From 180ecdad0c0d9d2587c70ac893e881f7217a49e8 Mon Sep 17 00:00:00 2001
From: Bryce Kwon <bryce@brycekwon.com>
Date: Sun, 1 Nov 2026 17:21:33 -1000
Subject: Answer a submodule path with the submodule

The tree page read the gitlink's commit as a blob, which outside the
repository is a bad object id and inside it is the commit's raw text.
---
 source/ui-shared.c | 42 ++++++++++++++++++++++++++++++------------
 source/ui-shared.h |  6 ++++++
 source/ui-tree.c   |  9 +++++++--
 3 files changed, 43 insertions(+), 14 deletions(-)

(limited to 'source')

diff --git a/source/ui-shared.c b/source/ui-shared.c
index e346cbd..c3eee0b 100644
--- a/source/ui-shared.c
+++ b/source/ui-shared.c
@@ -1522,24 +1522,21 @@ static void print_docstart(void)
 		html_include(ctx.cfg.header);
 }
 
-void cgit_print_error_page(int code, const char *msg, const char *fmt, ...)
+/*
+ * Start the page an error is printed into, and answer whether it started.
+ * Once the status line is out the error can only join the body under way,
+ * and the page that hit it carries on to its own end.
+ */
+static int start_error_page(int code, const char *msg)
 {
-	va_list ap;
-
 	// An error page describes a condition that may not outlast the slot
 	// holding it. A request naming a commit not yet pushed would cache its
 	// 404 under the never-expiring static ttl and keep serving it after
 	// the push, so the error is rendered straight to the visitor instead.
 	html_flush();
 	cache_abandon_fill();
-	va_start(ap, fmt);
-	// Once the status line is out the error can only join the body under
-	// way, and the page that hit it carries on to its own end.
-	if (ctx.page.headers_sent) {
-		vprint_error(fmt, ap);
-		va_end(ap);
-		return;
-	}
+	if (ctx.page.headers_sent)
+		return 0;
 	ctx.page.status = code;
 	ctx.page.statusmsg = msg;
 	// The error stands where a page would name itself, ahead of the
@@ -1554,9 +1551,30 @@ void cgit_print_error_page(int code, const char *msg, const char *fmt, ...)
 	ctx.page.charset = PAGE_ENCODING;
 	ctx.page.filename = NULL;
 	cgit_print_layout_start();
+	return 1;
+}
+
+void cgit_print_error_page(int code, const char *msg, const char *fmt, ...)
+{
+	int started = start_error_page(code, msg);
+	va_list ap;
+
+	va_start(ap, fmt);
 	vprint_error(fmt, ap);
 	va_end(ap);
-	cgit_print_layout_end();
+	if (started)
+		cgit_print_layout_end();
+}
+
+void cgit_print_submodule_page(char *path, const char *rev)
+{
+	int started = start_error_page(404, "Not Found");
+
+	html("<div class='error'>This path is a submodule: ");
+	cgit_submodule_link("ls-mod", path, rev);
+	html("</div>\n");
+	if (started)
+		cgit_print_layout_end();
 }
 
 void cgit_print_blob_too_large(size_t size)
diff --git a/source/ui-shared.h b/source/ui-shared.h
index fa73c83..e52a3ae 100644
--- a/source/ui-shared.h
+++ b/source/ui-shared.h
@@ -142,6 +142,12 @@ extern void cgit_print_error_page(int code, const char *msg, const char *fmt, ..
  */
 extern void cgit_print_blob_too_large(size_t size);
 
+/*
+ * Answer with the 404 page for a path naming a submodule, whose commit rev
+ * lives in another repository, linking it the way a tree listing does.
+ */
+extern void cgit_print_submodule_page(char *path, const char *rev);
+
 /*
  * Resolve rev to the parsed commit it names, peeling a tag, with oid set to
  * what rev itself names. Returns NULL once the 404 page naming rev is out.
diff --git a/source/ui-tree.c b/source/ui-tree.c
index 63b8984..f1b995a 100644
--- a/source/ui-tree.c
+++ b/source/ui-tree.c
@@ -470,6 +470,11 @@ static int walk_tree(const struct object_id *oid, struct strbuf *base,
 			strbuf_release(&fullpath);
 			ls_head();
 			return READ_TREE_RECURSIVE;
+		} else if (S_ISGITLINK(mode)) {
+			cgit_print_submodule_page(fullpath.buf, oid_to_hex(oid));
+			walk->state = WALK_ERROR_SHOWN;
+			strbuf_release(&fullpath);
+			return 0;
 		} else {
 			bool shown = print_object(oid, mode, fullpath.buf, pathname, walk->rev);
 
@@ -524,6 +529,6 @@ void cgit_print_tree(const char *rev, char *path)
 	} else if (walk.state == WALK_LOOKING) {
 		cgit_print_error_page(404, "Not Found", "Path not found");
 	}
-	// WALK_ERROR_SHOWN is left alone, since the error page print_object
-	// put out is already complete.
+	// WALK_ERROR_SHOWN is left alone, since the error page the walk put
+	// out is already complete.
 }
-- 
cgit 2.12.1