Fix database write context interleaving bug (#3822)

* UpdateIssueUsersByMentions was calling database write operations while
a transaction session was in progress. MailParticipants was failing
silently because of the SQLITE_LOCKED error. Make sure failures in
MailParticipants enter the log, and pass on the transaction context.

issue: let caller pass in database context, and use it
issue_comment: obtain database context to pass to UpdateIssueMentions
issue_comment: log any error from call to MailParticipants
issue_mail: pass on database context to UpdateIssueMentions

* issue: forgot debug statement

1 files changed, 5 insertions, 3 deletions

diff --git a/models/issue_comment.go b/models/issue_comment.go
index 091bfc3b..3f81889c 100644
--- a/models/issue_comment.go
+++ b/models/issue_comment.go
@@ -162,9 +162,9 @@ func (c *Comment) EventTag() string {
 
 // MailParticipants sends new comment emails to repository watchers
 // and mentioned people.
-func (cmt *Comment) MailParticipants(opType ActionType, issue *Issue) (err error) {
+func (cmt *Comment) MailParticipants(e Engine, opType ActionType, issue *Issue) (err error) {
 	mentions := markdown.FindAllMentions(cmt.Content)
-	if err = UpdateIssueMentions(cmt.IssueID, mentions); err != nil {
+	if err = UpdateIssueMentions(e, cmt.IssueID, mentions); err != nil {
 		return fmt.Errorf("UpdateIssueMentions [%d]: %v", cmt.IssueID, err)
 	}
 
@@ -278,7 +278,9 @@ func createComment(e *xorm.Session, opts *CreateCommentOptions) (_ *Comment, err
 		if err = notifyWatchers(e, act); err != nil {
 			log.Error(4, "notifyWatchers: %v", err)
 		}
-		comment.MailParticipants(act.OpType, opts.Issue)
+		if err = comment.MailParticipants(e, act.OpType, opts.Issue); err != nil {
+			log.Error(4, "MailParticipants: %v", err)
+		}
 	}
 
 	return comment, comment.loadAttributes(e)