7 files changed, 122 insertions, 43 deletions
diff --git a/MANUAL.txt b/MANUAL.txt
index 9f6c6f1..6ea6266 100644
--- a/MANUAL.txt
+++ b/MANUAL.txt
@@ -19,12 +19,13 @@ Global settings
 about-filter::
 	Specifies a command which will be invoked to format the content of about
 	pages (both top-level and for each repository). The command will get the
-	content of the about-file on its stdin, the name of the file as the
-	first argument, and the stdout from the command will be included
-	verbatim on the about page. Default value: none. When no about-filter is
-	set, the readme is escaped and served as plain text. A bundled Lua
-	filter, about-render.lua, renders markdown, man pages and plain text
-	when about-filter points at it. See also: "Filter API".
+	content of the about-file on its stdin and the name of the file, with
+	the tree url its links resolve against, as arguments, and the stdout
+	from the command will be included verbatim on the about page. Default
+	value: none. When no about-filter is set, the readme is escaped and
+	served as plain text. A bundled Lua filter, about-render.lua, renders
+	markdown, man pages and plain text when about-filter points at it. See
+	also: "Filter API".
 
 age-file::
 	Specifies a path, relative to each repository path, which can be used to
@@ -794,11 +795,16 @@ specification with one of these strings.
 Parameters are provided to filters as follows.
 
 about filter::
-	This filter is given a single parameter, the filename of the source file
-	to filter. The filter can use the filename to determine (for example)
-	the type of syntax to follow when formatting the readme file. The about
-	text that is to be filtered is available on standard input and the
-	filtered text is expected on standard output.
+	This filter is given three parameters. The first is the filename of the
+	source file to filter, which the filter can use to determine (for
+	example) the type of syntax to follow when formatting the readme file.
+	For a readme tracked in the repository, the second is the url of the
+	repository's tree page at the ref the readme was read from, ending in a
+	slash so a path in the tree can follow it, and the third is the query
+	that has to come after such a path, empty for the default branch. Both
+	are escaped for a url, and both are empty for a readme on disk and for
+	the site readme. The about text that is to be filtered is available on
+	standard input and the filtered text is expected on standard output.
 
 auth filter::
 	The authentication filter receives 12 parameters, in this order.
diff --git a/source/filter.c b/source/filter.c
index 5f96cc0..ec48007 100644
--- a/source/filter.c
+++ b/source/filter.c
@@ -498,8 +498,10 @@ struct cgit_filter *cgit_new_filter(const char *cmd, filter_type filtertype)
 	case TRAILER:
 		argument_count = 2;
 		break;
-	case SOURCE:
 	case ABOUT:
+		argument_count = 3;
+		break;
+	case SOURCE:
 		argument_count = 1;
 		break;
 	case COMMIT:
diff --git a/source/ui-repolist.c b/source/ui-repolist.c
index daf18f5..1c081c7 100644
--- a/source/ui-repolist.c
+++ b/source/ui-repolist.c
@@ -463,7 +463,7 @@ void cgit_print_site_readme(void)
 	cgit_print_layout_start();
 	if (!ctx.cfg.root_readme)
 		goto done;
-	cgit_open_filter(ctx.cfg.about_filter, ctx.cfg.root_readme);
+	cgit_open_filter(ctx.cfg.about_filter, ctx.cfg.root_readme, "", "");
 	html_include(ctx.cfg.root_readme);
 	cgit_close_filter(ctx.cfg.about_filter);
 done:
diff --git a/source/ui-shared.c b/source/ui-shared.c
index fd9cd20..94a749e 100644
--- a/source/ui-shared.c
+++ b/source/ui-shared.c
@@ -138,6 +138,47 @@ static void site_link(const char *page, const char *name, const char *title,
 }
 
