directory_lister: add ctor with opened directory

This ctor allows the caller to open the directory first,
on its own, and pass it down to the directory_lister.

Once all callers use this ctor we can get rid of
the delayed open in the get() method.

Also, in can be used to replace full-path based file_stat calls
on listed entries with file_stat(directory, name) calls
that are based on statat() and a relative path name that is present
in the listed directory entry.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

sq

utils/lister.hh

@@ -196,6 +196,18 @@ public:
         , _do_show_hidden(do_show_hidden)
     { }
 
+    directory_lister(file opened_directory, fs::path dir,
+            lister::dir_entry_types type = lister::dir_entry_types::full(),
+            lister::filter_type filter = [] (const fs::path& parent_dir, const directory_entry& entry) { return true; },
+            lister::show_hidden do_show_hidden = lister::show_hidden::yes) noexcept
+        : _dir(std::move(dir))
+        , _type(type)
+        , _filter(std::move(filter))
+        , _do_show_hidden(do_show_hidden)
+        , _opened(std::move(opened_directory))
+        , _gen(_opened.experimental_list_directory())
+    { }
+
     directory_lister(directory_lister&&) noexcept = default;
 
     ~directory_lister();