Add html_include()

This is a function used to include external htmlfiles in cgit-
generated pages.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

cgit.h

@@ -144,6 +144,7 @@ extern void html_hidden(char *name, char *value);
 extern void html_link_open(char *url, char *title, char *class);
 extern void html_link_close(void);
 extern void html_filemode(unsigned short mode);
+extern int html_include(const char *filename);
 
 extern int cgit_read_config(const char *filename, configfn fn);
 extern int cgit_parse_query(char *txt, configfn fn);

html.c

@@ -166,3 +166,17 @@ void html_filemode(unsigned short mode)
 	html_fileperm(mode >> 3);
 	html_fileperm(mode);
 }
+
+int html_include(const char *filename)
+{
+	FILE *f;
+	char buf[4096];
+	size_t len;
+
+	if (!(f = fopen(filename, "r")))
+		return -1;
+	while((len = fread(buf, 1, 4096, f)) > 0)
+		write(htmlfd, buf, len);
+	fclose(f);
+	return 0;
+}