = regexp.MustCompile(`[\s]+`)
 )
 
+type MailRecipient struct {
+	Mail     string
+	Language string
+}
+
+// Convert User into MailRecipient
+func UserToMailRecipient(user *models.User) *MailRecipient {
+	return &MailRecipient{
+		Mail:     user.Email,
+		Language: user.Language,
+	}
+}
+
+// Convert list of User into list of MailRecipient
+func UsersToMailRecipients(users []*models.User) []*MailRecipient {
+	recipients := make([]*MailRecipient, 0, len(users))
+	for i := range users {
+		recipients[i] = UserToMailRecipient(users[i])
+	}
+	return recipients
+}
+
 // InitMailRender initializes the mail renderer
 func InitMailRender(subjectTpl *texttmpl.Template, bodyTpl *template.Template) {
 	subjectTemplates = subjectTpl

From bb8d32215b606599383692420321343cf5d43695 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 20:10:19 +0100
Subject: [PATCH 03/22] adopt

---
 models/user.go                     |  5 ----
 modules/notification/mail/mail.go  | 12 +++++-----
 modules/translation/translation.go |  4 ++++
 routers/admin/users.go             |  2 +-
 routers/api/v1/admin/user.go       |  2 +-
 routers/repo/setting.go            |  2 +-
 routers/user/auth.go               |  8 +++----
 routers/user/auth_openid.go        |  2 +-
 routers/user/setting/account.go    |  6 ++---
 services/mailer/mail.go            | 37 ++++++++++++++++++------------
 services/mailer/mail_comment.go    | 17 +++++---------
 services/mailer/mail_issue.go      |  7 +-----
 services/mailer/mail_test.go       | 11 ++++++---
 13 files changed, 58 insertions(+), 57 deletions(-)

diff --git a/models/user.go b/models/user.go
index 098f6af2b374a..aacf2957e3d4b 100644
--- a/models/user.go
+++ b/models/user.go
@@ -331,11 +331,6 @@ func (u *User) GenerateEmailActivateCode(email string) string {
 	return code
 }
 
-// GenerateActivateCode generates an activate code based on user information.
-func (u *User) GenerateActivateCode() string {
-	return u.GenerateEmailActivateCode(u.Email)
-}
-
 // GetFollowers returns range of user's followers.
 func (u *User) GetFollowers(listOptions ListOptions) ([]*User, error) {
 	sess := x.
diff --git a/modules/notification/mail/mail.go b/modules/notification/mail/mail.go
index f7192f5a52eff..24d112d808803 100644
--- a/modules/notification/mail/mail.go
+++ b/modules/notification/mail/mail.go
@@ -41,7 +41,7 @@ func (m *mailNotifier) NotifyCreateIssueComment(doer *models.User, repo *models.
 		act = 0
 	}
 
-	if err := mailer.MailParticipantsComment(comment, act, issue, mentions); err != nil {
+	if err := mailer.MailParticipantsComment(comment, act, issue, mailer.UsersToMailRecipients(mentions)); err != nil {
 		log.Error("MailParticipantsComment: %v", err)
 	}
 }
@@ -89,13 +89,13 @@ func (m *mailNotifier) NotifyPullRequestReview(pr *models.PullRequest, r *models
 	} else if comment.Type == models.CommentTypeComment {
 		act = models.ActionCommentPull
 	}
-	if err := mailer.MailParticipantsComment(comment, act, pr.Issue, mentions); err != nil {
+	if err := mailer.MailParticipantsComment(comment, act, pr.Issue, mailer.UsersToMailRecipients(mentions)); err != nil {
 		log.Error("MailParticipantsComment: %v", err)
 	}
 }
 
 func (m *mailNotifier) NotifyPullRequestCodeComment(pr *models.PullRequest, comment *models.Comment, mentions []*models.User) {
-	if err := mailer.MailMentionsComment(pr, comment, mentions); err != nil {
+	if err := mailer.MailMentionsComment(pr, comment, mailer.UsersToMailRecipients(mentions)); err != nil {
 		log.Error("MailMentionsComment: %v", err)
 	}
 }
@@ -104,14 +104,14 @@ func (m *mailNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *model
 	// mail only sent to added assignees and not self-assignee
 	if !removed && doer.ID != assignee.ID && assignee.EmailNotifications() == models.EmailNotificationsEnabled {
 		ct := fmt.Sprintf("Assigned #%d.", issue.Index)
-		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []string{assignee.Email})
+		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*mailer.MailRecipient{mailer.UserToMailRecipient(assignee)})
 	}
 }
 
 func (m *mailNotifier) NotifyPullReviewRequest(doer *models.User, issue *models.Issue, reviewer *models.User, isRequest bool, comment *models.Comment) {
 	if isRequest && doer.ID != reviewer.ID && reviewer.EmailNotifications() == models.EmailNotificationsEnabled {
 		ct := fmt.Sprintf("Requested to review %s.", issue.HTMLURL())
-		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []string{reviewer.Email})
+		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*mailer.MailRecipient{mailer.UserToMailRecipient(reviewer)})
 	}
 }
 
@@ -153,7 +153,7 @@ func (m *mailNotifier) NotifyPullRequestPushCommits(doer *models.User, pr *model
 }
 
 func (m *mailNotifier) NotifyPullRevieweDismiss(doer *models.User, review *models.Review, comment *models.Comment) {
-	if err := mailer.MailParticipantsComment(comment, models.ActionPullReviewDismissed, review.Issue, []*models.User{}); err != nil {
+	if err := mailer.MailParticipantsComment(comment, models.ActionPullReviewDismissed, review.Issue, nil); err != nil {
 		log.Error("MailParticipantsComment: %v", err)
 	}
 }
diff --git a/modules/translation/translation.go b/modules/translation/translation.go
index b7276e53c0149..f9ab035e1f7c8 100644
--- a/modules/translation/translation.go
+++ b/modules/translation/translation.go
@@ -90,6 +90,10 @@ type locale struct {
 
 // NewLocale return a locale
 func NewLocale(lang string) Locale {
+	if len(lang) != 5 {
+		// TODO: default language
+		lang = allLangs[0].Lang
+	}
 	return &locale{
 		Lang: lang,
 	}
diff --git a/routers/admin/users.go b/routers/admin/users.go
index 2d40a883af3db..e3f569203075b 100644
--- a/routers/admin/users.go
+++ b/routers/admin/users.go
@@ -154,7 +154,7 @@ func NewUserPost(ctx *context.Context) {
 
 	// Send email notification.
 	if form.SendNotify {
-		mailer.SendRegisterNotifyMail(ctx.Locale, u)
+		mailer.SendRegisterNotifyMail(u)
 	}
 
 	ctx.Flash.Success(ctx.Tr("admin.users.new_success", u.Name))
diff --git a/routers/api/v1/admin/user.go b/routers/api/v1/admin/user.go
index 116c622048d65..fceb038f5bd8c 100644
--- a/routers/api/v1/admin/user.go
+++ b/routers/api/v1/admin/user.go
@@ -114,7 +114,7 @@ func CreateUser(ctx *context.APIContext) {
 
 	// Send email notification.
 	if form.SendNotify {
-		mailer.SendRegisterNotifyMail(ctx.Locale, u)
+		mailer.SendRegisterNotifyMail(u)
 	}
 	ctx.JSON(http.StatusCreated, convert.ToUser(u, ctx.IsSigned, ctx.User.IsAdmin))
 }
diff --git a/routers/repo/setting.go b/routers/repo/setting.go
index dc14b69b3b0b0..805c90004d013 100644
--- a/routers/repo/setting.go
+++ b/routers/repo/setting.go
@@ -684,7 +684,7 @@ func CollaborationPost(ctx *context.Context) {
 	}
 
 	if setting.Service.EnableNotifyMail {
-		mailer.SendCollaboratorMail(u, ctx.User, ctx.Repo.Repository)
+		mailer.SendCollaboratorMail(mailer.UserToMailRecipient(u), ctx.User, ctx.Repo.Repository)
 	}
 
 	ctx.Flash.Success(ctx.Tr("repo.settings.add_collaborator_success"))
diff --git a/routers/user/auth.go b/routers/user/auth.go
index 37181c68e7a24..6853633dd7216 100644
--- a/routers/user/auth.go
+++ b/routers/user/auth.go
@@ -1028,7 +1028,7 @@ func LinkAccountPostRegister(ctx *context.Context) {
 
 	// Send confirmation email
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale, u)
+		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
@@ -1213,7 +1213,7 @@ func SignUpPost(ctx *context.Context) {
 
 	// Send confirmation email, no need for social account.
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale, u)
+		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
@@ -1247,7 +1247,7 @@ func Activate(ctx *context.Context) {
 				ctx.Data["ResendLimited"] = true
 			} else {
 				ctx.Data["ActiveCodeLives"] = timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, ctx.Locale.Language())
-				mailer.SendActivateAccountMail(ctx.Locale, ctx.User)
+				mailer.SendActivateAccountMail(ctx.Locale.Language(), ctx.User)
 
 				if err := ctx.Cache.Put("MailResendLimit_"+ctx.User.LowerName, ctx.User.LowerName, 180); err != nil {
 					log.Error("Set cache(MailResendLimit) fail: %v", err)
@@ -1397,7 +1397,7 @@ func ForgotPasswdPost(ctx *context.Context) {
 		return
 	}
 
-	mailer.SendResetPasswordMail(ctx.Locale, u)
+	mailer.SendResetPasswordMail(u.Language, u)
 
 	if err = ctx.Cache.Put("MailResendLimit_"+u.LowerName, u.LowerName, 180); err != nil {
 		log.Error("Set cache(MailResendLimit) fail: %v", err)
diff --git a/routers/user/auth_openid.go b/routers/user/auth_openid.go
index 967e8aad2d436..3064a354f6149 100644
--- a/routers/user/auth_openid.go
+++ b/routers/user/auth_openid.go
@@ -467,7 +467,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 
 	// Send confirmation email, no need for social account.
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale, u)
+		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
diff --git a/routers/user/setting/account.go b/routers/user/setting/account.go
index 4900bba14ac0c..eb33c45200c18 100644
--- a/routers/user/setting/account.go
+++ b/routers/user/setting/account.go
@@ -112,7 +112,7 @@ func EmailPost(ctx *context.Context) {
 				ctx.Redirect(setting.AppSubURL + "/user/settings/account")
 				return
 			}
-			mailer.SendActivateAccountMail(ctx.Locale, ctx.User)
+			mailer.SendActivateAccountMail(ctx.Locale.Language(), ctx.User)
 			address = ctx.User.Email
 		} else {
 			id := ctx.QueryInt64("id")
@@ -132,7 +132,7 @@ func EmailPost(ctx *context.Context) {
 				ctx.Redirect(setting.AppSubURL + "/user/settings/account")
 				return
 			}
-			mailer.SendActivateEmailMail(ctx.Locale, ctx.User, email)
+			mailer.SendActivateEmailMail(ctx.User, email)
 			address = email.Email
 		}
 
