Write the issue/merge request title in the notification email subject

This changes the email subjects for issues and merge request
notifications from:

    Team / Project | Note for issue #1234

to:

    Team / Project | Saving issue doesn't work sometimes (#1234)

Rationale:

* Scan the subject of the email notification more easily when catching
up with a lot of notifications. Instead of having to open the email to
get the title of the issue or merge request, one can simply read the
subject of the email.

* Group messages by subject: email clients will group emails in threads
if they have the same subject.

app/mailers/emails/issues.rb

@@ -3,14 +3,16 @@ module Emails
     def new_issue_email(recipient_id, issue_id)
       @issue = Issue.find(issue_id)
       @project = @issue.project
-      mail(to: recipient(recipient_id), subject: subject("New issue ##{@issue.iid}", @issue.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@issue.title} (##{@issue.iid})"))
     end
 
     def reassigned_issue_email(recipient_id, issue_id, previous_assignee_id)
       @issue = Issue.find(issue_id)
       @previous_assignee = User.find_by(id: previous_assignee_id) if previous_assignee_id
       @project = @issue.project
-      mail(to: recipient(recipient_id), subject: subject("Changed issue ##{@issue.iid}", @issue.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@issue.title} (##{@issue.iid})"))
     end
 
     def closed_issue_email(recipient_id, issue_id, updated_by_user_id)
@@ -18,7 +20,7 @@ module Emails
       @project = @issue.project
       @updated_by = User.find updated_by_user_id
       mail(to: recipient(recipient_id),
-           subject: subject("Closed issue ##{@issue.iid}", @issue.title))
+           subject: subject("#{@issue.title} (##{@issue.iid})"))
     end
 
     def issue_status_changed_email(recipient_id, issue_id, status, updated_by_user_id)
@@ -27,7 +29,7 @@ module Emails
       @project = @issue.project
       @updated_by = User.find updated_by_user_id
       mail(to: recipient(recipient_id),
-           subject: subject("Changed issue ##{@issue.iid}", @issue.title))
+           subject: subject("#{@issue.title} (##{@issue.iid})"))
     end
   end
 end

app/mailers/emails/merge_requests.rb

@@ -3,27 +3,31 @@ module Emails
     def new_merge_request_email(recipient_id, merge_request_id)
       @merge_request = MergeRequest.find(merge_request_id)
       @project = @merge_request.project
-      mail(to: recipient(recipient_id), subject: subject("New merge request ##{@merge_request.iid}", @merge_request.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@merge_request.title} (!#{@merge_request.iid})"))
     end
 
     def reassigned_merge_request_email(recipient_id, merge_request_id, previous_assignee_id)
       @merge_request = MergeRequest.find(merge_request_id)
       @previous_assignee = User.find_by(id: previous_assignee_id) if previous_assignee_id
       @project = @merge_request.project
-      mail(to: recipient(recipient_id), subject: subject("Changed merge request ##{@merge_request.iid}", @merge_request.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@merge_request.title} (!#{@merge_request.iid})"))
     end
 
     def closed_merge_request_email(recipient_id, merge_request_id, updated_by_user_id)
       @merge_request = MergeRequest.find(merge_request_id)
       @updated_by = User.find updated_by_user_id
       @project = @merge_request.project
-      mail(to: recipient(recipient_id), subject: subject("Closed merge request ##{@merge_request.iid}", @merge_request.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@merge_request.title} (!#{@merge_request.iid})"))
     end
 
     def merged_merge_request_email(recipient_id, merge_request_id)
       @merge_request = MergeRequest.find(merge_request_id)
       @project = @merge_request.project
-      mail(to: recipient(recipient_id), subject: subject("Accepted merge request ##{@merge_request.iid}", @merge_request.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@merge_request.title} (!#{@merge_request.iid})"))
     end
   end
 

app/mailers/emails/notes.rb

@@ -4,27 +4,31 @@ module Emails
       @note = Note.find(note_id)
       @commit = @note.noteable
       @project = @note.project
-      mail(to: recipient(recipient_id), subject: subject("Note for commit #{@commit.short_id}", @commit.title))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@commit.title} (#{@commit.short_id})"))
     end
 
     def note_issue_email(recipient_id, note_id)
       @note = Note.find(note_id)
       @issue = @note.noteable
       @project = @note.project
-      mail(to: recipient(recipient_id), subject: subject("Note for issue ##{@issue.iid}"))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@issue.title} (##{@issue.iid})"))
     end
 
     def note_merge_request_email(recipient_id, note_id)
       @note = Note.find(note_id)
       @merge_request = @note.noteable
       @project = @note.project
-      mail(to: recipient(recipient_id), subject: subject("Note for merge request ##{@merge_request.iid}"))
+      mail(to: recipient(recipient_id),
+           subject: subject("#{@merge_request.title} (!#{@merge_request.iid})"))
     end
 
     def note_wall_email(recipient_id, note_id)
       @note = Note.find(note_id)
       @project = @note.project
-      mail(to: recipient(recipient_id), subject: subject("Note on wall"))
+      mail(to: recipient(recipient_id),
+           subject: subject("Note on wall"))
     end
   end
 end