appview: render markdown in issues

appview/pages/funcmap.go

···
 			}
 			return v.Slice(start, end).Interface()
 		},
+		"markdown": func(text string) template.HTML {
+			return template.HTML(renderMarkdown(text))
+		},
 	}
 }

appview/pages/markdown.go

···
+package pages
+
+import (
+	"bytes"
+
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/extension"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer/html"
+)
+
+func renderMarkdown(source string) string {
+	md := goldmark.New(
+		goldmark.WithExtensions(extension.GFM),
+		goldmark.WithParserOptions(
+			parser.WithAutoHeadingID(),
+		),
+		goldmark.WithRendererOptions(
+			html.WithHardWraps(),
+			html.WithXHTML(),
+		),
+	)
+	var buf bytes.Buffer
+	if err := md.Convert([]byte(source), &buf); err != nil {
+		return source
+	}
+	return buf.String()
+}

appview/pages/templates/repo/issues/issue.html

···
 
         {{ if .Issue.Body }}
             <article id="body" class="mt-8">
-                {{ .Issue.Body | escapeHtml }}
+                {{ .Issue.Body | markdown }}
             </article>
         {{ end }}
     </section>
···
                     </a>
                 </div>
                 <div class="">
-                    {{ nl2br .Body }}
+                    {{ .Body | markdown }}
                 </div>
             </div>
         {{ end }}

go.mod

···
 	github.com/russross/blackfriday/v2 v2.1.0
 	github.com/sethvargo/go-envconfig v1.1.0
 	github.com/whyrusleeping/cbor-gen v0.2.1-0.20241030202151-b7a6831be65e
+	github.com/yuin/goldmark v1.4.13
 	golang.org/x/xerrors v0.0.0-20231012003039-104605ab7028
 )
 

go.sum

···
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
+github.com/yuin/goldmark v1.4.13 h1:fVcFKWvrslecOb/tg+Cc05dkeYx540o0FuFt3nUVDoE=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 gitlab.com/yawning/secp256k1-voi v0.0.0-20230925100816-f2616030848b h1:CzigHMRySiX3drau9C6Q5CAbNIApmLdat5jPMqChvDA=
 gitlab.com/yawning/secp256k1-voi v0.0.0-20230925100816-f2616030848b/go.mod h1:/y/V339mxv2sZmYYR64O07VuCpdNZqCTwO8ZcouTMI8=