dirstate: make parents() faster.
This allows localrepository.status() to avoid reading all but the
first 40 bytes of the dirstate in the common case of running "hg
status".
% init
% setup
% delete an empty directory
empty_dir
Removing directory empty_dir
directory
r1
% delete an untracked directory
untracked_dir/untracked_file1
untracked_dir/untracked_file2
Removing file untracked_dir/untracked_file1
Removing file untracked_dir/untracked_file2
Removing directory untracked_dir
directory
r1
% delete an untracked file
untracked_file
Removing file untracked_file
directory
r1
% delete an untracked file in a tracked directory
directory/untracked_file
Removing file directory/untracked_file
directory
r1
% delete nested directories
untracked_directory/nested_directory
Removing directory untracked_directory/nested_directory
Removing directory untracked_directory
directory
r1
% delete nested directories from a subdir
untracked_directory/nested_directory
Removing directory untracked_directory/nested_directory
Removing directory untracked_directory
directory
r1
% delete only part of the tree
untracked_directory/nested_directory
Removing directory untracked_directory/nested_directory
Removing directory untracked_directory
directory
r1
directory/untracked_file
% delete ignored files
ignored
Removing file ignored
directory
r1
% abort with missing files until we support name mangling filesystems
refused to run
untracked_file still around
untracked_file
refused to run
untracked_file still around
Removing file untracked_file
directory
r1