Large refactor. Use rayon, 10X performance boost

Code changes:
Removed ignore & channel crates. Using a single reciever thread to build
a hashmap to prevend duplicate inodes being reported gave a severe
performance penalty

Using rayon crate with some hand crafted file traversal has improved
performance aprox 10X

Behaviour changes:

Removed parameter 'limit by filesystem' - don't think this is used, and
I only added it as it was easy to add with the ignore crate.

Sym links will now not appear in the output tree unless using '-s'
'apparent-size' flag

Change behaviour of multiple args so that it unifies them and
compares them under one tree instead of treating them
individually: https://github.com/bootandy/dust/issues/136

tests/test_exact_output.rs

@@ -114,8 +114,6 @@ pub fn test_main_long_paths() {
         .unwrap()
         .stdout;
     let output = str::from_utf8(&assert).unwrap();
-    println!("{:?}", output.trim());
-    println!("{:?}", main_output_long_paths().trim());
     assert!(output.contains(&main_output_long_paths()));
 }
 
@@ -204,9 +202,9 @@ fn no_substring_of_names_output() -> String {
    0B   ┌── long_dir_name_what_a_very_long_dir_name_what_happens_when_this_g..
  4.0K   ├── dir_name_clash
  4.0K   │ ┌── hello
- 8.0K   ├─┴ dir_substring
- 4.0K   │ ┌── hello
  8.0K   ├─┴ dir
+ 4.0K   │ ┌── hello
+ 8.0K   ├─┴ dir_substring
   24K ┌─┴ test_dir2
     "
     .trim()
@@ -218,10 +216,10 @@ fn no_substring_of_names_output() -> String {
     "
    0B   ┌── long_dir_name_what_a_very_long_dir_name_what_happens_when_this_g..
  4.0K   │ ┌── hello
- 4.0K   ├─┴ dir_substring
+ 4.0K   ├─┴ dir
  4.0K   ├── dir_name_clash
  4.0K   │ ┌── hello
- 4.0K   ├─┴ dir
+ 4.0K   ├─┴ dir_substring
   12K ┌─┴ test_dir2
   "
     .trim()
@@ -247,8 +245,8 @@ pub fn test_unicode_directories() {
 fn unicode_dir() -> String {
     // The way unicode & asian characters are rendered on the terminal should make this line up
     "
-   0B   ┌── 👩.unicode                │                                 █ │   0%
-   0B   ├── ラウトは難しいです！.japan│                                 █ │   0%
+   0B   ┌── ラウトは難しいです！.japan│                                 █ │   0%
+   0B   ├── 👩.unicode                │                                 █ │   0%
  4.0K ┌─┴ test_dir_unicode            │██████████████████████████████████ │ 100%
     "
     .trim()
@@ -258,8 +256,8 @@ fn unicode_dir() -> String {
 #[cfg(target_os = "macos")]
 fn unicode_dir() -> String {
     "
-   0B   ┌── 👩.unicode                │                                 █ │   0%
-   0B   ├── ラウトは難しいです！.japan│                                 █ │   0%
+   0B   ┌── ラウトは難しいです！.japan│                                 █ │   0%
+   0B   ├── 👩.unicode                │                                 █ │   0%
    0B ┌─┴ test_dir_unicode            │                                 █ │   0%
     "
     .trim()

tests/test_flags.rs

@@ -142,8 +142,8 @@ pub fn test_number_of_files() {
         .unwrap()
         .stdout;
     let output = str::from_utf8(&output).unwrap();
-    assert!(output.contains("1     ┌── hello_file"));
-    assert!(output.contains("1     ├── a_file "));
+    assert!(output.contains("1     ┌── a_file "));
+    assert!(output.contains("1     ├── hello_file"));
     assert!(output.contains("3   ┌─┴ many"));
     assert!(output.contains("4 ┌─┴ test_dir"));
 }

tests/tests_symlinks.rs

@@ -2,7 +2,6 @@ use assert_cmd::Command;
 use std::cmp::max;
 use std::fs::File;
 use std::io::Write;
-use std::panic;
 use std::path::PathBuf;
 use std::str;
 
@@ -61,12 +60,12 @@ pub fn test_soft_sym_link() {
         .output();
     assert!(c.is_ok());
 
-    let c = format!(" ┌── {}", get_file_name(link_name_s.into()));
-    let b = format!(" ├── {}", get_file_name(file_path_s.into()));
+    let c = format!(" ├── {}", get_file_name(link_name_s.into()));
+    let b = format!(" ┌── {}", get_file_name(file_path_s.into()));
     let a = format!("─┴ {}", dir_s);
 
     let mut cmd = Command::cargo_bin("dust").unwrap();
-    let output = cmd.arg("-p").arg("-c").arg(dir_s).unwrap().stdout;
+    let output = cmd.arg("-p").arg("-c").arg("-s").arg(dir_s).unwrap().stdout;
 
     let output = str::from_utf8(&output).unwrap();
 
@@ -125,9 +124,16 @@ pub fn test_recursive_sym_link() {
     let b = format!(" └── {}", get_file_name(link_name_s.into()));
 
     let mut cmd = Command::cargo_bin("dust").unwrap();
-    let output = cmd.arg("-p").arg("-c").arg("-r").arg(dir_s).unwrap().stdout;
-
+    let output = cmd
+        .arg("-p")
+        .arg("-c")
+        .arg("-r")
+        .arg("-s")
+        .arg(dir_s)
+        .unwrap()
+        .stdout;
     let output = str::from_utf8(&output).unwrap();
+
     assert!(output.contains(a.as_str()));
     assert!(output.contains(b.as_str()));
 }