 /*
+ * Write the url naming the repository, the page and the path, and return
+ * whether the url has opened its query string already.
+ */
+static int write_page_url(const char *page, const char *path)
+{
+	if (ctx.cfg.virtual_root) {
+		html_url_path(ctx.cfg.virtual_root);
+		html_url_path(ctx.repo->url);
+		if (ctx.repo->url[strlen(ctx.repo->url) - 1] != '/')
+			html("/");
+		if (page) {
+			html_url_path(page);
+			html("/");
+			if (path)
+				html_url_path(path);
+		}
+		return 0;
+	}
+	html_url_path(ctx.cfg.script_name);
+	html("?url=");
+	html_url_arg(ctx.repo->url);
+	if (ctx.repo->url[strlen(ctx.repo->url) - 1] != '/')
+		html("/");
+	if (page) {
+		html_url_arg(page);
+		html("/");
+		if (path)
+			html_url_arg(path);
+	}
+	return 1;
+}
+
+/*
+ * Whether head needs naming in a url, which the default branch does not.
+ */
+static int head_is_named(const char *head)
+{
+	return head && ctx.repo->defbranch && strcmp(head, ctx.repo->defbranch);
+}
+
+/*
  * Open an anchor and write the part of its href naming the repository, the
  * page and the path, leaving the href quote open for the caller to add its own
  * arguments and close. The return is the delimiter to put before the first of
@@ -146,7 +187,7 @@ static void site_link(const char *page, const char *name, const char *title,
 static const char *repolink(const char *title, const char *class, const char *page,
 	const char *head, const char *path)
 {
-	const char *delim = "?";
+	const char *delim;
 
 	html("<a");
 	if (title) {
@@ -156,32 +197,8 @@ static const char *repolink(const char *title, const char *class, const char *pa
 	}
 	link_class(class);
 	html(" href='");
-	if (ctx.cfg.virtual_root) {
-		html_url_path(ctx.cfg.virtual_root);
-		html_url_path(ctx.repo->url);
-		if (ctx.repo->url[strlen(ctx.repo->url) - 1] != '/')
-			html("/");
-		if (page) {
-			html_url_path(page);
-			html("/");
-			if (path)
-				html_url_path(path);
-		}
-	} else {
-		html_url_path(ctx.cfg.script_name);
-		html("?url=");
-		html_url_arg(ctx.repo->url);
-		if (ctx.repo->url[strlen(ctx.repo->url) - 1] != '/')
-			html("/");
-		if (page) {
-			html_url_arg(page);
-			html("/");
-			if (path)
-				html_url_arg(path);
-		}
-		delim = "&amp;";
-	}
-	if (head && ctx.repo->defbranch && strcmp(head, ctx.repo->defbranch)) {
+	delim = write_page_url(page, path) ? "&amp;" : "?";
+	if (head_is_named(head)) {
 		html(delim);
 		html("h=");
 		html_url_arg(head);
@@ -911,6 +928,22 @@ char *cgit_pageurl(const char *reponame, const char *pagename, const char *query
 	return cgit_fileurl(reponame, pagename, NULL, query);
 }
 
+void cgit_tree_url(const char *head, struct strbuf *base, struct strbuf *query)
+{
+	int query_open;
+
+	html_capture_begin(base);
+	query_open = write_page_url("tree", NULL);
+	html_capture_end();
+	if (!head_is_named(head))
+		return;
+	html_capture_begin(query);
+	html(query_open ? "&" : "?");
+	html("h=");
+	html_url_arg(head);
+	html_capture_end();
+}
+
 const char *cgit_snapshot_prefix(const struct cgit_repo *repo)
 {
 	if (repo->snapshot_prefix)
diff --git a/source/ui-shared.h b/source/ui-shared.h
index 93cc9d2..dd90196 100644
--- a/source/ui-shared.h
+++ b/source/ui-shared.h
@@ -32,6 +32,14 @@ extern char *cgit_fileurl(const char *reponame, const char *pagename, const char
 extern char *cgit_pageurl(const char *reponame, const char *pagename, const char *query);
 