@@ -194,7 +194,7 @@ func EmailPost(ctx *context.Context) {
 
 	// Send confirmation email
 	if setting.Service.RegisterEmailConfirm {
-		mailer.SendActivateEmailMail(ctx.Locale, ctx.User, email)
+		mailer.SendActivateEmailMail(ctx.User, email)
 		if err := ctx.Cache.Put("MailResendLimit_"+ctx.User.LowerName, ctx.User.LowerName, 180); err != nil {
 			log.Error("Set cache(MailResendLimit) fail: %v", err)
 		}
diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index a187810288889..e63857d8ae8ff 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -22,6 +22,7 @@ import (
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
+	"code.gitea.io/gitea/modules/translation"
 
 	"gopkg.in/gomail.v2"
 )
@@ -47,6 +48,7 @@ var (
 )
 
 type MailRecipient struct {
+	userID   int64
 	Mail     string
 	Language string
 }
@@ -54,6 +56,7 @@ type MailRecipient struct {
 // Convert User into MailRecipient
 func UserToMailRecipient(user *models.User) *MailRecipient {
 	return &MailRecipient{
+		userID:   user.ID,
 		Mail:     user.Email,
 		Language: user.Language,
 	}
@@ -61,7 +64,7 @@ func UserToMailRecipient(user *models.User) *MailRecipient {
 
 // Convert list of User into list of MailRecipient
 func UsersToMailRecipients(users []*models.User) []*MailRecipient {
-	recipients := make([]*MailRecipient, 0, len(users))
+	recipients := make([]*MailRecipient, len(users))
 	for i := range users {
 		recipients[i] = UserToMailRecipient(users[i])
 	}
@@ -108,17 +111,20 @@ type Locale interface {
 }
 
 // SendActivateAccountMail sends an activation mail to the user (new user registration)
-func SendActivateAccountMail(locale Locale, u *models.User) {
-	sendUserMail(locale.Language(), u, mailAuthActivate, u.GenerateActivateCode(), locale.Tr("mail.activate_account"), "activate account")
+func SendActivateAccountMail(lang string, u *models.User) {
+	locale := translation.NewLocale(lang)
+	sendUserMail(lang, u, mailAuthActivate, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.activate_account"), "activate account")
 }
 
 // SendResetPasswordMail sends a password reset mail to the user
-func SendResetPasswordMail(locale Locale, u *models.User) {
-	sendUserMail(locale.Language(), u, mailAuthResetPassword, u.GenerateActivateCode(), locale.Tr("mail.reset_password"), "recover account")
+func SendResetPasswordMail(lang string, u *models.User) {
+	locale := translation.NewLocale(lang)
+	sendUserMail(lang, u, mailAuthResetPassword, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.reset_password"), "recover account")
 }
 
 // SendActivateEmailMail sends confirmation email to confirm new email address
-func SendActivateEmailMail(locale Locale, u *models.User, email *models.EmailAddress) {
+func SendActivateEmailMail(u *models.User, email *models.EmailAddress) {
+	locale := translation.NewLocale(u.Language)
 	data := map[string]interface{}{
 		"DisplayName":     u.DisplayName(),
 		"ActiveCodeLives": timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, locale.Language()),
@@ -140,7 +146,8 @@ func SendActivateEmailMail(locale Locale, u *models.User, email *models.EmailAdd
 }
 
 // SendRegisterNotifyMail triggers a notify e-mail by admin created a account.
-func SendRegisterNotifyMail(locale Locale, u *models.User) {
+func SendRegisterNotifyMail(u *models.User) {
+	locale := translation.NewLocale(u.Language)
 	if setting.MailService == nil {
 		log.Warn("SendRegisterNotifyMail is being invoked but mail service hasn't been initialized")
 		return
@@ -165,7 +172,7 @@ func SendRegisterNotifyMail(locale Locale, u *models.User) {
 }
 
 // SendCollaboratorMail sends mail notification to new collaborator.
-func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
+func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *models.Repository) {
 	repoName := repo.FullName()
 	subject := fmt.Sprintf("%s added you to %s", doer.DisplayName(), repoName)
 
@@ -182,13 +189,13 @@ func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 		return
 	}
 
-	msg := NewMessage([]string{u.Email}, subject, content.String())
-	msg.Info = fmt.Sprintf("UID: %d, add collaborator", u.ID)
+	msg := NewMessage([]string{recipient.Mail}, subject, content.String())
+	msg.Info = fmt.Sprintf("UID: %d, add collaborator", recipient.userID)
 
 	SendAsync(msg)
 }
 
-func composeIssueCommentMessages(ctx *mailCommentContext, tos []string, fromMention bool, info string) []*Message {
+func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailRecipient, fromMention bool, info string) []*Message {
 
 	var (
 		subject string
@@ -270,9 +277,9 @@ func composeIssueCommentMessages(ctx *mailCommentContext, tos []string, fromMent
 	}
 
 	// Make sure to compose independent messages to avoid leaking user emails
-	msgs := make([]*Message, 0, len(tos))
-	for _, to := range tos {
-		msg := NewMessageFrom([]string{to}, ctx.Doer.DisplayName(), setting.MailService.FromEmail, subject, mailBody.String())
+	msgs := make([]*Message, 0, len(recipients))
+	for _, to := range recipients {
+		msg := NewMessageFrom([]string{to.Mail}, ctx.Doer.DisplayName(), setting.MailService.FromEmail, subject, mailBody.String())
 		msg.Info = fmt.Sprintf("Subject: %s, %s", subject, info)
 
 		// Set Message-ID on first message so replies know what to reference
@@ -298,7 +305,7 @@ func sanitizeSubject(subject string) string {
 }
 
 // SendIssueAssignedMail composes and sends issue assigned email
-func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, tos []string) {
+func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, tos []*MailRecipient) {
 	SendAsyncs(composeIssueCommentMessages(&mailCommentContext{
 		Issue:      issue,
 		Doer:       doer,
diff --git a/services/mailer/mail_comment.go b/services/mailer/mail_comment.go
index 2f166720dbd64..ffd5b938f80ee 100644
--- a/services/mailer/mail_comment.go
+++ b/services/mailer/mail_comment.go
@@ -9,18 +9,13 @@ import (
 	"code.gitea.io/gitea/modules/log"
 )
 
-// MailParticipantsComment sends new comment emails to repository watchers
-// and mentioned people.
-func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*models.User) error {
-	return mailParticipantsComment(c, opType, issue, mentions)
-}
-
-func mailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*models.User) (err error) {
+// MailParticipantsComment sends new comment emails to repository watchers and mentioned people.
+func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*MailRecipient) error {
 	mentionedIDs := make([]int64, len(mentions))
 	for i, u := range mentions {
-		mentionedIDs[i] = u.ID
+		mentionedIDs[i] = u.userID
 	}
-	if err = mailIssueCommentToParticipants(
+	if err := mailIssueCommentToParticipants(
 		&mailCommentContext{
 			Issue:      issue,
 			Doer:       c.Poster,
@@ -34,10 +29,10 @@ func mailParticipantsComment(c *models.Comment, opType models.ActionType, issue
 }
 
 // MailMentionsComment sends email to users mentioned in a code comment
-func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*models.User) (err error) {
+func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*MailRecipient) (err error) {
 	mentionedIDs := make([]int64, len(mentions))
 	for i, u := range mentions {
-		mentionedIDs[i] = u.ID
+		mentionedIDs[i] = u.userID
 	}
 	visited := make(map[int64]bool, len(mentions)+1)
 	visited[c.Poster.ID] = true
diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index b600060a67f5e..d247bfb6a5057 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -137,12 +137,7 @@ func mailIssueCommentBatch(ctx *mailCommentContext, ids []int64, visited map[int
 		}
 		recipients = recipients[:idx]
 
-		// TODO: Separate recipients by language for i18n mail templates
-		tos := make([]string, len(recipients))
-		for i := range recipients {
-			tos[i] = recipients[i].Email
-		}
-		SendAsyncs(composeIssueCommentMessages(ctx, tos, fromMention, "issue comments"))
+		SendAsyncs(composeIssueCommentMessages(ctx, UsersToMailRecipients(recipients), fromMention, "issue comments"))
 	}
 	return nil
 }
diff --git a/services/mailer/mail_test.go b/services/mailer/mail_test.go
index d7d02d9dee822..2454f86e14686 100644
--- a/services/mailer/mail_test.go
+++ b/services/mailer/mail_test.go
@@ -57,7 +57,7 @@ func TestComposeIssueCommentMessage(t *testing.T) {
 	btpl := template.Must(template.New("issue/comment").Parse(bodyTpl))
 	InitMailRender(stpl, btpl)
 
-	tos := []string{"test@gitea.com", "test2@gitea.com"}
+	tos := []*MailRecipient{{Mail: "test@gitea.com"}, {Mail: "test2@gitea.com"}}
 	msgs := composeIssueCommentMessages(&mailCommentContext{Issue: issue, Doer: doer, ActionType: models.ActionCommentIssue,
 		Content: "test body", Comment: comment}, tos, false, "issue comment")
 	assert.Len(t, msgs, 2)
@@ -91,7 +91,7 @@ func TestComposeIssueMessage(t *testing.T) {
 	btpl := template.Must(template.New("issue/new").Parse(bodyTpl))
 	InitMailRender(stpl, btpl)
 
