Shell: Add "history" command that shows command history.

Shell/main.cpp

@@ -19,6 +19,7 @@
 //#define SH_DEBUG
 
 GlobalState g;
+static LineEditor editor;
 
 static void prompt()
 {
@@ -112,6 +113,14 @@ static int sh_cd(int argc, char** argv)
  return 0;
 }
 
+static int sh_history(int, char**)
+{
+ for (int i = 0; i < editor.history().size(); ++i) {
+ printf("%6d %s\n", i, editor.history()[i].characters());
+ }
+ return 0;
+}
+
 static bool handle_builtin(int argc, char** argv, int& retval)
 {
  if (argc == 0)
@@ -132,6 +141,10 @@ static bool handle_builtin(int argc, char** argv, int& retval)
  retval = sh_export(argc, argv);
  return true;
  }
+ if (!strcmp(argv[0], "history")) {
+ retval = sh_history(argc, argv);
+ return true;
+ }
  return false;
 }
 
@@ -387,7 +400,6 @@ int main(int argc, char** argv)
  free(cwd);
  }
 
- LineEditor editor;
  for (;;) {
  prompt();
  auto line = editor.get_line();