du: give -h output the same precision as GNU coreutils

When printing the `du -h` output GNU coreutils does autoscale
the size, e.g.
```
$ truncate -s12M a
$ truncate -s8500 b
$ truncate -s133456345 c
$ truncate -s56990456345 d
$ du -h --apparent-size a b c d
12M	a
8,4K	b
128M	c
54G	d
```
Align our version to do the same by sharing the code with `ls`.

Closes: #6159

src/uu/du/Cargo.toml

@@ -19,7 +19,7 @@ chrono = { workspace = true }
 # For the --exclude & --exclude-from options
 glob = { workspace = true }
 clap = { workspace = true }
-uucore = { workspace = true }
+uucore = { workspace = true, features = ["format"] }
 
 [target.'cfg(target_os = "windows")'.dependencies]
 windows-sys = { workspace = true, features = [

src/uu/du/src/du.rs

@@ -75,9 +75,6 @@ const ABOUT: &str = help_about!("du.md");
 const AFTER_HELP: &str = help_section!("after help", "du.md");
 const USAGE: &str = help_usage!("du.md");
 
-// TODO: Support Z & Y (currently limited by size of u64)
-const UNITS: [(char, u32); 6] = [('E', 6), ('P', 5), ('T', 4), ('G', 3), ('M', 2), ('K', 1)];
-
 struct TraversalOptions {
     all: bool,
     separate_dirs: bool,
@@ -117,7 +114,8 @@ enum Time {
 
 #[derive(Clone)]
 enum SizeFormat {
-    Human(u64),
+    HumanDecimal,
+    HumanBinary,
     BlockSize(u64),
 }
 
@@ -549,18 +547,14 @@ impl StatPrinter {
             return size.to_string();
         }
         match self.size_format {
-            SizeFormat::Human(multiplier) => {
-                if size == 0 {
-                    return "0".to_string();
-                }
-                for &(unit, power) in &UNITS {
-                    let limit = multiplier.pow(power);
-                    if size >= limit {
-                        return format!("{:.1}{}", (size as f64) / (limit as f64), unit);
-                    }
-                }
-                format!("{size}B")
-            }
+            SizeFormat::HumanDecimal => uucore::format::human::human_readable(
+                size,
+                uucore::format::human::SizeFormat::Decimal,
+            ),
+            SizeFormat::HumanBinary => uucore::format::human::human_readable(
+                size,
+                uucore::format::human::SizeFormat::Binary,
+            ),
             SizeFormat::BlockSize(block_size) => div_ceil(size, block_size).to_string(),
         }
     }
@@ -688,9 +682,9 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     });
 
     let size_format = if matches.get_flag(options::HUMAN_READABLE) {
-        SizeFormat::Human(1024)
+        SizeFormat::HumanBinary
     } else if matches.get_flag(options::SI) {
-        SizeFormat::Human(1000)
+        SizeFormat::HumanDecimal
     } else if matches.get_flag(options::BYTES) {
         SizeFormat::BlockSize(1)
     } else if matches.get_flag(options::BLOCK_SIZE_1K) {

tests/by-util/test_du.rs

@@ -543,6 +543,34 @@ fn test_du_h_flag_empty_file() {
         .stdout_only("0\tempty.txt\n");
 }
 
+#[test]
+fn test_du_h_precision() {
+    let test_cases = [
+        (133456345, "128M"),
+        (12 * 1024 * 1024, "12M"),
+        (8500, "8.4K"),
+    ];
+
+    for &(test_len, expected_output) in &test_cases {
+        let (at, mut ucmd) = at_and_ucmd!();
+
+        let fpath = at.plus("test.txt");
+        std::fs::File::create(&fpath)
+            .expect("cannot create test file")
+            .set_len(test_len)
+            .expect("cannot truncate test len to size");
+        ucmd.arg("-h")
+            .arg("--apparent-size")
+            .arg(&fpath)
+            .succeeds()
+            .stdout_only(format!(
+                "{}\t{}\n",
+                expected_output,
+                &fpath.to_string_lossy()
+            ));
+    }
+}
+
 #[cfg(feature = "touch")]
 #[test]
 fn test_du_time() {