-	tos := []string{"test@gitea.com", "test2@gitea.com"}
+	tos := []*MailRecipient{{Mail: "test@gitea.com"}, {Mail: "test2@gitea.com"}}
 	msgs := composeIssueCommentMessages(&mailCommentContext{Issue: issue, Doer: doer, ActionType: models.ActionCreateIssue,
 		Content: "test body"}, tos, false, "issue create")
 	assert.Len(t, msgs, 2)
@@ -218,7 +218,12 @@ func TestTemplateServices(t *testing.T) {
 }
 
 func testComposeIssueCommentMessage(t *testing.T, ctx *mailCommentContext, tos []string, fromMention bool, info string) *Message {
-	msgs := composeIssueCommentMessages(ctx, tos, fromMention, info)
+	recipients := make([]*MailRecipient, len(tos))
+	assert.Len(t, tos, len(recipients))
+	for i, to := range tos {
+		recipients[i] = &MailRecipient{Mail: to}
+	}
+	msgs := composeIssueCommentMessages(ctx, recipients, fromMention, info)
 	assert.Len(t, msgs, 1)
 	return msgs[0]
 }

From c93b9f890eedd9cd49ee024dfc10641a85bdf7dd Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 20:37:40 +0100
Subject: [PATCH 04/22] code format

---
 services/mailer/mail.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index e63857d8ae8ff..ca086008326ae 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -256,10 +256,10 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 	}
 
 	var mailSubject bytes.Buffer
-	if err := subjectTemplates.ExecuteTemplate(&mailSubject, string(tplName), mailMeta); err == nil {
+	if err := subjectTemplates.ExecuteTemplate(&mailSubject, tplName, mailMeta); err == nil {
 		subject = sanitizeSubject(mailSubject.String())
 	} else {
-		log.Error("ExecuteTemplate [%s]: %v", string(tplName)+"/subject", err)
+		log.Error("ExecuteTemplate [%s]: %v", tplName+"/subject", err)
 	}
 
 	if subject == "" {
@@ -272,8 +272,8 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 
 	var mailBody bytes.Buffer
 
-	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplName), mailMeta); err != nil {
-		log.Error("ExecuteTemplate [%s]: %v", string(tplName)+"/body", err)
+	if err := bodyTemplates.ExecuteTemplate(&mailBody, tplName, mailMeta); err != nil {
+		log.Error("ExecuteTemplate [%s]: %v", tplName+"/body", err)
 	}
 
 	// Make sure to compose independent messages to avoid leaking user emails

From 02ceed79f4ee8714dca8d3ef4128f7c7922a3199 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 21:06:21 +0100
Subject: [PATCH 05/22] TODOs for "i18n"

---
 services/mailer/mail.go      | 14 +++++++++++---
 services/mailer/mail_repo.go | 37 ++++++++++++++++++++++++++----------
 2 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index ca086008326ae..d12f3ca6f166b 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -93,6 +93,7 @@ func sendUserMail(language string, u *models.User, tpl base.TplName, code, subje
 
 	var content bytes.Buffer
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&content, string(tpl), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -134,6 +135,7 @@ func SendActivateEmailMail(u *models.User, email *models.EmailAddress) {
 
 	var content bytes.Buffer
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthActivateEmail), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -160,6 +162,7 @@ func SendRegisterNotifyMail(u *models.User) {
 
 	var content bytes.Buffer
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthRegisterNotify), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -174,6 +177,7 @@ func SendRegisterNotifyMail(u *models.User) {
 // SendCollaboratorMail sends mail notification to new collaborator.
 func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *models.Repository) {
 	repoName := repo.FullName()
+	// TODO: i18n
 	subject := fmt.Sprintf("%s added you to %s", doer.DisplayName(), repoName)
 
 	data := map[string]interface{}{
@@ -184,6 +188,7 @@ func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *mod
 
 	var content bytes.Buffer
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailNotifyCollaborator), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -221,8 +226,8 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 
 	// This is the body of the new issue or comment, not the mail body
 	body := string(markup.RenderByType(markdown.MarkupName, []byte(ctx.Content), ctx.Issue.Repo.HTMLURL(), ctx.Issue.Repo.ComposeMetas()))
-
-	actType, actName, tplName := actionToTemplate(ctx.Issue, ctx.ActionType, commentType, reviewType)
+	// TODO: i18n
+	actType, actName, tplName := actionToTemplate("", ctx.Issue, ctx.ActionType, commentType, reviewType)
 
 	if actName != "new" {
 		prefix = "Re: "
@@ -256,6 +261,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 	}
 
 	var mailSubject bytes.Buffer
+	// TODO: i18n
 	if err := subjectTemplates.ExecuteTemplate(&mailSubject, tplName, mailMeta); err == nil {
 		subject = sanitizeSubject(mailSubject.String())
 	} else {
@@ -272,6 +278,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 
 	var mailBody bytes.Buffer
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&mailBody, tplName, mailMeta); err != nil {
 		log.Error("ExecuteTemplate [%s]: %v", tplName+"/body", err)
 	}
@@ -317,7 +324,8 @@ func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content strin
 
 // actionToTemplate returns the type and name of the action facing the user
 // (slightly different from models.ActionType) and the name of the template to use (based on availability)
-func actionToTemplate(issue *models.Issue, actionType models.ActionType,
+// TODO: i18n
+func actionToTemplate(lang string, issue *models.Issue, actionType models.ActionType,
 	commentType models.CommentType, reviewType models.ReviewType) (typeName, name, template string) {
 	if issue.IsPull {
 		typeName = "pull"
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index b9d24f4334d92..10c6f7fdc2785 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -13,11 +13,6 @@ import (
 
 // SendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created
 func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Repository) error {
-	var (
-		emails      []string
-		destination string
-		content     bytes.Buffer
-	)
 
 	if newOwner.IsOrganization() {
 		users, err := models.GetUsersWhoCanCreateOrgRepo(newOwner.ID)
@@ -25,15 +20,36 @@ func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Reposi
 			return err
 		}
 
-		for i := range users {
-			emails = append(emails, users[i].Email)
+		langMap := make(map[string][]string)
+		for _, user := range users {
+			langMap[user.Language] = append(langMap[user.Language], user.Email)
+		}
+
+		for k, v := range langMap {
+			if err := sendRepoTransferNotifyMailPerLang(k, newOwner, doer, v, repo); err != nil {
+				return err
+			}
 		}
+
+		return nil
+	}
+
+	return sendRepoTransferNotifyMailPerLang(newOwner.Language, newOwner, doer, []string{newOwner.Email}, repo)
+}
+
+// sendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created for each language
+func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *models.User, emails []string, repo *models.Repository) error {
+	var (
+		content bytes.Buffer
+	)
+
+	// TODO: i18n
+	destination := "you"
+	if newOwner.IsOrganization() {
 		destination = newOwner.DisplayName()
-	} else {
-		emails = []string{newOwner.Email}
-		destination = "you"
 	}
 
+	// TODO: i18n
 	subject := fmt.Sprintf("%s would like to transfer \"%s\" to %s", doer.DisplayName(), repo.FullName(), destination)
 	data := map[string]interface{}{
 		"Doer":    doer,
@@ -45,6 +61,7 @@ func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Reposi
 		"Destination": destination,
 	}
 
+	// TODO: i18n
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailRepoTransferNotify), data); err != nil {
 		return err
 	}

From 22d978cd0e6bb4b2261ec28cf7e1534324db8c6f Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sat, 20 Mar 2021 21:14:05 +0100
Subject: [PATCH 06/22] clean

---
 services/mailer/mail.go | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index d12f3ca6f166b..2686ec9589e3f 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -105,12 +105,6 @@ func sendUserMail(language string, u *models.User, tpl base.TplName, code, subje
 	SendAsync(msg)
 }
 
-// Locale represents an interface to translation
-type Locale interface {
-	Language() string
-	Tr(string, ...interface{}) string
-}
-
 // SendActivateAccountMail sends an activation mail to the user (new user registration)
 func SendActivateAccountMail(lang string, u *models.User) {
 	locale := translation.NewLocale(lang)

From f9fec7b60cfc340749601ecec640bb868d92917c Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 15:34:20 +0100
Subject: [PATCH 07/22] no fallback for lang -> just use english

---
 modules/translation/translation.go | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/modules/translation/translation.go b/modules/translation/translation.go
index f9ab035e1f7c8..b7276e53c0149 100644
--- a/modules/translation/translation.go
+++ b/modules/translation/translation.go
@@ -90,10 +90,6 @@ type locale struct {
 
 // NewLocale return a locale
 func NewLocale(lang string) Locale {
-	if len(lang) != 5 {
-		// TODO: default language
-		lang = allLangs[0].Lang
-	}
 	return &locale{
 		Lang: lang,
 	}

From 227f93b01a1b90b753ec3d76e413670638d86299 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 10:06:05 +0100
Subject: [PATCH 08/22] lint

---
 services/mailer/mail.go | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 2686ec9589e3f..f70d712eec1ab 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -47,13 +47,14 @@ var (
 	subjectRemoveSpaces = regexp.MustCompile(`[\s]+`)
 )
 
+// MailRecipient represent a mail recipient
 type MailRecipient struct {
 	userID   int64
 	Mail     string
 	Language string
 }
 
-// Convert User into MailRecipient
+// UserToMailRecipient convert User into MailRecipient
 func UserToMailRecipient(user *models.User) *MailRecipient {
 	return &MailRecipient{
 		userID:   user.ID,
@@ -62,7 +63,7 @@ func UserToMailRecipient(user *models.User) *MailRecipient {
 	}
 }
 
-// Convert list of User into list of MailRecipient
+// UsersToMailRecipients convert list of User into list of MailRecipient
 func UsersToMailRecipients(users []*models.User) []*MailRecipient {
 	recipients := make([]*MailRecipient, len(users))
 	for i := range users {

From 6cfe732fe0ad9d5b41a6547de6c71e5132882ca9 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 15:57:59 +0100
Subject: [PATCH 09/22] exec testComposeIssueCommentMessage per lang and use
 only emails

---
 services/mailer/mail.go       | 31 +++++++++++++++++++------------
 services/mailer/mail_issue.go |  9 ++++++++-
 services/mailer/mail_repo.go  |  4 ++--
 services/mailer/mail_test.go  | 15 +++++----------
 4 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index f70d712eec1ab..9f1e44d603e19 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -195,7 +195,7 @@ func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *mod
 	SendAsync(msg)
 }
 
