Add SUBJECT_PREFIX mailer config option (#6605)

* Add SUBJECT_PREFIX mailer config option

* Add space between subject prefix and subject (Change from Gogs)

Signed-off-by: Andrew Thornton <art27@cantab.net>

4 files changed, 12 insertions, 5 deletions

diff --git a/custom/conf/app.ini.sample b/custom/conf/app.ini.sample
index 6dee39ed83..4b846d3aff 100644
--- a/custom/conf/app.ini.sample
+++ b/custom/conf/app.ini.sample
@@ -411,8 +411,8 @@ PAGING_NUM = 10
 ENABLED = false
 ; Buffer length of channel, keep it as it is if you don't know what it is.
 SEND_BUFFER_LEN = 100
-; Name displayed in mail title
-SUBJECT = %(APP_NAME)s
+; Prefix displayed before subject in mail
+SUBJECT_PREFIX =
 ; Mail server
 ; Gmail: smtp.gmail.com:587
 ; QQ: smtp.qq.com:465
diff --git a/docs/content/doc/advanced/config-cheat-sheet.en-us.md b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
index 1e97f93e13..8ae89ef4de 100644
--- a/docs/content/doc/advanced/config-cheat-sheet.en-us.md
+++ b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
@@ -241,14 +241,15 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `PASSWD`: **\<empty\>**: Password of mailing user.  Use \`your password\` for quoting if you use special characters in the password.
 - `SKIP_VERIFY`: **\<empty\>**: Do not verify the self-signed certificates.
    - **Note:** Gitea only supports SMTP with STARTTLS.
+- `SUBJECT_PREFIX`: **\<empty\>**: Prefix to be placed before e-mail subject lines.
 - `MAILER_TYPE`: **smtp**: \[smtp, sendmail, dummy\]
    - **smtp** Use SMTP to send mail
    - **sendmail** Use the operating system's `sendmail` command instead of SMTP.
    This is common on linux systems.
    - **dummy** Send email messages to the log as a testing phase.
    - Note that enabling sendmail will ignore all other `mailer` settings except `ENABLED`,
-     `FROM` and `SENDMAIL_PATH`.
-   - Enabling dummy will ignore all settings except `ENABLED` and `FROM`.
+     `FROM`, `SUBJECT_PREFIX` and `SENDMAIL_PATH`.
+   - Enabling dummy will ignore all settings except `ENABLED`, `SUBJECT_PREFIX` and `FROM`.
 - `SENDMAIL_PATH`: **sendmail**: The location of sendmail on the operating system (can be
    command or full path).
 - ``IS_TLS_ENABLED`` :  **false** : Decide if SMTP connections should use TLS.
diff --git a/modules/mailer/mailer.go b/modules/mailer/mailer.go
index 84da0d4c17..411d6eafd8 100644
--- a/modules/mailer/mailer.go
+++ b/modules/mailer/mailer.go
@@ -38,7 +38,11 @@ func NewMessageFrom(to []string, fromDisplayName, fromAddress, subject, body str
 	msg := gomail.NewMessage()
 	msg.SetAddressHeader("From", fromAddress, fromDisplayName)
 	msg.SetHeader("To", to...)
-	msg.SetHeader("Subject", subject)
+	if len(setting.MailService.SubjectPrefix) > 0 {
+		msg.SetHeader("Subject", setting.MailService.SubjectPrefix+" "+subject)
+	} else {
+		msg.SetHeader("Subject", subject)
+	}
 	msg.SetDateHeader("Date", time.Now())
 	msg.SetHeader("X-Auto-Response-Suppress", "All")
 
diff --git a/modules/setting/mailer.go b/modules/setting/mailer.go
index e627aef017..3101ed5452 100644
--- a/modules/setting/mailer.go
+++ b/modules/setting/mailer.go
@@ -21,6 +21,7 @@ type Mailer struct {
 	FromEmail       string
 	SendAsPlainText bool
 	MailerType      string
+	SubjectPrefix   string
 
 	// SMTP sender
 	Host              string
@@ -65,6 +66,7 @@ func newMailService() {
 		CertFile:       sec.Key("CERT_FILE").String(),
 		KeyFile:        sec.Key("KEY_FILE").String(),
 		IsTLSEnabled:   sec.Key("IS_TLS_ENABLED").MustBool(),
+		SubjectPrefix:  sec.Key("SUBJECT_PREFIX").MustString(""),
 
 		SendmailPath: sec.Key("SENDMAIL_PATH").MustString("sendmail"),
 	}