auto* sub = app.add_subcommand("add", "Add file contents to the index");
sub->add_option("<files>", m_add_files, "Files to add content from.");
sub->add_flag(
"-A,--all,--no-ignore-removal",
m_all_flag,
"Update the index not only where the working tree has a file matching <pathspec> but also where the index already has an entry. This adds, modifies, and removes index entries to match the working tree.\n\nIf no <pathspec> is given when -A option is used, all files in the entire working tree are updated (old versions of Git used to limit the update to the current directory and its subdirectories)."