-func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailRecipient, fromMention bool, info string) []*Message {
+func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []string, fromMention bool, info string) []*Message {
 
 	var (
 		subject string
@@ -279,9 +279,9 @@ func composeIssueCommentMessages(ctx *mailCommentContext, recipients []*MailReci
 	}
 
 	// Make sure to compose independent messages to avoid leaking user emails
-	msgs := make([]*Message, 0, len(recipients))
-	for _, to := range recipients {
-		msg := NewMessageFrom([]string{to.Mail}, ctx.Doer.DisplayName(), setting.MailService.FromEmail, subject, mailBody.String())
+	msgs := make([]*Message, 0, len(tos))
+	for _, to := range tos {
+		msg := NewMessageFrom([]string{to}, ctx.Doer.DisplayName(), setting.MailService.FromEmail, subject, mailBody.String())
 		msg.Info = fmt.Sprintf("Subject: %s, %s", subject, info)
 
 		// Set Message-ID on first message so replies know what to reference
@@ -307,14 +307,21 @@ func sanitizeSubject(subject string) string {
 }
 
 // SendIssueAssignedMail composes and sends issue assigned email
-func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, tos []*MailRecipient) {
-	SendAsyncs(composeIssueCommentMessages(&mailCommentContext{
-		Issue:      issue,
-		Doer:       doer,
-		ActionType: models.ActionType(0),
-		Content:    content,
-		Comment:    comment,
-	}, tos, false, "issue assigned"))
+func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, recipients []*MailRecipient) {
+	langMap := make(map[string][]string)
+	for _, user := range recipients {
+		langMap[user.Language] = append(langMap[user.Language], user.Mail)
+	}
+
+	for lang, tos := range langMap {
+		SendAsyncs(composeIssueCommentMessages(&mailCommentContext{
+			Issue:      issue,
+			Doer:       doer,
+			ActionType: models.ActionType(0),
+			Content:    content,
+			Comment:    comment,
+		}, lang, tos, false, "issue assigned"))
+	}
 }
 
 // actionToTemplate returns the type and name of the action facing the user
diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index d247bfb6a5057..fd0e01cfba485 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -137,7 +137,14 @@ func mailIssueCommentBatch(ctx *mailCommentContext, ids []int64, visited map[int
 		}
 		recipients = recipients[:idx]
 
-		SendAsyncs(composeIssueCommentMessages(ctx, UsersToMailRecipients(recipients), fromMention, "issue comments"))
+		langMap := make(map[string][]string)
+		for _, user := range recipients {
+			langMap[user.Language] = append(langMap[user.Language], user.Email)
+		}
+
+		for lang, tos := range langMap {
+			SendAsyncs(composeIssueCommentMessages(ctx, lang, tos, fromMention, "issue comments"))
+		}
 	}
 	return nil
 }
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index 10c6f7fdc2785..2df6593e38e44 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -25,8 +25,8 @@ func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Reposi
 			langMap[user.Language] = append(langMap[user.Language], user.Email)
 		}
 
-		for k, v := range langMap {
-			if err := sendRepoTransferNotifyMailPerLang(k, newOwner, doer, v, repo); err != nil {
+		for lang, tos := range langMap {
+			if err := sendRepoTransferNotifyMailPerLang(lang, newOwner, doer, tos, repo); err != nil {
 				return err
 			}
 		}
diff --git a/services/mailer/mail_test.go b/services/mailer/mail_test.go
index 2454f86e14686..9eef084408dff 100644
--- a/services/mailer/mail_test.go
+++ b/services/mailer/mail_test.go
@@ -57,9 +57,9 @@ func TestComposeIssueCommentMessage(t *testing.T) {
 	btpl := template.Must(template.New("issue/comment").Parse(bodyTpl))
 	InitMailRender(stpl, btpl)
 
-	tos := []*MailRecipient{{Mail: "test@gitea.com"}, {Mail: "test2@gitea.com"}}
+	tos := []string{"test@gitea.com", "test2@gitea.com"}
 	msgs := composeIssueCommentMessages(&mailCommentContext{Issue: issue, Doer: doer, ActionType: models.ActionCommentIssue,
-		Content: "test body", Comment: comment}, tos, false, "issue comment")
+		Content: "test body", Comment: comment}, "en-US", tos, false, "issue comment")
 	assert.Len(t, msgs, 2)
 	gomailMsg := msgs[0].ToMessage()
 	mailto := gomailMsg.GetHeader("To")
@@ -91,9 +91,9 @@ func TestComposeIssueMessage(t *testing.T) {
 	btpl := template.Must(template.New("issue/new").Parse(bodyTpl))
 	InitMailRender(stpl, btpl)
 
-	tos := []*MailRecipient{{Mail: "test@gitea.com"}, {Mail: "test2@gitea.com"}}
+	tos := []string{"test@gitea.com", "test2@gitea.com"}
 	msgs := composeIssueCommentMessages(&mailCommentContext{Issue: issue, Doer: doer, ActionType: models.ActionCreateIssue,
-		Content: "test body"}, tos, false, "issue create")
+		Content: "test body"}, "en-US", tos, false, "issue create")
 	assert.Len(t, msgs, 2)
 
 	gomailMsg := msgs[0].ToMessage()
@@ -218,12 +218,7 @@ func TestTemplateServices(t *testing.T) {
 }
 
 func testComposeIssueCommentMessage(t *testing.T, ctx *mailCommentContext, tos []string, fromMention bool, info string) *Message {
-	recipients := make([]*MailRecipient, len(tos))
-	assert.Len(t, tos, len(recipients))
-	for i, to := range tos {
-		recipients[i] = &MailRecipient{Mail: to}
-	}
-	msgs := composeIssueCommentMessages(ctx, recipients, fromMention, info)
+	msgs := composeIssueCommentMessages(ctx, "en-US", tos, fromMention, info)
 	assert.Len(t, msgs, 1)
 	return msgs[0]
 }

From d4040c09b62d28a103cae216bc3dc64157cac8a3 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 20:28:40 +0100
Subject: [PATCH 10/22] rm MailRecipient

---
 modules/notification/mail/mail.go | 10 ++++-----
 routers/repo/setting.go           |  2 +-
 services/mailer/mail.go           | 35 +++++--------------------------
 services/mailer/mail_comment.go   |  8 +++----
 4 files changed, 15 insertions(+), 40 deletions(-)

diff --git a/modules/notification/mail/mail.go b/modules/notification/mail/mail.go
index 24d112d808803..9c000da0f6c71 100644
--- a/modules/notification/mail/mail.go
+++ b/modules/notification/mail/mail.go
@@ -41,7 +41,7 @@ func (m *mailNotifier) NotifyCreateIssueComment(doer *models.User, repo *models.
 		act = 0
 	}
 
-	if err := mailer.MailParticipantsComment(comment, act, issue, mailer.UsersToMailRecipients(mentions)); err != nil {
+	if err := mailer.MailParticipantsComment(comment, act, issue, mentions); err != nil {
 		log.Error("MailParticipantsComment: %v", err)
 	}
 }
@@ -89,13 +89,13 @@ func (m *mailNotifier) NotifyPullRequestReview(pr *models.PullRequest, r *models
 	} else if comment.Type == models.CommentTypeComment {
 		act = models.ActionCommentPull
 	}
-	if err := mailer.MailParticipantsComment(comment, act, pr.Issue, mailer.UsersToMailRecipients(mentions)); err != nil {
+	if err := mailer.MailParticipantsComment(comment, act, pr.Issue, mentions); err != nil {
 		log.Error("MailParticipantsComment: %v", err)
 	}
 }
 
 func (m *mailNotifier) NotifyPullRequestCodeComment(pr *models.PullRequest, comment *models.Comment, mentions []*models.User) {
-	if err := mailer.MailMentionsComment(pr, comment, mailer.UsersToMailRecipients(mentions)); err != nil {
+	if err := mailer.MailMentionsComment(pr, comment, mentions); err != nil {
 		log.Error("MailMentionsComment: %v", err)
 	}
 }
@@ -104,14 +104,14 @@ func (m *mailNotifier) NotifyIssueChangeAssignee(doer *models.User, issue *model
 	// mail only sent to added assignees and not self-assignee
 	if !removed && doer.ID != assignee.ID && assignee.EmailNotifications() == models.EmailNotificationsEnabled {
 		ct := fmt.Sprintf("Assigned #%d.", issue.Index)
-		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*mailer.MailRecipient{mailer.UserToMailRecipient(assignee)})
+		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*models.User{assignee})
 	}
 }
 
 func (m *mailNotifier) NotifyPullReviewRequest(doer *models.User, issue *models.Issue, reviewer *models.User, isRequest bool, comment *models.Comment) {
 	if isRequest && doer.ID != reviewer.ID && reviewer.EmailNotifications() == models.EmailNotificationsEnabled {
 		ct := fmt.Sprintf("Requested to review %s.", issue.HTMLURL())
-		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*mailer.MailRecipient{mailer.UserToMailRecipient(reviewer)})
+		mailer.SendIssueAssignedMail(issue, doer, ct, comment, []*models.User{reviewer})
 	}
 }
 
diff --git a/routers/repo/setting.go b/routers/repo/setting.go
index 805c90004d013..dc14b69b3b0b0 100644
--- a/routers/repo/setting.go
+++ b/routers/repo/setting.go
@@ -684,7 +684,7 @@ func CollaborationPost(ctx *context.Context) {
 	}
 
 	if setting.Service.EnableNotifyMail {
-		mailer.SendCollaboratorMail(mailer.UserToMailRecipient(u), ctx.User, ctx.Repo.Repository)
+		mailer.SendCollaboratorMail(u, ctx.User, ctx.Repo.Repository)
 	}
 
 	ctx.Flash.Success(ctx.Tr("repo.settings.add_collaborator_success"))
diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 9f1e44d603e19..ef4e6d654fdfb 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -47,31 +47,6 @@ var (
 	subjectRemoveSpaces = regexp.MustCompile(`[\s]+`)
 )
 
