From 1be367f87b22ae4f43e68dd3ef600e1ee4b30c44 Mon Sep 17 00:00:00 2001
From: "Jason A. Dönerfield" <no-replay@sl0p.foo>
Date: Sat, 18 Jul 2026 20:50:31 +0200
Subject: md2html: rewrite relative README links to the tree/ blob URL

The image-rewrite patch only fixed relative <img src>; relative <a href>
links (e.g. [docs/x.md](docs/x.md)) were still resolved by the browser
against the about/summary page URL, not the repo root, so they 404d.

Rewrite relative <a href> to absolute cgit URLs the same way:
  in-repo path -> /<repo>/tree/<path>?h=<branch>
  ../sibling   -> resolved against the repo URL location (/<sibling>)
Fragments are preserved; anchors, absolute, scheme and query-only URLs
are left untouched.
---
 filters/html-converters/md2html | 71 ++++++++++++++++++++++++++++++++++-------
 1 file changed, 60 insertions(+), 11 deletions(-)

(limited to 'filters')

diff --git a/filters/html-converters/md2html b/filters/html-converters/md2html
index faa71f3..90021a7 100755
--- a/filters/html-converters/md2html
+++ b/filters/html-converters/md2html
@@ -357,27 +357,76 @@ html = markdown.markdown(
 	extension_configs={
 		"markdown.extensions.codehilite":{"css_class":"highlight"}})
 
-# A README's relative image paths (e.g. screenshots/x.png) are repo blobs, which
-# cgit only serves via its `plain` command; but a browser resolves a relative
-# <img src> against the about-page URL (/<repo>/about/), so the image 404s.
-# Rewrite relative <img src> to an absolute /<repo>/plain/<path>?h=<branch> URL
-# (absolute so it also works where cgit renders the readme on the summary page).
+# A README's relative paths point at repo content, but a browser resolves them
+# against the page the readme is shown on (/<repo>/about/ or the summary page
+# /<repo>/), not against the repo root — so they 404. cgit serves blobs only via
+# its `plain`/`tree` commands, so rewrite relative references to absolute cgit
+# URLs (absolute so it works both on the about page and the summary page):
+#   <img src>   -> /<repo>/plain/<path>?h=<branch>   (raw bytes for the browser)
+#   <a href>    -> /<repo>/tree/<path>?h=<branch>     (browsable file/dir view)
+# Relative hrefs are resolved as paths against the repo root; a href that climbs
+# out of the repo with ".." (e.g. ../sibling) is resolved against the repo's URL
+# location instead (-> /sibling), matching how sibling repos are addressed.
 # cgit exports the repo context to about-filters via these environment vars; if
-# they're absent we leave the src untouched.
+# they're absent we leave the references untouched.
 import os, re
+from urllib.parse import urljoin
 repo = os.environ.get("CGIT_REPO_URL", "").strip("/")
 if repo:
 	branch = os.environ.get("CGIT_REPO_DEFBRANCH", "").strip()
-	plain = "/" + repo + "/plain/"
+	repo_root = "/" + repo + "/"
+	plain = repo_root + "plain/"
 	query = ("?h=" + branch) if branch else ""
-	# leave absolute, protocol-relative, root-relative, anchor and data: URLs alone
-	skip = re.compile(r"^(?:[a-z][a-z0-9+.\-]*:|//|/|#)", re.I)
-	def rewrite(m):
+	# leave absolute, protocol-relative, root-relative, anchor, query-only and
+	# scheme (mailto:, http:, data:, ...) URLs alone
+	skip = re.compile(r"^(?:[a-z][a-z0-9+.\-]*:|//|/|[#?])", re.I)
+
+	def rewrite_img(m):
 		url = m.group(2)
 		if not url or skip.match(url):
 			return m.group(0)
 		return m.group(1) + plain + re.sub(r"^\./", "", url) + query + m.group(3)
-	html = re.sub(r'(<img\b[^>]*?\bsrc=")([^"]*)(")', rewrite, html, flags=re.I)
+
+	def _split_frag(url):
+		# split off a trailing #fragment (kept verbatim on the rewritten URL)
+		if "#" in url:
+			path, frag = url.split("#", 1)
+			return path, "#" + frag
+		return url, ""
+
+	def _normalize(path):
+		# resolve "." / ".." against the repo root; returns (climbs, cleaned)
+		# where `climbs` counts ".." segments that escaped above the repo root.
+		out, climbs = [], 0
+		for seg in path.split("/"):
+			if seg in ("", "."):
+				continue
+			if seg == "..":
+				if out:
+					out.pop()
+				else:
+					climbs += 1
+			else:
+				out.append(seg)
+		return climbs, "/".join(out)
+
+	def rewrite_href(m):
+		url = m.group(2)
+		if not url or skip.match(url):
+			return m.group(0)
+		path, frag = _split_frag(url)
+		climbs, cleaned = _normalize(path)
+		if climbs:
+			# escapes the repo (sibling repo etc.): resolve against repo location
+			dest = urljoin(repo_root, "../" * climbs + cleaned)
+		elif cleaned:
+			dest = repo_root + "tree/" + cleaned + query
+		else:
+			dest = repo_root + (query or "")
+		return m.group(1) + dest + frag + m.group(3)
+
+	html = re.sub(r'(<img\b[^>]*?\bsrc=")([^"]*)(")', rewrite_img, html, flags=re.I)
+	html = re.sub(r'(<a\b[^>]*?\bhref=")([^"]*)(")', rewrite_href, html, flags=re.I)
 
 sys.stdout.write("<div class='markdown-body'>")
 sys.stdout.write(html)
-- 
cgit v1.3.1-sl0p