Disable ref selection dropdown if you don't have permissions to use it (#17837)

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/web/repo/issue.go

@@ -955,7 +955,6 @@ func NewIssuePost(ctx *context.Context) {
 	ctx.Data["NewIssueChooseTemplate"] = len(ctx.IssueTemplatesFromDefaultBranch()) > 0
 	ctx.Data["RequireHighlightJS"] = true
 	ctx.Data["RequireSimpleMDE"] = true
-	ctx.Data["ReadOnly"] = false
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
 	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
 	upload.AddUploadContext(ctx, "comment")
@@ -1630,7 +1629,6 @@ func ViewIssue(ctx *context.Context) {
 	ctx.Data["Participants"] = participants
 	ctx.Data["NumParticipants"] = len(participants)
 	ctx.Data["Issue"] = issue
-	ctx.Data["ReadOnly"] = false
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/login?redirect_to=" + url.QueryEscape(ctx.Data["Link"].(string))
 	ctx.Data["IsIssuePoster"] = ctx.IsSigned && issue.IsPoster(ctx.User.ID)
 	ctx.Data["HasIssuesOrPullsWritePermission"] = ctx.Repo.CanWriteIssuesOrPulls(issue.IsPull)

templates/repo/issue/branch_selector_field.tmpl

@@ -5,10 +5,10 @@
 	{{$.CsrfTokenHtml}}
 </form>
 
-<div class="ui {{if .ReadOnly}}disabled{{end}} floating filter select-branch dropdown" data-no-results="{{.i18n.Tr "repo.pulls.no_results"}}">
+<div class="ui {{if not .HasIssuesOrPullsWritePermission}}disabled{{end}} floating filter select-branch dropdown" data-no-results="{{.i18n.Tr "repo.pulls.no_results"}}">
 	<div class="ui basic small button">
 		<span class="text branch-name">{{if .Issue.Ref}}{{$.RefEndName}}{{else}}{{.i18n.Tr "repo.issues.no_ref"}}{{end}}</span>
-		{{svg "octicon-triangle-down" 14 "dropdown icon"}}
+		{{if .HasIssuesOrPullsWritePermission}}{{svg "octicon-triangle-down" 14 "dropdown icon"}}{{end}}
 	</div>
 	<div class="menu">
 		<div class="ui icon search input">