-// MailRecipient represent a mail recipient
-type MailRecipient struct {
-	userID   int64
-	Mail     string
-	Language string
-}
-
-// UserToMailRecipient convert User into MailRecipient
-func UserToMailRecipient(user *models.User) *MailRecipient {
-	return &MailRecipient{
-		userID:   user.ID,
-		Mail:     user.Email,
-		Language: user.Language,
-	}
-}
-
-// UsersToMailRecipients convert list of User into list of MailRecipient
-func UsersToMailRecipients(users []*models.User) []*MailRecipient {
-	recipients := make([]*MailRecipient, len(users))
-	for i := range users {
-		recipients[i] = UserToMailRecipient(users[i])
-	}
-	return recipients
-}
-
 // InitMailRender initializes the mail renderer
 func InitMailRender(subjectTpl *texttmpl.Template, bodyTpl *template.Template) {
 	subjectTemplates = subjectTpl
@@ -170,7 +145,7 @@ func SendRegisterNotifyMail(u *models.User) {
 }
 
 // SendCollaboratorMail sends mail notification to new collaborator.
-func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *models.Repository) {
+func SendCollaboratorMail(recipient, doer *models.User, repo *models.Repository) {
 	repoName := repo.FullName()
 	// TODO: i18n
 	subject := fmt.Sprintf("%s added you to %s", doer.DisplayName(), repoName)
@@ -189,8 +164,8 @@ func SendCollaboratorMail(recipient *MailRecipient, doer *models.User, repo *mod
 		return
 	}
 
-	msg := NewMessage([]string{recipient.Mail}, subject, content.String())
-	msg.Info = fmt.Sprintf("UID: %d, add collaborator", recipient.userID)
+	msg := NewMessage([]string{recipient.Email}, subject, content.String())
+	msg.Info = fmt.Sprintf("UID: %d, add collaborator", recipient.ID)
 
 	SendAsync(msg)
 }
@@ -307,10 +282,10 @@ func sanitizeSubject(subject string) string {
 }
 
 // SendIssueAssignedMail composes and sends issue assigned email
-func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, recipients []*MailRecipient) {
+func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content string, comment *models.Comment, recipients []*models.User) {
 	langMap := make(map[string][]string)
 	for _, user := range recipients {
-		langMap[user.Language] = append(langMap[user.Language], user.Mail)
+		langMap[user.Language] = append(langMap[user.Language], user.Email)
 	}
 
 	for lang, tos := range langMap {
diff --git a/services/mailer/mail_comment.go b/services/mailer/mail_comment.go
index ffd5b938f80ee..9d63e5676705f 100644
--- a/services/mailer/mail_comment.go
+++ b/services/mailer/mail_comment.go
@@ -10,10 +10,10 @@ import (
 )
 
 // MailParticipantsComment sends new comment emails to repository watchers and mentioned people.
-func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*MailRecipient) error {
+func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*models.User) error {
 	mentionedIDs := make([]int64, len(mentions))
 	for i, u := range mentions {
-		mentionedIDs[i] = u.userID
+		mentionedIDs[i] = u.ID
 	}
 	if err := mailIssueCommentToParticipants(
 		&mailCommentContext{
@@ -29,10 +29,10 @@ func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue
 }
 
 // MailMentionsComment sends email to users mentioned in a code comment
-func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*MailRecipient) (err error) {
+func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*models.User) (err error) {
 	mentionedIDs := make([]int64, len(mentions))
 	for i, u := range mentions {
-		mentionedIDs[i] = u.userID
+		mentionedIDs[i] = u.ID
 	}
 	visited := make(map[int64]bool, len(mentions)+1)
 	visited[c.Poster.ID] = true

From eef62bb0b84927b5597e356df2ff1c104170109e Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 20:40:27 +0100
Subject: [PATCH 11/22] Dont reload from users from db if you alredy have in
 ram

---
 services/mailer/mail_comment.go | 12 +-----
 services/mailer/mail_issue.go   | 68 ++++++++++++++++++---------------
 2 files changed, 39 insertions(+), 41 deletions(-)

diff --git a/services/mailer/mail_comment.go b/services/mailer/mail_comment.go
index 9d63e5676705f..f73c9fb6372f9 100644
--- a/services/mailer/mail_comment.go
+++ b/services/mailer/mail_comment.go
@@ -11,10 +11,6 @@ import (
 
 // MailParticipantsComment sends new comment emails to repository watchers and mentioned people.
 func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue *models.Issue, mentions []*models.User) error {
-	mentionedIDs := make([]int64, len(mentions))
-	for i, u := range mentions {
-		mentionedIDs[i] = u.ID
-	}
 	if err := mailIssueCommentToParticipants(
 		&mailCommentContext{
 			Issue:      issue,
@@ -22,7 +18,7 @@ func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue
 			ActionType: opType,
 			Content:    c.Content,
 			Comment:    c,
-		}, mentionedIDs); err != nil {
+		}, mentions); err != nil {
 		log.Error("mailIssueCommentToParticipants: %v", err)
 	}
 	return nil
@@ -30,10 +26,6 @@ func MailParticipantsComment(c *models.Comment, opType models.ActionType, issue
 
 // MailMentionsComment sends email to users mentioned in a code comment
 func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*models.User) (err error) {
-	mentionedIDs := make([]int64, len(mentions))
-	for i, u := range mentions {
-		mentionedIDs[i] = u.ID
-	}
 	visited := make(map[int64]bool, len(mentions)+1)
 	visited[c.Poster.ID] = true
 	if err = mailIssueCommentBatch(
@@ -43,7 +35,7 @@ func MailMentionsComment(pr *models.PullRequest, c *models.Comment, mentions []*
 			ActionType: models.ActionCommentPull,
 			Content:    c.Content,
 			Comment:    c,
-		}, mentionedIDs, visited, true); err != nil {
+		}, mentions, visited, true); err != nil {
 		log.Error("mailIssueCommentBatch: %v", err)
 	}
 	return nil
diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index fd0e01cfba485..519afa3b442f1 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -23,11 +23,15 @@ type mailCommentContext struct {
 	Comment    *models.Comment
 }
 
+const (
+	MailBatchSize = 100
+)
+
 // mailIssueCommentToParticipants can be used for both new issue creation and comment.
 // This function sends two list of emails:
 // 1. Repository watchers and users who are participated in comments.
 // 2. Users who are not in 1. but get mentioned in current issue/comment.
-func mailIssueCommentToParticipants(ctx *mailCommentContext, mentions []int64) error {
+func mailIssueCommentToParticipants(ctx *mailCommentContext, mentions []*models.User) error {
 
 	// Required by the mail composer; make sure to load these before calling the async function
 	if err := ctx.Issue.LoadRepo(); err != nil {
@@ -94,34 +98,44 @@ func mailIssueCommentToParticipants(ctx *mailCommentContext, mentions []int64) e
 		visited[i] = true
 	}
 
-	if err = mailIssueCommentBatch(ctx, unfiltered, visited, false); err != nil {
+	unfilteredUsers, err := models.GetMaileableUsersByIDs(unfiltered, false)
+	if err != nil {
+		return err
+	}
+	if err = mailIssueCommentBatch(ctx, unfilteredUsers, visited, false); err != nil {
 		return fmt.Errorf("mailIssueCommentBatch(): %v", err)
 	}
 
 	return nil
 }
 
-func mailIssueCommentBatch(ctx *mailCommentContext, ids []int64, visited map[int64]bool, fromMention bool) error {
-	const batchSize = 100
-	for i := 0; i < len(ids); i += batchSize {
+func mailIssueCommentBatch(ctx *mailCommentContext, users []*models.User, visited map[int64]bool, fromMention bool) error {
+	receivers := make([]*models.User, 0, len(users))
+	for i := range users {
+		// if user has all mails enabled ...
+		if users[i].EmailNotificationsPreference == models.EmailNotificationsEnabled ||
+			// else if user only get mail on mention and this is one ...
+			fromMention && users[i].EmailNotificationsPreference == models.EmailNotificationsOnMention {
+			// ... add to mail relievers
+			receivers = append(receivers, users[i])
+		}
+	}
+
+	for i := 0; i < len(receivers); i += MailBatchSize {
 		var last int
-		if i+batchSize < len(ids) {
-			last = i + batchSize
+		if i+MailBatchSize < len(receivers) {
+			last = i + MailBatchSize
 		} else {
-			last = len(ids)
+			last = len(receivers)
 		}
-		unique := make([]int64, 0, last-i)
+
+		uniqueRecipients := make([]*models.User, 0, last-i)
 		for j := i; j < last; j++ {
-			id := ids[j]
-			if _, ok := visited[id]; !ok {
-				unique = append(unique, id)
-				visited[id] = true
+			if _, ok := visited[receivers[j].ID]; !ok {
+				uniqueRecipients = append(uniqueRecipients, receivers[j])
+				visited[receivers[j].ID] = true
 			}
 		}
-		recipients, err := models.GetMaileableUsersByIDs(unique, fromMention)
-		if err != nil {
-			return err
-		}
 
 		checkUnit := models.UnitTypeIssues
 		if ctx.Issue.IsPull {
@@ -129,16 +143,16 @@ func mailIssueCommentBatch(ctx *mailCommentContext, ids []int64, visited map[int
 		}
 		// Make sure all recipients can still see the issue
 		idx := 0
-		for _, r := range recipients {
+		for _, r := range uniqueRecipients {
 			if ctx.Issue.Repo.CheckUnitUser(r, checkUnit) {
-				recipients[idx] = r
+				uniqueRecipients[idx] = r
 				idx++
 			}
 		}
-		recipients = recipients[:idx]
+		uniqueRecipients = uniqueRecipients[:idx]
 
 		langMap := make(map[string][]string)
-		for _, user := range recipients {
+		for _, user := range uniqueRecipients {
 			langMap[user.Language] = append(langMap[user.Language], user.Email)
 		}
 
@@ -152,22 +166,14 @@ func mailIssueCommentBatch(ctx *mailCommentContext, ids []int64, visited map[int
 // MailParticipants sends new issue thread created emails to repository watchers
 // and mentioned people.
 func MailParticipants(issue *models.Issue, doer *models.User, opType models.ActionType, mentions []*models.User) error {
-	return mailParticipants(issue, doer, opType, mentions)
-}
-
-func mailParticipants(issue *models.Issue, doer *models.User, opType models.ActionType, mentions []*models.User) (err error) {
-	mentionedIDs := make([]int64, len(mentions))
-	for i, u := range mentions {
-		mentionedIDs[i] = u.ID
-	}
-	if err = mailIssueCommentToParticipants(
+	if err := mailIssueCommentToParticipants(
 		&mailCommentContext{
 			Issue:      issue,
 			Doer:       doer,
 			ActionType: opType,
 			Content:    issue.Content,
 			Comment:    nil,
-		}, mentionedIDs); err != nil {
+		}, mentions); err != nil {
 		log.Error("mailIssueCommentToParticipants: %v", err)
 	}
 	return nil

