Ignore issue template with a special name (#21830)

A file in `ISSUE_TEMPLATE` with the name `config.yml` shouldn't be
treated as a YAML template, it's for [configuring the template
chooser](https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#configuring-the-template-chooser).

The old code tried to ignore the file, but it didn't work, caused by
#20987. That's why the warning is displayed:

<img width="415" alt="image"
src="https://user-images.githubusercontent.com/9418365/202094067-804c42fe-0e9e-4fc5-bf01-d95fa336f54f.png">

Note that this PR is not an implementation of `config.yml`, there will
be another one to do it.

1 files changed, 43 insertions, 0 deletions

diff --git a/modules/structs/issue_test.go b/modules/structs/issue_test.go
new file mode 100644
index 0000000000..5312585d0f
--- /dev/null
+++ b/modules/structs/issue_test.go
@@ -0,0 +1,43 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package structs
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIssueTemplate_Type(t *testing.T) {
+	tests := []struct {
+		fileName string
+		want     IssueTemplateType
+	}{
+		{
+			fileName: ".gitea/ISSUE_TEMPLATE/bug_report.yaml",
+			want:     IssueTemplateTypeYaml,
+		},
+		{
+			fileName: ".gitea/ISSUE_TEMPLATE/bug_report.md",
+			want:     IssueTemplateTypeMarkdown,
+		},
+		{
+			fileName: ".gitea/ISSUE_TEMPLATE/bug_report.txt",
+			want:     "",
+		},
+		{
+			fileName: ".gitea/ISSUE_TEMPLATE/config.yaml",
+			want:     "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.fileName, func(t *testing.T) {
+			it := IssueTemplate{
+				FileName: tt.fileName,
+			}
+			assert.Equal(t, tt.want, it.Type())
+		})
+	}
+}