Refactor markup package (#32399)

To make the markup package easier to maintain:
1. Split some go files into small files
2. Use a shared util.NopCloser, remove duplicate code
3. Remove unused functions

modules/markup/render_links.go

@@ -0,0 +1,56 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markup
+
+import (
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type Links struct {
+	AbsolutePrefix bool   // add absolute URL prefix to auto-resolved links like "#issue", but not for pre-provided links and medias
+	Base           string // base prefix for pre-provided links and medias (images, videos)
+	BranchPath     string // actually it is the ref path, eg: "branch/features/feat-12", "tag/v1.0"
+	TreePath       string // the dir of the file, eg: "doc" if the file "doc/CHANGE.md" is being rendered
+}
+
+func (l *Links) Prefix() string {
+	if l.AbsolutePrefix {
+		return setting.AppURL
+	}
+	return setting.AppSubURL
+}
+
+func (l *Links) HasBranchInfo() bool {
+	return l.BranchPath != ""
+}
+
+func (l *Links) SrcLink() string {
+	return util.URLJoin(l.Base, "src", l.BranchPath, l.TreePath)
+}
+
+func (l *Links) MediaLink() string {
+	return util.URLJoin(l.Base, "media", l.BranchPath, l.TreePath)
+}
+
+func (l *Links) RawLink() string {
+	return util.URLJoin(l.Base, "raw", l.BranchPath, l.TreePath)
+}
+
+func (l *Links) WikiLink() string {
+	return util.URLJoin(l.Base, "wiki")
+}
+
+func (l *Links) WikiRawLink() string {
+	return util.URLJoin(l.Base, "wiki/raw")
+}
+
+func (l *Links) ResolveMediaLink(isWiki bool) string {
+	if isWiki {
+		return l.WikiRawLink()
+	} else if l.HasBranchInfo() {
+		return l.MediaLink()
+	}
+	return l.Base
+}