From 3ad979b036accef1328c44bf14f69fcdd05ee94b Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 21:45:09 +0100
Subject: [PATCH 12/22] nits

---
 services/mailer/mail.go         | 4 ----
 services/mailer/mail_release.go | 1 +
 services/mailer/mailer.go       | 9 ++++++---
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index ef4e6d654fdfb..cb78b1827d080 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -120,10 +120,6 @@ func SendActivateEmailMail(u *models.User, email *models.EmailAddress) {
 // SendRegisterNotifyMail triggers a notify e-mail by admin created a account.
 func SendRegisterNotifyMail(u *models.User) {
 	locale := translation.NewLocale(u.Language)
-	if setting.MailService == nil {
-		log.Warn("SendRegisterNotifyMail is being invoked but mail service hasn't been initialized")
-		return
-	}
 
 	data := map[string]interface{}{
 		"DisplayName": u.DisplayName(),
diff --git a/services/mailer/mail_release.go b/services/mailer/mail_release.go
index f278c853aebd2..1c3d95f421b80 100644
--- a/services/mailer/mail_release.go
+++ b/services/mailer/mail_release.go
@@ -41,6 +41,7 @@ func MailNewRelease(rel *models.Release) {
 	}
 
 	rel.RenderedNote = markdown.RenderString(rel.Note, rel.Repo.Link(), rel.Repo.ComposeMetas())
+	// TODO: i18n
 	subject := fmt.Sprintf("%s in %s released", rel.TagName, rel.Repo.FullName())
 
 	mailMeta := map[string]interface{}{
diff --git a/services/mailer/mailer.go b/services/mailer/mailer.go
index 2e7beffa151ab..6b86734bf845c 100644
--- a/services/mailer/mailer.go
+++ b/services/mailer/mailer.go
@@ -337,13 +337,16 @@ func NewContext() {
 
 // SendAsync send mail asynchronously
 func SendAsync(msg *Message) {
-	go func() {
-		_ = mailQueue.Push(msg)
-	}()
+	SendAsyncs([]*Message{msg})
 }
 
 // SendAsyncs send mails asynchronously
 func SendAsyncs(msgs []*Message) {
+	if setting.MailService == nil {
+		log.Error("Mailer: SendAsyncs is being invoked but mail service hasn't been initialized")
+		return
+	}
+
 	go func() {
 		for _, msg := range msgs {
 			_ = mailQueue.Push(msg)

From 388c32c33704b317c3a26dbdd54011d3f5d933c3 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 21:50:53 +0100
Subject: [PATCH 13/22] minimize diff

Signed-off-by: 6543 <6543@obermui.de>
---
 services/mailer/mail.go | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index cb78b1827d080..f76eb7b8a3e67 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -141,7 +141,7 @@ func SendRegisterNotifyMail(u *models.User) {
 }
 
 // SendCollaboratorMail sends mail notification to new collaborator.
-func SendCollaboratorMail(recipient, doer *models.User, repo *models.Repository) {
+func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 	repoName := repo.FullName()
 	// TODO: i18n
 	subject := fmt.Sprintf("%s added you to %s", doer.DisplayName(), repoName)
@@ -160,8 +160,8 @@ func SendCollaboratorMail(recipient, doer *models.User, repo *models.Repository)
 		return
 	}
 
-	msg := NewMessage([]string{recipient.Email}, subject, content.String())
-	msg.Info = fmt.Sprintf("UID: %d, add collaborator", recipient.ID)
+	msg := NewMessage([]string{u.Email}, subject, content.String())
+	msg.Info = fmt.Sprintf("UID: %d, add collaborator", u.ID)
 
 	SendAsync(msg)
 }
@@ -228,7 +228,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 
 	var mailSubject bytes.Buffer
 	// TODO: i18n
-	if err := subjectTemplates.ExecuteTemplate(&mailSubject, tplName, mailMeta); err == nil {
+	if err := subjectTemplates.ExecuteTemplate(&mailSubject, string(tplName), mailMeta); err == nil {
 		subject = sanitizeSubject(mailSubject.String())
 	} else {
 		log.Error("ExecuteTemplate [%s]: %v", tplName+"/subject", err)
@@ -245,8 +245,8 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 	var mailBody bytes.Buffer
 
 	// TODO: i18n
-	if err := bodyTemplates.ExecuteTemplate(&mailBody, tplName, mailMeta); err != nil {
-		log.Error("ExecuteTemplate [%s]: %v", tplName+"/body", err)
+	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplName), mailMeta); err != nil {
+		log.Error("ExecuteTemplate [%s]: %v", string(tplName)+"/body", err)
 	}
 
 	// Make sure to compose independent messages to avoid leaking user emails

From e8f9be5f127355f7237b1006e935b9fa65517862 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 22:27:09 +0100
Subject: [PATCH 14/22] localize subjects

---
 options/locale/locale_en-US.ini |  7 +++++++
 services/mailer/mail.go         | 12 ++++++------
 services/mailer/mail_release.go | 26 +++++++++++++++++---------
 services/mailer/mail_repo.go    |  8 ++++----
 4 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/options/locale/locale_en-US.ini b/options/locale/locale_en-US.ini
index e679e1e874979..736b6dfc93f44 100644
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@@ -320,6 +320,13 @@ reset_password = Recover your account
 register_success = Registration successful
 register_notify = Welcome to Gitea
 
+release.new.subject = %s in %s released
+
+repo.transfer.subject = %s would like to transfer "%s" to %s
+repo.transfer.to_you = you
+
+repo.collaborator.added.subject = %s added you to %s
+
 [modal]
 yes = Yes
 no = No
diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index f76eb7b8a3e67..d7e522b1d96eb 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -142,10 +142,10 @@ func SendRegisterNotifyMail(u *models.User) {
 
 // SendCollaboratorMail sends mail notification to new collaborator.
 func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
+	locale := translation.NewLocale(u.Language)
 	repoName := repo.FullName()
-	// TODO: i18n
-	subject := fmt.Sprintf("%s added you to %s", doer.DisplayName(), repoName)
 
+	subject := locale.Tr("mail.repo.collaborator.added.subject", doer.DisplayName(), repoName)
 	data := map[string]interface{}{
 		"Subject":  subject,
 		"RepoName": repoName,
@@ -169,6 +169,8 @@ func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []string, fromMention bool, info string) []*Message {
 
 	var (
+		locale = translation.NewLocale(lang)
+
 		subject string
 		link    string
 		prefix  string
@@ -192,8 +194,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 
 	// This is the body of the new issue or comment, not the mail body
 	body := string(markup.RenderByType(markdown.MarkupName, []byte(ctx.Content), ctx.Issue.Repo.HTMLURL(), ctx.Issue.Repo.ComposeMetas()))
-	// TODO: i18n
-	actType, actName, tplName := actionToTemplate("", ctx.Issue, ctx.ActionType, commentType, reviewType)
+	actType, actName, tplName := actionToTemplate(ctx.Issue, ctx.ActionType, commentType, reviewType)
 
 	if actName != "new" {
 		prefix = "Re: "
@@ -297,8 +298,7 @@ func SendIssueAssignedMail(issue *models.Issue, doer *models.User, content strin
 
 // actionToTemplate returns the type and name of the action facing the user
 // (slightly different from models.ActionType) and the name of the template to use (based on availability)
-// TODO: i18n
-func actionToTemplate(lang string, issue *models.Issue, actionType models.ActionType,
+func actionToTemplate(issue *models.Issue, actionType models.ActionType,
 	commentType models.CommentType, reviewType models.ReviewType) (typeName, name, template string) {
 	if issue.IsPull {
 		typeName = "pull"
diff --git a/services/mailer/mail_release.go b/services/mailer/mail_release.go
index 1c3d95f421b80..b60b3dd715d42 100644
--- a/services/mailer/mail_release.go
+++ b/services/mailer/mail_release.go
@@ -6,13 +6,13 @@ package mailer
 
 import (
 	"bytes"
-	"fmt"
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup/markdown"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/translation"
 )
 
 const (
@@ -33,17 +33,24 @@ func MailNewRelease(rel *models.Release) {
 		return
 	}
 
-	tos := make([]string, 0, len(recipients))
-	for _, to := range recipients {
-		if to.ID != rel.PublisherID {
-			tos = append(tos, to.Email)
+	langMap := make(map[string][]string)
+	for _, user := range recipients {
+		if user.ID != rel.PublisherID {
+			langMap[user.Language] = append(langMap[user.Language], user.Email)
 		}
 	}
 
+	for lang, tos := range langMap {
+		mailNewRelease(lang, tos, rel)
+	}
+}
+
+func mailNewRelease(lang string, tos []string, rel *models.Release) {
+	locale := translation.NewLocale(lang)
+
 	rel.RenderedNote = markdown.RenderString(rel.Note, rel.Repo.Link(), rel.Repo.ComposeMetas())
-	// TODO: i18n
-	subject := fmt.Sprintf("%s in %s released", rel.TagName, rel.Repo.FullName())
 
+	subject := locale.Tr("mail.release.new.subject", rel.TagName, rel.Repo.FullName())
 	mailMeta := map[string]interface{}{
 		"Release": rel,
 		"Subject": subject,
@@ -51,12 +58,13 @@ func MailNewRelease(rel *models.Release) {
 
 	var mailBody bytes.Buffer
 
-	if err = bodyTemplates.ExecuteTemplate(&mailBody, string(tplNewReleaseMail), mailMeta); err != nil {
+	// TODO: i18n
+	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplNewReleaseMail), mailMeta); err != nil {
 		log.Error("ExecuteTemplate [%s]: %v", string(tplNewReleaseMail)+"/body", err)
 		return
 	}
 
-	msgs := make([]*Message, 0, len(recipients))
+	msgs := make([]*Message, 0, len(tos))
 	publisherName := rel.Publisher.DisplayName()
 	relURL := "<" + rel.HTMLURL() + ">"
 	for _, to := range tos {
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index 2df6593e38e44..feaa22c4a6dfb 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 
 	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/translation"
 )
 
 // SendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created
@@ -40,17 +41,16 @@ func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Reposi
 // sendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created for each language
 func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *models.User, emails []string, repo *models.Repository) error {
 	var (
+		locale  = translation.NewLocale(lang)
 		content bytes.Buffer
 	)
 
-	// TODO: i18n
-	destination := "you"
+	destination := locale.Tr("mail.repo.transfer.to_you")
 	if newOwner.IsOrganization() {
 		destination = newOwner.DisplayName()
 	}
 
-	// TODO: i18n
-	subject := fmt.Sprintf("%s would like to transfer \"%s\" to %s", doer.DisplayName(), repo.FullName(), destination)
+	subject := locale.Tr("mail.repo.transfer.subject", doer.DisplayName(), repo.FullName(), destination)
 	data := map[string]interface{}{
 		"Doer":    doer,
 		"User":    repo.Owner,

From 66799a21d69e30132449036ba6dcd88777337cb1 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 22:29:02 +0100
Subject: [PATCH 15/22] linter ...

