Do not show the "Sign up for free" button in issue tracker (#3408)

* Do not show the "Sign up for free" button in issue tracker

The "Sign in to comment" link is good enough and will correctly
show or not show the "Sign Up" button link for those not having
an account already.

Fixes #3407 (link to nowhere when registration is disabled)

* Move html from translation to template

* Remove extra space in `{{ .SignInLink }}`.

conf/locale/locale_en-US.ini

@@ -485,8 +485,7 @@ issues.commit_ref_at = `referenced this issue from a commit <a id="%[1]s" href="
 issues.poster = Poster
 issues.collaborator = Collaborator
 issues.owner = Owner
-issues.sign_up_for_free = Sign up for free
+issues.sign_in_require_desc = Sign in to comment
-issues.sign_in_require_desc = to join this conversation. Already have an account? <a href="%s">Sign in to comment</a>
 issues.edit = Edit
 issues.cancel = Cancel
 issues.save = Save

templates/repo/issue/view_content.tmpl

@@ -227,8 +227,7 @@
 				</div>
 			{{else}}
 				<div class="ui warning message">
-					<a href="{{AppSubUrl}}/user/sign_up" class="ui green button">{{.i18n.Tr "repo.issues.sign_up_for_free"}}</a>
+					<a href="{{.SignInLink}}">{{.i18n.Tr "repo.issues.sign_in_require_desc" | Safe}}</a>
-					{{.i18n.Tr "repo.issues.sign_in_require_desc" .SignInLink | Safe}}
 				</div>
 			{{end}}
 		</ui>