[BUG] Render references to cross-repo issues with external issues

- If you have the external issue setting enabled, any reference would
have been rendered as an external issue, however this shouldn't be
happening to references that refer to issues in other repositories.
- Unit test added.

(cherry picked from commit 05e163aaf3)

modules/markup/html.go

@@ -880,7 +880,7 @@ func issueIndexPatternProcessor(ctx *RenderContext, node *html.Node) {
 
 		var link *html.Node
 		reftext := node.Data[ref.RefLocation.Start:ref.RefLocation.End]
-		if hasExtTrackFormat && !ref.IsPull {
+		if hasExtTrackFormat && !ref.IsPull && ref.Owner == "" {
 			ctx.Metas["index"] = ref.Issue
 
 			res, err := vars.Expand(ctx.Metas["format"], ctx.Metas)

modules/markup/html_internal_test.go

@@ -342,6 +342,22 @@ func TestRender_AutoLink(t *testing.T) {
 	test(tmp, "<a href=\""+tmp+"\" class=\"commit\"><code class=\"nohighlight\">d8a994ef24 (diff-2)</code></a>")
 }
 
+func TestRender_IssueIndexPatternRef(t *testing.T) {
+	setting.AppURL = TestAppURL
+
+	test := func(input, expected string) {
+		var buf strings.Builder
+		err := postProcess(&RenderContext{
+			Ctx:   git.DefaultContext,
+			Metas: numericMetas,
+		}, []processor{issueIndexPatternProcessor}, strings.NewReader(input), &buf)
+		require.NoError(t, err)
+		assert.Equal(t, expected, buf.String(), "input=%q", input)
+	}
+
+	test("alan-turin/Enigma-cryptanalysis#1", `<a href="/alan-turin/enigma-cryptanalysis/issues/1" class="ref-issue">alan-turin/Enigma-cryptanalysis#1</a>`)
+}
+
 func TestRender_FullIssueURLs(t *testing.T) {
 	setting.AppURL = TestAppURL