Remove troublesome chars from cachefile names

Add a funtion cache_safe_filename() which replaces possibly bad filename
characters with '_'.

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

cache.c

@@ -10,6 +10,22 @@
 
 const int NOLOCK = -1;
 
+char *cache_safe_filename(const char *unsafe)
+{
+	static char buf[PATH_MAX];
+	char *s = buf;
+	char c;
+
+	while(unsafe && (c = *unsafe++) != 0) {
+		if (c == '/' || c == ' ' || c == '&' || c == '|' || 
+		    c == '>' || c == '<' || c == '.')
+			c = '_';
+		*s++ = c;
+	}
+	*s = '\0';
+	return buf;
+}
+
 int cache_exist(struct cacheitem *item)
 {
 	if (stat(item->name, &item->st)) {

cgit.c

@@ -22,7 +22,7 @@ static void cgit_prepare_cache(struct cacheitem *item)
 	} else {
 		item->name = xstrdup(fmt("%s/%s/%s/%s.html", cgit_cache_root, 
 			   cgit_query_repo, cgit_query_page, 
-			   cgit_querystring));
+			   cache_safe_filename(cgit_querystring)));
 		if (cgit_query_has_symref)
 			item->ttl = cgit_cache_dynamic_ttl;
 		else if (cgit_query_has_sha1)

cgit.h

@@ -87,6 +87,7 @@ extern int cgit_read_config(const char *filename, configfn fn);
 extern int cgit_parse_query(char *txt, configfn fn);
 extern struct commitinfo *cgit_parse_commit(struct commit *commit);
 
+extern char *cache_safe_filename(const char *unsafe);
 extern int cache_lock(struct cacheitem *item);
 extern int cache_unlock(struct cacheitem *item);
 extern int cache_cancel_lock(struct cacheitem *item);