Merge branch 'bw/forking-and-threading'

The "run-command" API implementation has been made more robust
against dead-locking in a threaded environment.

* bw/forking-and-threading:
  usage.c: drop set_error_handle()
  run-command: restrict PATH search to executable files
  run-command: expose is_executable function
  run-command: block signals between fork and execve
  run-command: add note about forking and threading
  run-command: handle dup2 and close errors in child
  run-command: eliminate calls to error handling functions in child
  run-command: don't die in child when duping /dev/null
  run-command: prepare child environment before forking
  string-list: add string_list_remove function
  run-command: use the async-signal-safe execv instead of execvp
  run-command: prepare command before forking
  t0061: run_command executes scripts without a #! line
  t5550: use write_script to generate post-update hook

string-list.c

@@ -64,6 +64,24 @@ struct string_list_item *string_list_insert(struct string_list *list, const char
 	return list->items + index;
 }
 
+void string_list_remove(struct string_list *list, const char *string,
+			int free_util)
+{
+	int exact_match;
+	int i = get_entry_index(list, string, &exact_match);
+
+	if (exact_match) {
+		if (list->strdup_strings)
+			free(list->items[i].string);
+		if (free_util)
+			free(list->items[i].util);
+
+		list->nr--;
+		memmove(list->items + i, list->items + i + 1,
+			(list->nr - i) * sizeof(struct string_list_item));
+	}
+}
+
 int string_list_has_string(const struct string_list *list, const char *string)
 {
 	int exact_match;