---
 services/mailer/mail.go       | 2 +-
 services/mailer/mail_issue.go | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index d7e522b1d96eb..58f45c91cd5cf 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -169,7 +169,7 @@ func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []string, fromMention bool, info string) []*Message {
 
 	var (
-		locale = translation.NewLocale(lang)
+		// locale = translation.NewLocale(lang)
 
 		subject string
 		link    string
diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index 519afa3b442f1..b477635be5095 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -24,6 +24,7 @@ type mailCommentContext struct {
 }
 
 const (
+	// MailBatchSize set the batch size used in mailIssueCommentBatch
 	MailBatchSize = 100
 )
 

From f2c380879d203a053d90f392fc1e1f8723fef138 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 22:38:12 +0100
Subject: [PATCH 16/22] Tr extend

---
 options/locale/locale_en-US.ini | 3 ++-
 services/mailer/mail_repo.go    | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/options/locale/locale_en-US.ini b/options/locale/locale_en-US.ini
index 736b6dfc93f44..562f9229838e4 100644
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@@ -322,7 +322,8 @@ register_notify = Welcome to Gitea
 
 release.new.subject = %s in %s released
 
-repo.transfer.subject = %s would like to transfer "%s" to %s
+repo.transfer.subject_to = %s would like to transfer "%s" to %s
+repo.transfer.subject_to_you = %s would like to transfer "%s" to you
 repo.transfer.to_you = you
 
 repo.collaborator.added.subject = %s added you to %s
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index feaa22c4a6dfb..45b5454c9e9cb 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -46,11 +46,12 @@ func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *models.User,
 	)
 
 	destination := locale.Tr("mail.repo.transfer.to_you")
+	subject := locale.Tr("mail.repo.transfer.subject_to_you", doer.DisplayName(), repo.FullName())
 	if newOwner.IsOrganization() {
 		destination = newOwner.DisplayName()
+		subject = locale.Tr("mail.repo.transfer.subject_to", doer.DisplayName(), repo.FullName(), destination)
 	}
 
-	subject := locale.Tr("mail.repo.transfer.subject", doer.DisplayName(), repo.FullName(), destination)
 	data := map[string]interface{}{
 		"Doer":    doer,
 		"User":    repo.Owner,

From 16b64b22e34f0a7a44ab85b2b8a2b3beea615433 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Sun, 21 Mar 2021 22:45:11 +0100
Subject: [PATCH 17/22] start tmpl edit ...

---
 templates/mail/notify/repo_transfer.tmpl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/templates/mail/notify/repo_transfer.tmpl b/templates/mail/notify/repo_transfer.tmpl
index 68ceded116738..e0dca8869d669 100644
--- a/templates/mail/notify/repo_transfer.tmpl
+++ b/templates/mail/notify/repo_transfer.tmpl
@@ -11,7 +11,7 @@
 	<p>
 		---
 		<br>
-		<a href="{{.Link}}">View it on Gitea</a>.
+		<a href="{{.Link}}">View it on {{AppName}}</a>.
 	</p>
 </body>
 </html>

From 0d4f499a09f412bf608faf9250bbfac81709d2c0 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Thu, 1 Apr 2021 03:06:07 +0200
Subject: [PATCH 18/22] Apply suggestions from code review

---
 services/mailer/mail.go      | 2 --
 services/mailer/mail_repo.go | 1 -
 2 files changed, 3 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 58f45c91cd5cf..3258455aa6d54 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -169,8 +169,6 @@ func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []string, fromMention bool, info string) []*Message {
 
 	var (
-		// locale = translation.NewLocale(lang)
-
 		subject string
 		link    string
 		prefix  string
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index 45b5454c9e9cb..7194e137a3c8c 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -14,7 +14,6 @@ import (
 
 // SendRepoTransferNotifyMail triggers a notification e-mail when a pending repository transfer was created
 func SendRepoTransferNotifyMail(doer, newOwner *models.User, repo *models.Repository) error {
-
 	if newOwner.IsOrganization() {
 		users, err := models.GetUsersWhoCanCreateOrgRepo(newOwner.ID)
 		if err != nil {

From 880d68ce64ebc9d376b541293bb1b50cc529c9d6 Mon Sep 17 00:00:00 2001
From: 6543 <6543@obermui.de>
Date: Thu, 1 Apr 2021 18:54:46 +0200
Subject: [PATCH 19/22] use translation.Locale

---
 routers/user/auth.go            |  8 ++++----
 routers/user/auth_openid.go     |  2 +-
 routers/user/setting/account.go |  2 +-
 services/mailer/mail.go         | 11 +++++------
 4 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/routers/user/auth.go b/routers/user/auth.go
index 6853633dd7216..9217885519f3c 100644
--- a/routers/user/auth.go
+++ b/routers/user/auth.go
@@ -1028,7 +1028,7 @@ func LinkAccountPostRegister(ctx *context.Context) {
 
 	// Send confirmation email
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
+		mailer.SendActivateAccountMail(ctx.Locale, u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
@@ -1213,7 +1213,7 @@ func SignUpPost(ctx *context.Context) {
 
 	// Send confirmation email, no need for social account.
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
+		mailer.SendActivateAccountMail(ctx.Locale, u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
@@ -1247,7 +1247,7 @@ func Activate(ctx *context.Context) {
 				ctx.Data["ResendLimited"] = true
 			} else {
 				ctx.Data["ActiveCodeLives"] = timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, ctx.Locale.Language())
-				mailer.SendActivateAccountMail(ctx.Locale.Language(), ctx.User)
+				mailer.SendActivateAccountMail(ctx.Locale, ctx.User)
 
 				if err := ctx.Cache.Put("MailResendLimit_"+ctx.User.LowerName, ctx.User.LowerName, 180); err != nil {
 					log.Error("Set cache(MailResendLimit) fail: %v", err)
@@ -1397,7 +1397,7 @@ func ForgotPasswdPost(ctx *context.Context) {
 		return
 	}
 
-	mailer.SendResetPasswordMail(u.Language, u)
+	mailer.SendResetPasswordMail(u)
 
 	if err = ctx.Cache.Put("MailResendLimit_"+u.LowerName, u.LowerName, 180); err != nil {
 		log.Error("Set cache(MailResendLimit) fail: %v", err)
diff --git a/routers/user/auth_openid.go b/routers/user/auth_openid.go
index 3064a354f6149..967e8aad2d436 100644
--- a/routers/user/auth_openid.go
+++ b/routers/user/auth_openid.go
@@ -467,7 +467,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 
 	// Send confirmation email, no need for social account.
 	if setting.Service.RegisterEmailConfirm && u.ID > 1 {
-		mailer.SendActivateAccountMail(ctx.Locale.Language(), u)
+		mailer.SendActivateAccountMail(ctx.Locale, u)
 
 		ctx.Data["IsSendRegisterMail"] = true
 		ctx.Data["Email"] = u.Email
diff --git a/routers/user/setting/account.go b/routers/user/setting/account.go
index eb33c45200c18..0bf6cf8b87283 100644
--- a/routers/user/setting/account.go
+++ b/routers/user/setting/account.go
@@ -112,7 +112,7 @@ func EmailPost(ctx *context.Context) {
 				ctx.Redirect(setting.AppSubURL + "/user/settings/account")
 				return
 			}
-			mailer.SendActivateAccountMail(ctx.Locale.Language(), ctx.User)
+			mailer.SendActivateAccountMail(ctx.Locale, ctx.User)
 			address = ctx.User.Email
 		} else {
 			id := ctx.QueryInt64("id")
diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 3258455aa6d54..94279d70d7792 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -82,15 +82,14 @@ func sendUserMail(language string, u *models.User, tpl base.TplName, code, subje
 }
 
 // SendActivateAccountMail sends an activation mail to the user (new user registration)
-func SendActivateAccountMail(lang string, u *models.User) {
-	locale := translation.NewLocale(lang)
-	sendUserMail(lang, u, mailAuthActivate, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.activate_account"), "activate account")
+func SendActivateAccountMail(locale translation.Locale, u *models.User) {
+	sendUserMail(locale.Language(), u, mailAuthActivate, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.activate_account"), "activate account")
 }
 
 // SendResetPasswordMail sends a password reset mail to the user
-func SendResetPasswordMail(lang string, u *models.User) {
-	locale := translation.NewLocale(lang)
-	sendUserMail(lang, u, mailAuthResetPassword, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.reset_password"), "recover account")
+func SendResetPasswordMail(u *models.User) {
+	locale := translation.NewLocale(u.Language)
+	sendUserMail(u.Language, u, mailAuthResetPassword, u.GenerateEmailActivateCode(u.Email), locale.Tr("mail.reset_password"), "recover account")
 }
 
 // SendActivateEmailMail sends confirmation email to confirm new email address

From 291d0e9c796617c649cc9b2f236fdebfdb67e37c Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Thu, 1 Apr 2021 21:08:57 +0100
Subject: [PATCH 20/22] improve mailIssueCommentBatch

