Automatically clear stopwatch on merging a PR (#4327)

* Don't display buttons if there are no notices

* clear stopwatch on merging a PR

* remove redundant gt check

* use ctx.Flash as per @bkcsoft comment

* stop timer on closing issues/PRs too

* updated translation as per review

* redirect to login page after successfully activating account

* remove unrelated changes

* stop timer for issues that are closed via commits too..Not just the 'close' UI button

routers/repo/issue_stopwatch.go

@@ -17,6 +17,13 @@ func IssueStopwatch(c *context.Context) {
 	if c.Written() {
 		return
 	}
+
+	var showSuccessMessage bool
+
+	if !models.StopwatchExists(c.User.ID, issue.ID) {
+		showSuccessMessage = true
+	}
+
 	if !c.Repo.CanUseTimetracker(issue, c.User) {
 		c.NotFound("CanUseTimetracker", nil)
 		return
@@ -27,6 +34,10 @@ func IssueStopwatch(c *context.Context) {
 		return
 	}
 
+	if showSuccessMessage {
+		c.Flash.Success(c.Tr("repo.issues.tracker_auto_close"))
+	}
+
 	url := issue.HTMLURL()
 	c.Redirect(url, http.StatusSeeOther)
 }