Fix ref links in issue overviews for tags (#8742)

* Properly generate ref URLs

Tags used to not generate correct URLs (src/branch/tags/1.0.0 instead of
src/tags/1.0.0).

Also cleans up some code around it with the created helper functions.

* Fix formatting and create migration

* Add copyright head to utils_test

* Use a raw query for the ref migration

* Remove semicolon

* Quote column and table names in migration SQL

* Change || to CONCAT, since MSSQL does not support ||

* Make migration engine aware

* Add missing import

* Move ref EndName and URL to the issue service

* Fix tests

* Add test for commit refs

* Update issue.go

* Use the right command for building JavaScript bundles

* Prepare for merge

* Check for refs/* before prepending in migration

* Update services/issue/issue_test.go

* Update modules/git/utils_test.go

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: techknowlogick <matti@mdranta.net>

modules/git/utils_test.go

@@ -0,0 +1,31 @@
+// Copyright 2020 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 git
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRefEndName(t *testing.T) {
+	// Test branch names (with and without slash).
+	assert.Equal(t, "foo", RefEndName("refs/heads/foo"))
+	assert.Equal(t, "feature/foo", RefEndName("refs/heads/feature/foo"))
+
+	// Test tag names (with and without slash).
+	assert.Equal(t, "foo", RefEndName("refs/tags/foo"))
+	assert.Equal(t, "release/foo", RefEndName("refs/tags/release/foo"))
+
+	// Test commit hashes.
+	assert.Equal(t, "c0ffee", RefEndName("c0ffee"))
+}
+
+func TestRefURL(t *testing.T) {
+	repoURL := "/user/repo"
+	assert.Equal(t, repoURL+"/src/branch/foo", RefURL(repoURL, "refs/heads/foo"))
+	assert.Equal(t, repoURL+"/src/tag/foo", RefURL(repoURL, "refs/tags/foo"))
+	assert.Equal(t, repoURL+"/src/commit/c0ffee", RefURL(repoURL, "c0ffee"))
+}