shell: added completion support

src/shell.c

@@ -1,5 +1,10 @@
 #include "shell.h"
 
+char** s_completion(const char* text, int start, int end) {
+  rl_attempted_completion_over = 1;
+  return rl_completion_matches(text, s_names);
+}
+
 void s_die(const char* msg) {
   fprintf(stderr, "s: %s\n", msg);
   exit(1);
@@ -72,6 +77,8 @@ int s_exec(char** args) {
 }
 
 void s_loop() {
+  rl_attempted_completion_function = s_completion;
+
   char** cmd;
   int s;