feat(releasepr): release PRs can be updated

- PR Description
- Read prefix+suffix from PR description and put into changelog
- Keep those overrides on PR description changes
- Add pending level to new PRs

internal/markdown/extensions/section.go

@@ -0,0 +1,88 @@
+package extensions
+
+import (
+	"regexp"
+
+	"github.com/yuin/goldmark"
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+
+	"github.com/apricote/releaser-pleaser/internal/markdown/extensions/ast"
+)
+
+var sectionStartRegex = regexp.MustCompile(`^<!-- section-start (.+) -->`)
+var sectionEndRegex = regexp.MustCompile(`^<!-- section-end (.+) -->`)
+
+const (
+	sectionTrigger     = "<!--"
+	SectionStartFormat = "<!-- section-start %s -->"
+	SectionEndFormat   = "<!-- section-end %s -->"
+)
+
+type sectionParser struct {
+}
+
+func (s *sectionParser) Open(_ gast.Node, reader text.Reader, _ parser.Context) (gast.Node, parser.State) {
+	line, _ := reader.PeekLine()
+
+	if result := sectionStartRegex.FindSubmatch(line); result != nil {
+		reader.AdvanceLine()
+		return ast.NewSection(string(result[1])), parser.HasChildren
+	}
+
+	return nil, parser.NoChildren
+}
+
+func (s *sectionParser) Continue(node gast.Node, reader text.Reader, _ parser.Context) parser.State {
+	n := node.(*ast.Section)
+
+	line, _ := reader.PeekLine()
+
+	if result := sectionEndRegex.FindSubmatch(line); result != nil {
+		if string(result[1]) == n.Name {
+			reader.AdvanceLine()
+			return parser.Close
+		}
+	}
+
+	return parser.Continue | parser.HasChildren
+}
+
+func (s *sectionParser) Close(_ gast.Node, _ text.Reader, _ parser.Context) {
+	// Nothing to do
+}
+
+func (s *sectionParser) CanInterruptParagraph() bool {
+	return true
+}
+
+func (s *sectionParser) CanAcceptIndentedLine() bool {
+	return false
+}
+
+var defaultSectionParser = &sectionParser{}
+
+// NewSectionParser returns a new BlockParser that can parse
+// a section block. Section blocks can be used to group various nodes under a parent ast node.
+// This parser must take precedence over the parser.HTMLParser.
+func NewSectionParser() parser.BlockParser {
+	return defaultSectionParser
+}
+
+func (s *sectionParser) Trigger() []byte {
+	return []byte(sectionTrigger)
+}
+
+type section struct {
+}
+
+// Section is an extension that allow you to use group content under a shared parent ast node.
+var Section = &section{}
+
+func (e *section) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithBlockParsers(
+		util.Prioritized(NewSectionParser(), 0),
+	))
+}