 /*
+ * The url of the current repository's tree page at head, split where a path
+ * in the tree goes, for a filter to build links of its own from. Both parts
+ * are escaped for a url but not for HTML, and query stays empty for the
+ * default branch.
+ */
+extern void cgit_tree_url(const char *head, struct strbuf *base, struct strbuf *query);
+
+/*
  * Call fn once for every URL this repository can be cloned from.
  */
 extern void cgit_add_clone_urls(void (*fn)(const char *));
diff --git a/source/ui-summary.c b/source/ui-summary.c
index e7b229a..44abc6b 100644
--- a/source/ui-summary.c
+++ b/source/ui-summary.c
@@ -91,14 +91,22 @@ void cgit_print_repo_readme(void)
 		}
 		html("</pre>");
 	} else {
+		struct strbuf tree_base = STRBUF_INIT, tree_query = STRBUF_INIT;
+
+		// A tracked readme's links lead into the tree at the ref it was
+		// read from, while one on disk has no tree to lead into.
+		if (ref)
+			cgit_tree_url(ref, &tree_base, &tree_query);
 		// The filter is what makes the source safe here, so it is fed
 		// through unescaped.
-		cgit_open_filter(ctx.repo->about_filter, filename);
+		cgit_open_filter(ctx.repo->about_filter, filename, tree_base.buf, tree_query.buf);
 		if (ref)
 			cgit_print_file(filename, ref, 1, 0);
 		else
 			html_include(filename);
 		cgit_close_filter(ctx.repo->about_filter);
+		strbuf_release(&tree_base);
+		strbuf_release(&tree_query);
 	}
 	html("</div>");
 	cgit_print_layout_end();
diff --git a/tests/t0201-filters.sh b/tests/t0201-filters.sh
index 11fa5f8..c6b23af 100755
--- a/tests/t0201-filters.sh
+++ b/tests/t0201-filters.sh
@@ -30,7 +30,7 @@ do
 	"
 
 	test_expect_success "check whether the $prefix about filter works" '
-		grep "<div id='"'"'about'"'"'>a+b HELLO$" tmp
+		grep "<div id='"'"'about'"'"'>a+b /filter-$prefix/tree/  HELLO$" tmp
 	'
 
 	test_expect_success "generate filter-$prefix/commit/" "
@@ -61,10 +61,32 @@ do
 
 	test_expect_success "the $prefix about filter output stays inside its div" "
 		cgit_url 'filter-$prefix/about/' >tmp &&
-		grep \"<div id='about'>a+b HELLO\" tmp
+		grep \"<div id='about'>a+b /filter-$prefix/tree/  HELLO\" tmp
 	"
 done
 
+# A readme read at another branch links into the tree at that branch, which
+# the filter is told as the query to follow a path with.
+test_expect_success 'the about filter gets the tree url at the readme branch' '
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "readme=:a+b" &&
+		echo "about-filter=exec:$FILTER_DIRECTORY/dump.sh" &&
+		echo "root-readme=$PWD/root.txt" &&
+		echo "repo.url=filtered" &&
+		echo "repo.path=$PWD/repos/filter/.git"
+	} >aboutargsrc &&
+	CGIT_CONFIG="$PWD/aboutargsrc" QUERY_STRING="url=filtered/about/&h=1%2b2" cgit >tmp &&
+	grep "<div id=.about.>a+b /filtered/tree/ ?h=1%2B2 HELLO" tmp
+'
+
+test_expect_success 'the site readme leaves the tree url empty' '
+	echo site >root.txt &&
+	CGIT_CONFIG="$PWD/aboutargsrc" QUERY_STRING="p=about" cgit >tmp &&
+	grep "root.txt   SITE" tmp
+'
+
 test "$CGIT_HAS_LUA" -eq 1 && test_set_prereq CGIT_LUA
 test "$CGIT_HAS_LUA" -eq 1 || say 'cgit built without lua, error page check skipped'