feat: render org-mode file links with line numbers (#12496)

This change renders file links in org-mode like `./module.el::20` as a link to the 20th
line, for example. It also strips off other search types that are not currently supported
in forgejo like regex search to avoid generating invalid URLs.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12496
Reviewed-by: Gusted <gusted@noreply.codeberg.org>

modules/markup/orgmode/orgmode.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"html"
 	"io"
+	"strconv"
 	"strings"
 
 	"forgejo.org/modules/highlight"
@@ -159,6 +160,16 @@ func (r *Writer) resolveLink(node org.Node) string {
 		switch l.Kind() {
 		case "image", "video":
 			base = r.Ctx.Links.ResolveMediaLink(r.Ctx.IsWiki)
+		case "regular":
+			// Convert line search syntax to line links
+			target, search, found := strings.Cut(link, "::")
+			if found {
+				if _, err := strconv.Atoi(search); err == nil {
+					link = target + "#L" + search
+				} else {
+					link = target
+				}
+			}
 		}
 
 		link = util.URLJoin(base, link)

modules/markup/orgmode/orgmode_test.go

@@ -89,6 +89,43 @@ func TestRender_BaseLinks(t *testing.T) {
 		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/deep/nested/folder/src">./src/</a></p>`)
 }
 
+func TestRender_SearchSuffix(t *testing.T) {
+	setting.AppURL = AppURL
+	setting.AppSubURL = AppSubURL
+
+	test := func(input, expected string) {
+		buffer, err := RenderString(&markup.RenderContext{
+			Ctx: git.DefaultContext,
+			Links: markup.Links{
+				Base:       setting.AppSubURL,
+				BranchPath: "branch/main",
+			},
+		}, input)
+		require.NoError(t, err)
+		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
+	}
+
+	// `::N` line search becomes an `#L<n>` anchor.
+	test("[[./file.el::35][line 35]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.el#L35">line 35</a></p>`)
+	test("[[file:./file.el::35][line 35]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.el#L35">line 35</a></p>`)
+
+	// Other search types are ignored.
+	test("[[./file.org::*Heading][heading]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.org">heading</a></p>`)
+	test("[[./file.org::#custom-id][heading]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.org">heading</a></p>`)
+	test("[[./file.el::/regex/][regex]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.el">regex</a></p>`)
+	test("[[file:./file.el::][no search]]",
+		`<p><a href="http://localhost:3000/gogits/gogs/src/branch/main/file.el">no search</a></p>`)
+
+	// Absolute URLs that happen to contain `::` are unchanged.
+	test("[[https://example.com/foo::35][ext]]",
+		`<p><a href="https://example.com/foo::35">ext</a></p>`)
+}
+
 func TestRender_Media(t *testing.T) {
 	setting.AppURL = AppURL
 	setting.AppSubURL = AppSubURL