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 services/mailer/mail_issue.go | 65 ++++++++++++++---------------------
 1 file changed, 26 insertions(+), 39 deletions(-)

diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index b477635be5095..6c2a2fe6c9fe0 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -111,56 +111,43 @@ func mailIssueCommentToParticipants(ctx *mailCommentContext, mentions []*models.
 }
 
 func mailIssueCommentBatch(ctx *mailCommentContext, users []*models.User, visited map[int64]bool, fromMention bool) error {
-	receivers := make([]*models.User, 0, len(users))
-	for i := range users {
-		// if user has all mails enabled ...
-		if users[i].EmailNotificationsPreference == models.EmailNotificationsEnabled ||
-			// else if user only get mail on mention and this is one ...
-			fromMention && users[i].EmailNotificationsPreference == models.EmailNotificationsOnMention {
-			// ... add to mail relievers
-			receivers = append(receivers, users[i])
-		}
+	checkUnit := models.UnitTypeIssues
+	if ctx.Issue.IsPull {
+		checkUnit = models.UnitTypePullRequests
 	}
 
-	for i := 0; i < len(receivers); i += MailBatchSize {
-		var last int
-		if i+MailBatchSize < len(receivers) {
-			last = i + MailBatchSize
-		} else {
-			last = len(receivers)
+	langMap := make(map[string][]string)
+	for _, user := range users {
+		// At this point we exclude:
+		// user that don't have all mails enabled or users only get mail on mention and this is one ...
+		if !(user.EmailNotificationsPreference == models.EmailNotificationsEnabled ||
+			fromMention && user.EmailNotificationsPreference == models.EmailNotificationsOnMention) {
+			continue
 		}
 
-		uniqueRecipients := make([]*models.User, 0, last-i)
-		for j := i; j < last; j++ {
-			if _, ok := visited[receivers[j].ID]; !ok {
-				uniqueRecipients = append(uniqueRecipients, receivers[j])
-				visited[receivers[j].ID] = true
-			}
+		// if we have already visited this user we exclude them
+		if _, ok := visited[user.ID]; ok {
+			continue
 		}
 
-		checkUnit := models.UnitTypeIssues
-		if ctx.Issue.IsPull {
-			checkUnit = models.UnitTypePullRequests
-		}
-		// Make sure all recipients can still see the issue
-		idx := 0
-		for _, r := range uniqueRecipients {
-			if ctx.Issue.Repo.CheckUnitUser(r, checkUnit) {
-				uniqueRecipients[idx] = r
-				idx++
-			}
-		}
-		uniqueRecipients = uniqueRecipients[:idx]
+		// now mark them as visited
+		visited[user.ID] = true
 
-		langMap := make(map[string][]string)
-		for _, user := range uniqueRecipients {
-			langMap[user.Language] = append(langMap[user.Language], user.Email)
+		// test if this user is allowed to see the issue/pull
+		if !ctx.Issue.Repo.CheckUnitUser(user, checkUnit) {
+			continue
 		}
 
-		for lang, tos := range langMap {
-			SendAsyncs(composeIssueCommentMessages(ctx, lang, tos, fromMention, "issue comments"))
+		langMap[user.Language] = append(langMap[user.Language], user.Email)
+	}
+
+	for lang, receivers := range langMap {
+		for i := ((len(receivers) - 1) / MailBatchSize) * MailBatchSize; i >= 0; i -= MailBatchSize {
+			SendAsyncs(composeIssueCommentMessages(ctx, lang, receivers[i:], fromMention, "issue comments"))
+			receivers = receivers[:i]
 		}
 	}
+
 	return nil
 }
 

From 9b527c8fed02bc997fd93cfab56f76cf0d2ed8ad Mon Sep 17 00:00:00 2001
From: Andrew Thornton <art27@cantab.net>
Date: Thu, 1 Apr 2021 21:41:21 +0100
Subject: [PATCH 21/22] add i18n to datas

Signed-off-by: Andrew Thornton <art27@cantab.net>
---
 services/mailer/mail.go         | 24 ++++++++++++++++++------
 services/mailer/mail_release.go |  8 +++++---
 services/mailer/mail_repo.go    | 15 ++++++++-------
 3 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/services/mailer/mail.go b/services/mailer/mail.go
index 94279d70d7792..c50795968aa64 100644
--- a/services/mailer/mail.go
+++ b/services/mailer/mail.go
@@ -60,16 +60,19 @@ func SendTestMail(email string) error {
 
 // sendUserMail sends a mail to the user
 func sendUserMail(language string, u *models.User, tpl base.TplName, code, subject, info string) {
+	locale := translation.NewLocale(language)
 	data := map[string]interface{}{
 		"DisplayName":       u.DisplayName(),
 		"ActiveCodeLives":   timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, language),
 		"ResetPwdCodeLives": timeutil.MinutesToFriendly(setting.Service.ResetPwdCodeLives, language),
 		"Code":              code,
+		"i18n":              locale,
+		"Language":          locale.Language(),
 	}
 
 	var content bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&content, string(tpl), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -100,11 +103,13 @@ func SendActivateEmailMail(u *models.User, email *models.EmailAddress) {
 		"ActiveCodeLives": timeutil.MinutesToFriendly(setting.Service.ActiveCodeLives, locale.Language()),
 		"Code":            u.GenerateEmailActivateCode(email.Email),
 		"Email":           email.Email,
+		"i18n":            locale,
+		"Language":        locale.Language(),
 	}
 
 	var content bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthActivateEmail), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -123,11 +128,13 @@ func SendRegisterNotifyMail(u *models.User) {
 	data := map[string]interface{}{
 		"DisplayName": u.DisplayName(),
 		"Username":    u.Name,
+		"i18n":        locale,
+		"Language":    locale.Language(),
 	}
 
 	var content bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailAuthRegisterNotify), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -149,11 +156,13 @@ func SendCollaboratorMail(u, doer *models.User, repo *models.Repository) {
 		"Subject":  subject,
 		"RepoName": repoName,
 		"Link":     repo.HTMLURL(),
+		"i18n":     locale,
+		"Language": locale.Language(),
 	}
 
 	var content bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailNotifyCollaborator), data); err != nil {
 		log.Error("Template: %v", err)
 		return
@@ -206,6 +215,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 			}
 		}
 	}
+	locale := translation.NewLocale(lang)
 
 	mailMeta := map[string]interface{}{
 		"FallbackSubject": fallback,
@@ -222,10 +232,12 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 		"ActionType":      actType,
 		"ActionName":      actName,
 		"ReviewComments":  reviewComments,
+		"i18n":            locale,
+		"Language":        locale.Language(),
 	}
 
 	var mailSubject bytes.Buffer
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := subjectTemplates.ExecuteTemplate(&mailSubject, string(tplName), mailMeta); err == nil {
 		subject = sanitizeSubject(mailSubject.String())
 	} else {
@@ -242,7 +254,7 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, tos []str
 
 	var mailBody bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplName), mailMeta); err != nil {
 		log.Error("ExecuteTemplate [%s]: %v", string(tplName)+"/body", err)
 	}
diff --git a/services/mailer/mail_release.go b/services/mailer/mail_release.go
index b60b3dd715d42..22efe2f0464b3 100644
--- a/services/mailer/mail_release.go
+++ b/services/mailer/mail_release.go
@@ -52,13 +52,15 @@ func mailNewRelease(lang string, tos []string, rel *models.Release) {
 
 	subject := locale.Tr("mail.release.new.subject", rel.TagName, rel.Repo.FullName())
 	mailMeta := map[string]interface{}{
-		"Release": rel,
-		"Subject": subject,
+		"Release":  rel,
+		"Subject":  subject,
+		"i18n":     locale,
+		"Language": locale.Language(),
 	}
 
 	var mailBody bytes.Buffer
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&mailBody, string(tplNewReleaseMail), mailMeta); err != nil {
 		log.Error("ExecuteTemplate [%s]: %v", string(tplNewReleaseMail)+"/body", err)
 		return
diff --git a/services/mailer/mail_repo.go b/services/mailer/mail_repo.go
index 7194e137a3c8c..c742101ee1961 100644
--- a/services/mailer/mail_repo.go
+++ b/services/mailer/mail_repo.go
@@ -52,16 +52,17 @@ func sendRepoTransferNotifyMailPerLang(lang string, newOwner, doer *models.User,
 	}
 
 	data := map[string]interface{}{
-		"Doer":    doer,
-		"User":    repo.Owner,
-		"Repo":    repo.FullName(),
-		"Link":    repo.HTMLURL(),
-		"Subject": subject,
-
+		"Doer":        doer,
+		"User":        repo.Owner,
+		"Repo":        repo.FullName(),
+		"Link":        repo.HTMLURL(),
+		"Subject":     subject,
+		"i18n":        locale,
+		"Language":    locale.Language(),
 		"Destination": destination,
 	}
 
-	// TODO: i18n
+	// TODO: i18n templates?
 	if err := bodyTemplates.ExecuteTemplate(&content, string(mailRepoTransferNotify), data); err != nil {
 		return err
 	}

From 1bb1ea15b047a5bd9c6cfda334c449837da8ef13 Mon Sep 17 00:00:00 2001
From: zeripath <art27@cantab.net>
Date: Fri, 2 Apr 2021 02:34:42 +0100
Subject: [PATCH 22/22] a comment

---
 services/mailer/mail_issue.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/services/mailer/mail_issue.go b/services/mailer/mail_issue.go
index 6c2a2fe6c9fe0..9786a06f62f3b 100644
--- a/services/mailer/mail_issue.go
+++ b/services/mailer/mail_issue.go
@@ -142,6 +142,9 @@ func mailIssueCommentBatch(ctx *mailCommentContext, users []*models.User, visite
 	}
 
 	for lang, receivers := range langMap {
+		// because we know that the len(receivers) > 0 and we don't care about the order particularly
+		// working backwards from the last (possibly) incomplete batch. If len(receivers) can be 0 this
+		// starting condition will need to be changed slightly
 		for i := ((len(receivers) - 1) / MailBatchSize) * MailBatchSize; i >= 0; i -= MailBatchSize {
 			SendAsyncs(composeIssueCommentMessages(ctx, lang, receivers[i:], fromMention, "issue comments"))
 			receivers = receivers[:i]